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This thesis aimed to investigate cognitive and neural underpinnings of cognitive control in obsessive-compulsive disorder (OCD), focusing on suppression of thoughts and actions, cognitive flexibility, and habitual behaviour. Four experiments addressed hypotheses that, in comparison with appropriate control groups: (i) Patients with OCD are impaired in their ability to control actions as measured by the Stop-Signal/Go No-Go task; (ii) They also present deficits in attentional set-shifting in an extra-dimensional set-shifting task; (iii) OCD is marked by difficulties in the ability to control thoughts, as demonstrated by a Retrieval-Induced Forgetting (RIF) paradigm; (iv) Deficits in inhibitory control correlate with electroencephalographic markers, especially error monitoring and action tendencies; (v) Habitual and ritualistic actions in OCD are driven by both motor deficits and intolerance of uncertainty; (vi) Learning and practising a finger tapping sequence on a smartphone application (app) can have clinical benefits as a 'habit-reversal' treatment; and (vii) Metacognitive functions such as memory confidence and vividness are impaired in OCD, prompting the need to repeat actions. The thesis is structured in seven chapters, with experiments presented in chapters 3, 4, 5 and 6. Chapter 3 reports inhibitory deficits in a large group of OCD patients, showing impairments in action cancellation in this sample. These results are discussed alongside neural EEG markers and self-report measures, highlighting roles of error monitoring and enhanced action tendencies in the maintenance of OCD symptoms. Chapter 4 presents the results of a clinical trial conducted in collaboration with the NHS Highly Specialised OCD Clinic in Hertfordshire, where patients were randomised to either Treatment as Usual (TAU), a combination of Cognitive-Behaviour Therapy (CBT) and Exposure-Response Prevention (ERP), or Habit-Reversal Treatment (HRT). The latter consisted of a mobile phone application, and participants were asked to practise sequences of finger tapping movements. Participants were assessed at 3 timepoints (Baseline, Midterm and Endpoint). Results showed that HRT was equivalent to TAU in reducing symptoms, and indeed superior at enhancing quality of life in OCD. These results are discussed alongside neural markers and cognitive deficits in inhibitory control and extra-dimensional set-shifting. Chapter 5 presents data on a second group of patients with OCD and a matched control group, aiming to further clarify neural and cognitive dynamics of inhibitory control, error monitoring, and motor learning in OCD. For that end, both patient and control group were further separated into app and no-app training, enabling assessment of how the mobile application affects healthy participants, and whether the changes in OCD symptomatology seen in Chapter 4 were related to app training or to the passage of time. Electroencephalographic and behavioural data were collected at two different timepoints, separated by a month, to parallel the previous study and allow for comparisons. Chapter 6 further investigates inhibitory control deficits in OCD in an online study with yet another group of patients and control participants. The comparison between ability to control actions, as measured by the Stop-Signal Task, and thoughts, as per the RIF paradigm, showed significant RIF effects on controls, but not on patients, suggesting impaired thought inhibition in OCD. These results are discussed alongside a metacognitive memory test, which reveals the role of memory confidence as a possible cause of repetitive actions in OCD. A final Discussion (Chapter 7) brings together the findings of this thesis and considers their implications for the neuropsychological basis of OCD and its future treatment.

In linguistics, the relationship between word form and meaning is largely considered arbitrary. However, in literary works and in the broader discipline of literary theory, it is well acknowledged that word form is stylistically manipulated to link concepts and engage reader attention. Recent work in the field of neurocognitive poetics investigates how stylistic text influences semantic and attentional processes, but currently no research effort has focused on these effects in natural, declarative language. The empirical work presented in this thesis examines how phonological repetition in short phrases impacts upon semantic processing and attentional engagement, addressed in three main research questions: 1) How does phonological repetition between words affect semantic processing and attentional engagement? 2) How does phonological repetition between words affect semantic processing and attentional engagement in poor readers? 3) How does the relationship between sound and meaning affect memory? To this end, I constructed adjective-noun phrases, which were orthogonally manipulated for semantic congruency (congruent, incongruent), and alliteration (alliterating, non-alliterating), as in “dazzling-diamond”; “sparkling-diamond”; “dangerous-diamond”; and “creepy-diamond”. Over four experiments I establish that: 1) phonological repetition in the form of alliteration creates an illusion of meaning for typical readers, linking words beyond the level of actual semantic relatedness, 2) phonological repetition does not similarly impact readers with dyslexia at the neurocognitive level, though alliteration impacts their overt semantic relatedness judgements, and 3) the presence of alliteration does not improve recognition memory for word-pairs, but it does create a false sense of familiarity. Our findings show that, even in natural language, word form influences both online semantic integration and overt judgement and later memory processes.

There is a long-lasting debate as to whether mental imagery plays a functional role in cognition: one view states that mental imagery indeed plays a key functional role in cognitive processing, whereas other views suggest that propositional information is sufficient to complete a cognitive tasks and mental imagery is just an epiphenomenon. Recently, an alternative suggestion was proposed to reconcile these two hypotheses, namely that a range of strategies could be adopted to fulfil the demands of a given cognitive task. This thesis was motivated by the general question: What specific strategy could be adopted in cognition in terms of individuals differing in their visual imagery vividness. To this end, mental rotation (MR) tasks were used to investigate individual performance in mental imagery, both in behavioural experiments and event-related potentials (ERPs) studies. Participants were classed according to their vividness of visual imagery (VVI) as individuals with lower and higher VVI. In behavioural experiments, lower and higher VVI individuals were assessed with MR tasks with different task demands. Whereas no group difference were observed in processing simple objects, differential performance was observed in processing more complex visual stimuli: lower VVI individuals were more likely to use piecemeal transformation, whereas higher VVI individuals were found could automatically simplify the task by transferring partial representation of the visual stimuli in their minds' eyes. In the following ERP studies using a standard letters rotation task, longer MR execution time was observed in lower than higher VVI individuals. Rotation-related negativity (RRN) amplitudes were more pronounced in lower as relative to higher VVI individuals. In addition, the onset of RRN was found delayed in lower as compared to higher VVI individuals, while the onset of did not differentiate the two groups. These findings suggest that lower VVI individuals complete the MR process proper later than those with higher VVI. Higher VVI individuals are more able to generate simplified visual representations that can be easily rotated, whereas lower VVI individuals, who are more likely to create less accurate mental representations, might extract and represent additional information from the visual stimuli and therefore produce a longer MR execution time. M.X., an individual who reported the sudden loss of his visual imagery ability was also recruited for an ERP experiment with a standard letter rotation tasks. He performed as well as his age, sex, IQ-matched controls. In addition, he showed the typical linear pattern in RTs as did in his controls did. But differential performance was detected in ERP data. In mirror letters, RRN was detected in the control but not in M.X. This finding suggests that the imagery task could be completed in the absence of the visual representation. Interestingly, in processing normal letters, RRN was observed in both M.X. and the control group, supporting the idea that non-depictive representation could be generated and adopted in MR processing. In turn, this result suggest that RRN is a general index for MR processing, regardless of the format of the mental representation, depictive or descriptive. We then tested our hypothesis from another point of view by investigating whether one could adopt different strategies in MR tasks with different visual stimuli. Specifically, we explored which properties of the visual stimuli are more likely to predict the strategy selection in MR tasks. A behavioural MR experiment with polygon stimuli was conducted aiming at testing the two commonly used strategies used in MR tasks with different types of stimuli. Firstly, the segment number and the number of vertices in polygon stimuli were manipulated to test which property of the visual stimuli is more likely to influence the strategy selection in MR tasks. Secondly, the role of distractors was examined by comparing the stimulus complexity effect in both with- and without-distractors conditions. The results revealed that the number of segments affected the slope of the linear function relating response times to rotation angle but the number of vertices in the polygons did not. This suggests that a holistic strategy was more likely to be adopted in processing integrated objects, whereas a piecemeal transformation was at play in processing multi-part objects. In addition, the stimulus complexity effect was observed in the with-foil condition but not in the without-foil one, providing a direct evidence to support the role of distractors in MR tasks. We then supplemented the investigation of the use of different strategies to comply with MR tasks by further examining if the largely document ageing effect in MR tasks could be explained by strategy selection. Younger and older participants were assessed with a series MR tasks with different task demands. Their visual imagery vividness was controlled. In processing simple objects, the performance of the two age groups was comparable. However, systematic differences were observed between the mental rotation rates of younger and older adults while processing complex objects. Younger participants were faster in processing complex than simple objects, whereas older participants were slower in rotating complex than simple objects. These results revealed that different mental rotation strategies were selected by the two age groups. A simplified representation of the objects was generated and transformed by younger participants in their mind's eyes, while a piecemeal transformation strategy was adopted by older participants. In the ensuing ERP study with simple MR tasks using characters, age-associated slowing was observed in both behavioural and ERPs measures. While the RRN was already present in the early time windows in younger adults (350-500ms), it only emerged in the late time window (500-650ms) in older participants. Consistent with this observation, the onset of the RRN was delayed in older as compared to younger participants. These results suggest that MR processes occur later in older adults and demonstrate that the initial phase before MR proper is one source of the age-related slowing observed in MR tasks. Possible accounts for this age-associated slowing are a prolonged phase of stimulus encoding and/or selective difficulties in directing attention away from the external stimulus towards its internal mental representation. One more study was conducted to explore the general cognitive and neural mechanism underlying MR tasks. To better understand the normal-mirror difference in MR processing, we replicated Núñez-Peña and Aznar-Casanova's ERPs study (2009). The timing course of the planar rotation in normal letters, the planar and non-planar rotation in mirror letters were explored separately for each rotation angle. Moreover, we investigated the temporal relationship between these three processes for each angle. The result uncovered a complex cognitive process underlying MR process with mirror letters in which the non-planar rotation was found to occur at different time as relative to planar rotation for each rotation angle.

How we draw meaning from strings of letters is one of the most popular topics under discussion in cognitive science. Traditional theories posited that words represent amodal symbols and meaning is derived through their relationship to other amodal symbols (Galetzka, 2017). The problem with this cognitivist approach is that it was unclear how these symbols came to have meaning, known as the "grounding problem" (Harnad, 1990; Searle, 1980). Theories of embodied cognition were developed in an attempt to resolve this issue (Barsalou, 1999; Glenberg & Robertson, 1999). For example, the Indexical Hypothesis proposed that nouns are indexed to mental representations (such as mental pictures) of the objects they refer to (Glenberg & Robertson, 1999). Subsequently, when a noun is processed, the affordances (behavioural possibilities) of the referent object are made available (e.g., a mug affords being grasped by its handle). According to the Indexical Hypothesis, access to these affordances is crucial for noun comprehension (Glenberg & Gallese, 2012; Glenberg & Robertson, 1999). More recent theories of language comprehension posit that both amodal and embodied representations contribute to understanding (Barsalou, Santos, Simmons & Wilson, 2008; Louwerse, 2007; 2018; Louwerse & Jeuniaux, 2008). The present thesis discusses experiments using event-related potentials (ERPs), measured while participants read object names, in order to explore the timing of access to information related to these embodied representations of the referent objects. The first experiment revealed that the earliest information related to object affordance was available from 175 ms, soon after retrieval of lexical and semantic information begins (around 160 ms; Hauk, Coutout, Holden & Chen, 2012). Our second study revealed that functionally manipulable objects have a richer semantic representation, compared to objects that are graspable based purely on their geometric properties. Semantic processing of functionally manipulable objects incorporates knowledge about the actions associated with object use, perceptual information related to the object, and the specific motor programs necessary for manually manipulating the object. Actions associated with the use of functionally manipulable objects were accessed from as early as 190 ms. Affordances based on the geometric properties of an object were available from 224 ms and reflected pattern-matching between semantic information about the object's size and shape, accessed from processing the object name, with proprioceptive information provided by the participant's body, about the size and shape of the object they were holding during the experiment. Pulvermüller (1999) argued that sensorimotor representations of language are developed during our personal experiences in the world, through Hebbian learning. The findings of our final experiment supported this argument, indicating that the conceptual representation of objects, and the actions associated with their use, were developed during the participants' previous experience of using the object.

According to embodied accounts of human cognition, the mind is at the interface of the body and the environment. For practical reasons, however, neuroscientific research on human cognition has mostly been confined to the laboratory until now. The emergence of portable brain and body imaging research methods offers an unprecedented opportunity to capture the expression of cognitive processes during active behaviours performed in real-world contexts. In the present thesis, electroencephalography (EEG) was used to investigate embodied aspects of human cognition in motion and in the real-world. This approach, however, presents new challenges in terms of signal processing because of the increased noise related to whole body movements. As the necessary signal processing tools were not well-established, the current work involved the development of new solutions to address the specific requirements of mobile EEG data before real-world brain recordings could be validly interpreted. In a series of Event Related Potential (ERP) experiments, real-world conditions were compared to traditional lab-based conditions. The neural marker of attention (P300 ERP) was recorded when participants performed an attentional task while walking through the university's corridors versus standing in the lab. Differences in the classic P300 ERP effect show that attentional processes in the real-world are not the same as those recorded in the lab. Following up on this finding, the attenuation of the P300 effect under real-world conditions was shown to be driven by cognitive demands related to displacement through space rather than the act of walking itself. This is a demonstration, at a brain level, that when walking in the real-world, cognitive resources are reallocated to the processing of visual flow and vestibular information associated with displacement. The findings reflect the dynamic interplay between mind, body, and environment, providing innovative evidence strengthening the embodied framework of human cognition. The same dynamic interplay between body, environment and cognitive function is uniquely represented in real-world navigation. The literature on spatial navigation in humans, however, mainly involved navigating virtual reality environments often while lying on a scanner bed. Most of the evidence on the neural markers of spatial navigation comes from intracranially recorded brain oscillations in rodents. The innovation in this thesis was to investigate brain oscillations associated with cognitive function underlying real-world navigation in humans using surface electrodes. The present work demonstrates that human brain dynamics related to navigational cognitive processes can be recorded in active exploration of real-world environments. The key finding resulting from this novel approach is that real-world spatial navigation is associated with specific neural signatures underlying distinct cognitive functions. Frontal low-frequency oscillations were found to be associated with wayfinding, while parietal high-frequency oscillations were associated with spatial memory. Furthermore, these neural correlates were found to be dynamically modulated depending on the body's contextual positioning within the environment. Therefore, these findings again provide evidence in support of the embodiment theory of cognition. The final study addressed the concern that findings might reflect walking speed variation. The existing animal literature has shown that low-frequency bands are modulated by walking speed. This study characterised the specific modulations in spectral power as a function of walking speed in humans. Critically the pattern showed no similarity to the spectral patterns found in relation to real-world spatial navigation, confirming the cognitive interpretation of this work. Taken together, these findings provide innovative real-world evidence supporting the theoretical embodiment framework. The neural correlates of attention, memory, and spatial navigation were found to be modulated by the dynamic experience of one's environment. Beyond this work's theoretical implications for cognitive sciences, the present findings offer new perspectives for real-world application.

Affect and cognition have traditionally been considered mutually exclusive domains and their study has evolved into two separate research fields. In recent years, however, there is increasing evidence of affective modulations of cognitive processes and interest in the study of affective cognition has grown. This thesis presents analyses of data collected in four mixed-design experiments between 2009 and 2011, which were designed to investigate affective memory and its electrophysiological correlates, individual differences in said affective memory and electrophysiological correlates, the time-course of affective memory and attentional disengagement from affective stimuli respectively. The first aim of the research presented here was to further understanding of how affective content influences picture processing and memory. Event-related potentials (ERPs) provide a valuable tool for the investigation of modulations of cognitive processes, as their excellent temporal resolution allows for the dissociation between different processes contributing to behavioural outcomes. Several important results for the study of affective cognition are reported: The late positive potential (LPP) was shown to be modulated differentially by affective content when compared to a behavioural attentional disengagement task. While the behavioural measure of attention replicated findings from participants’ self-report of arousal, LPP enhancement did not. This novel finding demonstrates that the affective modulation of the LPP cannot be used as an electrophysiological marker of slowed attentional disengagement as is common in the literature. In the domain of recognition memory, affective modulation of performance was shown to be time-sensitive, with effects developing faster for negative than for positive picture content. Affective pictures were associated with a less conservative response bias than neutral pictures but only negative pictures elicited better discrimination performance, driven by an increased in the rate of “remembered” as compared to merely familiar pictures. This was reflected in an increase of the ERP old/new effect for negative pictures in the 500 to 800ms time window, the purported correlate of recollection. The late right-frontal old/new effect between 800 and 1500 ms post stimulus onset was shown to be attenuated by affective content, supporting the interpretation of the late right-frontal effect as a correlate of relevance detection over a retrieval success interpretation. In combination, the findings add weight to the conclusion that affective content enhances memory through selective memory sparing for affective stimuli. Novel evidence for gender differences in affective cognition was found. Comparisons between female and male participants revealed that the affective modulation of the late right-frontal effect differs between the genders, underlining the importance of assessing and understanding gender differences as part of the study of affective cognition. Brain-derived neurotrophic factor (BDNF) gene val66met single nucleotide polymorphism (SNP), a small genetic change that affects the functioning of BDNF, a protein that plays an important role in neuron growth, differentiation and survival, is shown here to also affect the interaction of affect and cognition. BDNF val66met genotype modulated the early “familiarity” old/new effect selectively in response to positive pictures. The present study clearly demonstrates the value of the ERP technique in the investigation of individual differences in affective and cognitive processing and the need to take such individual differences into account as part of the endeavour to fully understand the mechanisms of affective processing, cognition and affective cognition. A better understanding of the role of gender and genetic differences in the affective modulation of affective processing and memory will have important practical implications in fields where affect and cognition interact.

What are the effects of non-balanced bilingualism on cognitive performance? And how do proficient, non-native speakers acquire and use lexical, syntactic and semantic information during sentence processing? Whilst there is growing research on these topics, there is no firm consensus on how to answer these questions. In the literature on cognitive effects of bilingualism, this lack of consensus has even resulted in radically opposing views and a heated debate. In this thesis, I seek to provide a balanced treatment of the literature and to address the above-mentioned questions by employing behavioral and neurophysiological paradigms. First, using a structural priming paradigm, I examine how proficient, non-native speakers of different native language backgrounds (Romance and Germanic) acquire lexically-specific syntactic restrictions of non-alternating verbs in English. Results from these experiments suggest that, although non-native speakers partially acquire lexically-specific syntactic restrictions, their knowledge is not native-like. Moreover, transfer from the first language does not seem to play a role in the acquisition of the relevant restrictions. Second, using Event-Related Potentials (ERPs) I examine whether proficient non-native Spanish-English speakers draw on different forms of semantic information such as relatedness and animacy incrementally during sentence comprehension. Results of these experiments suggest that, while relatedness facilitates processing (indexed by N400s) in both native and non-native speakers, effects of animacy are smaller in non-native speakers, relative to native speakers. Third, I employ a series of auditory attentional tasks and measures of lexical access and verbal fluency to assess cognitive functions in non-balanced bilinguals with different levels of language proficiency. Results show a bilingual advantage in inhibitory control and a non-significant trend towards bilingual better performance in attentional switching, and the groups exhibit similar performance on verbal fluency. Results of all the studies are discussed in the context of the existing literature on cognitive performance in bilinguals and accounts of language processing in native and non-native speakers and suggestions for future research are provided.

The topic of this thesis is cognitive control: how the brain organises itself to perform the many tasks it is capable of and how it switches flexibly among them. Task-switching experiments reveal a substantial cost in reaction time and accuracy after a switch in tasks. This "switch cost" is reduced by preparation (suggesting anticipatory task-set reconfiguration), but not eliminated. The thesis focuses on the sources of the "residual" cost. Most accounts attribute it to response selection being prolonged on a task-switch trial by task conflict, e.g. by 'task-set inertia' — persisting activation/inhibition of the previous task's S-R rules — or their associative reactivation by the stimulus. Four experiments used event-related potentials (ERPs) to determine which stages of task processing are influenced by a change in tasks, looking for delays in process-specific markers in the ERP. Experiments 1 and 2 showed that a prepared switch to a reading task from a perceptual judgement delayed early ERP markers of lexical access by a large fraction of the RT switch cost, suggesting that a substantial part of the residual cost arises in processes earlier than response selection, possibly due to task-related attentional inertia. Markers of lexical access observed in the non-lexical task were larger on switch than repeat trials, providing the first electrophysiological evidence of task-set inertia. Experiment 3 examined the effects of an unprepared switch in the same way. ERP waveforms were modulated by a switch before markers of lexical access were evident, suggesting additional processing demands compete for resources with lexical access. A simple delay, however, was not found; post-stimulus task-set reconfiguration does not just insert an extra processing stage. Experiment 4 looked for a delay in the onset of an early ERP marker of emotional processing when the task switched between categorising facial expression and classifying a superimposed letter. No such delay was found in this case, and ERP markers of emotion processing were present to the same extent in the letter task. This suggests that, given appropriate spatial attention, processing facial emotion unfolds automatically, independent of attention allocation to the facial features. Experiments 5-7 further explored the link between conflict due to processing the irrelevant stimulus dimension and the ERP post-stimulus negativity that accompanies the residual cost. The negativity could be elicited even on trials of non-switching blocks by prior training on classifying the irrelevant attribute of the stimulus using the same responses. But this effect did not seem to result from the trained class of irrelevant attribute attracting more attention. Finally, Experiment 8 followed up an incidental observation in Experiment 1 to establish the novel observation that a task-switching context abolishes the usual ERP correlate of withholding a response in a go/no-go paradigm, suggesting an interesting interaction between task-set control and response inhibition.

Judgments of Learning (JOLs) are judgments of the likelihood of remembering recently studied material on a future test. Although JOLs have been extensively studied, particularly due to their important applications in education, relatively little is known about the cognitive and neural processes supporting JOLs and how these processes relate to actual memory processing. Direct access theories describe JOLs as outputs following direct readings of memory traces and hence predict that JOLs cannot be distinguished from objective memory encoding operations. Inferential theories, by contrast, claim JOLs are products of the evaluation of a number of cues, perceived by learners to carry predictive value. This alternative account argues that JOLs are made on the basis of multiple underlying processes, which do not necessarily overlap with memory encoding. In this thesis, the neural and cognitive bases of JOLs were examined in a series of four ERP experiments. Across experiments the study phase ERP data showed that JOLs produce neural activity that is partly overlapping with, but also partly distinct from, the activity that predicts successful memory encoding. Furthermore, the neural correlates of successful memory encoding appear sensitive to the requirements to make a JOL, emphasising the close interaction between subjective and objective measures of memory encoding. Finally, the neural correlates of both JOLs and successful memory encoding were found to vary depending on the nature of the stimulus materials, suggesting that both phenomena are supported by multiple cognitive and neural systems. Although the primary focus was on the study phase ERP data, the thesis also contains two additional chapters reporting the ERP data acquired during the test phases of three of the original experiments. These data, which examined the relative engagements of retrieval processes for low and high JOL items, suggest that encoding processes specifically resulting in later recollection (as opposed to familiarity) form one reliable basis for making JOLs. Overall, the evidence collected in this series of ERP experiments suggests that JOLs are not pure products of objective memory processes, as suggested by direct access theories, but are supported by neural systems that are at least partly distinct from those supporting successful memory encoding. These observations are compatible with inferential theories claiming that JOLs are supported by multiple processes that can be differentially engaged across stimulus contents.

This thesis investigates the effect of normal ageing on the strategies adopted during episodic memory retrieval, using a combination of neuropsychological profiling and neuroimaging data measured during performance on a source memory exclusion task. The exclusion task is a type of source memory task where participants distinguish between targets (studied items from one source e.g. female voice), non-targets (studied items from another source e.g. male voice) and new items. Unlike a source memory task where three separate buttons are pressed for each item at test, in the exclusion task one button is pressed for targets and a second for non-target and new items. As this task is more complex than a normal source memory paradigm and also allows participants to perform the task in more than one way, it places high emphasis on the use of strategies to facilitate retrieval and is therefore ideal for investigating strategic retrieval. Previous source memory studies have shown that while older adults are reasonably good at recognising whether items are old or new, they show marked impairments at remembering the source in which items were presented at study. Dual process theories propose that the age-related decline in source memory occurs because recollection becomes impaired with ageing whereas familiarity remains relatively spared. The results reported in this thesis support dual process theory. Experiment 2a showed that, behaviourally, as expected, the young outperformed the elderly. Event-related potentials (ERPs), recorded while a source memory exclusion test was performed, revealed that both young and older adults showed bilateral frontal and left parietal old/new effects, thought to index familiarity and recollection respectively. Importantly, the magnitude of the left parietal effect was significantly reduced in the older adults. The ERP findings also suggested that dual process theories represent an oversimplification of episodic memory decline with age. In Experiment 1a, three temporally and topographically distinct late frontal old/new effects were present in the younger adults: a bilateral anterior frontal effect (450-900ms post stimulus), a right prefrontal effect (900-1300ms) and a right frontal effect (1300-2000ms). Significant positive correlations between the magnitude of these effects and performance on neuropsychological tests of executive functioning in Experiment 1b, revealed that the bilateral anterior frontal effect was related to working memory, strategy use and planning; the right prefrontal effect was related to working memory and planning while the right frontal effect was related to planning. By contrast, the older adults in Experiment 2a only produced the right frontal effect, which correlated with planning across all three time windows in Experiment 2c. Post-retrieval monitoring in older adults therefore appeared to be qualitatively different than their younger counterparts. Performance on the neuropsychological tests in Experiment 2b, revealed that the older adults’ working memory and strategy use was impaired compared to the young, whereas planning was relatively intact, suggesting that age-related differences in post retrieval processing may be due to reduced executive functioning in older adults. Identifying distinct late frontal effects and demonstrating a relationship between these effects and specific executive functions is a novel finding. The presence of a left parietal target greater than non-target difference in the young adults from Experiment 1a and 2a was interpreted as the young reducing recollection of irrelevant non-target information. The modulation did not differ in magnitude for targets and non-targets in the elderly adults from Experiment 2a, suggesting they were less able to reduce activation of goal irrelevant non-target information. The results in the young adults from Experiment 1a also highlight the importance of considering the context of source information on the processes engaged at retrieval. The bilateral frontal effect was significant for the retrieval of the intrinsic context (source information inherent to the studied item), but not the extrinsic context (source information not inherent to the studied item). This finding was interpreted within a unitisation framework, where the intrinsic context became unitised with the item and enhanced familiarity based remembering. The findings also highlight that in order to fully understand post retrieval processing in both young and old adults, focus should move away from examining quantitative differences in the right frontal effect over long time periods and instead identify qualitatively distinct late frontal effects that may reflect the engagement of various executive functions over time.

Anxiety disorders pose a significant challenge to daily living, workplace productivity, and healthcare systems. Extant research supports empirical links between anxiety and brain-level error monitoring. The ERN – or error-related negativity – is one widely studied correlate of anxious symptomatology. Relatively stable individual differences in the ERN are inferred from electroencephalogram (EEG) recordings time-locked to the commission of mistakes. However, the assumed interchangeability of ERNs elicited under different experimental conditions has not been thoroughly evaluated. Canonical tasks for measuring the ERN may cue specific strategies for cognitive control, possibly producing divergent findings across studies. In a sample of 108 undergraduate students, we examined within and between-subject differences in the ERNs across three tasks. Experimental blocks alternated pseudo-randomly between several tasks: the AX Continuous Performance task (AX-CPT, Reactive Control), Go/NoGo (Inhibitory Control), and Navon-Flankers (Response Conflict). Partially consistent with our predictions, ERN mean areas for inhibitory control and reactive control trials were typically larger (i.e., more negative) than those for response conflict. Unexpectedly, the ERN was a non-significant predictor of Trait anxiety scores (STAI-T), after controlling for participant age and gender (all ps > 0.05). Future research should consider how ERN task parameters may obscure trait-level differences in error sensitivity.

The N400 and P600 components of cognitive evoked potentials or event-related potentials (ERP) are context related and usually recordable after a priming stimulus or context consisting of words or any meaningful stimuli. All studies previous to this one used a sequential presentation of stimuli to elicit the ERPs. In this study, however, the picture and word stimuli were presented simultaneously. ERPs were recorded from 79 neurologically normal subjects including 62 right-handed, 10 left-handed and 7 subjects who were suffering from temporal lobe brain damage. Subjects were either asked to respond as to whether the stimuli were congruent, incongruent or non-sensical (semantic incongruency) or as to whether they were 'new' or 'old' (recognition memory). The number of correct responses and the reaction time were both measured. ERPs were recorded using an electrode cap which consisted of 16-channel scalp electrode montage (an enhanced international 10/20 electrode placement system) with linked mastoids as reference electrodes. Data was acquired and analysed using Neuroscan signal averaging and mapping software. In all the experimental conditions studied the tasks were performed accurately but reaction time was significantly longer for the incongruent stimuli. The same occurred for 'new' items as opposed to 'old' items. In the ERP recordings the N400 and P600 components were independent. The N400 peak was recorded maximally over the frontal locations while the P600 was mainly a parietal component. Differences were observed in their latency, amplitude and spatial distribution within the various test conditions.

The reward positivity (RewP) is a feedback-related event-related potential elicited in response to reward with two distinct defining features. First, it reflects an axiomatic reward prediction error signal. Second, it is spectrally represented within the delta band. We propose a third defining feature, namely that it is an additive and temporally independent event-related potential feature. Across five datasets and ten studies, this dissertation tested three major hypotheses. First, we show that stimulus modality (e.g. visual and auditory stimuli) and parametric delays can shift the RewP in time, which empirically indicates an additive and temporally independent feature. Second, we provide some evidence that these shifts in timing can be elucidated with a computational model, lending credibility to our initial conclusions. Third, we show that our computational model can account for similar reductions in the RewP associated with sub-clinical depression. Taken together, our findings provide a viable third descriptor of the RewP that includes an additive and temporally independent dynamic.

Stimuli generated by a person’s own willed actions generally elicit a suppressed neurophysiological response than physically identical stimuli that have been externally generated. This phenomenon, known as sensory attenuation, has primarily been studied by comparing the N1, Tb and P2 components of the event-related potentials (ERPs) evoked by self-initiated vs. externally generated sounds. Sensory attenuation has been implicated in some psychotic disorders such as schizophrenia, where symptoms such as auditory hallucinations and delusions of control have been conceptualised as reflecting a difficulty in distinguishing between internally and externally generated stimuli. This thesis employed a novel paradigm across five experiments to investigate the role of agency and contingency in sensory attenuation. The role of agency was investigated in in Chapter 2. In Experiment 1, participants watched a moving, marked tickertape while EEG was recorded. In the active condition, participants chose whether to press a button by a certain mark on the tickertape. If a button-press had not occurred by the mark, then a tone would be played one second later. If the button was pressed prior to the mark, the tone was not played. In the passive condition, participants passively watched the animation, and were informed about whether a tone would be played on each trial. The design for Experiment 2 was identical, except that the contingencies were reversed (i.e., pressing the button prior to the mark led to a tone). The results were consistent across the two experiments: while there were no differences in N1 amplitude between the active and passive conditions, the amplitude of the Tb component was suppressed in the active condition. The amplitude of the P2 component was enhanced in the active condition in both Experiments 1 and 2. These results suggest that agency and motor actions per se have differential effects on sensory attenuation to sounds and are indexed with different ERP components. In Chapter 3, we investigated the role of contingency in sensory attenuation while using a similar ticker-tape design in Chapter 2. In the Full Contingency (FC) condition, participants again chose whether to press a button by a certain mark on the tickertape. If a button-press had not occurred by the mark, a sound would be played (one second later) 100% of the time (Experiment 3). If the button was pressed prior to the mark, the sound was not played. In the Half Contingency (HC) condition, participants observed the same tickertape; however, if participants did not press the button by the mark, a sound would occur 50% of the time (HC-Inaction) while if the participant did press the button, a sound would also play 50% of the time (HC-Action). In Experiment 4, the design was identical, except that a button-press triggered the sound in the FC condition. The results were consistent across both Experiments in Chapter 3: while there were no differences in N1 amplitude across the FC and HC conditions, the amplitude of the Tb component was smaller in the FC condition when compared to the HC-Inaction condition. The amplitude of the P2 component was also smaller in the FC condition compared to both the HC-Action and HC-Inaction conditions. The results suggest that the effect of contingency on neurophysiological indices of sensory attenuation may be indexed by the Tb and P2 components, as opposed to the more heavily studied N1 component. Chapter 4 also investigated contingency but instead used a more ‘traditional’ self-stimulation paradigm, in which sounds immediately followed the button-press. In Chapter 4, participants observed a fixation cross while pressing a button to generate a sound. The probability of the sound occurring after the button-press was either 100% (active 100) or 50% (active 50). In the two passive conditions (passive 100 and passive 50), sounds generated in the corresponding active conditions were recorded and played back to participants while they passively listened. In contrast with the results of Chapter 3, the results of Chapter 4 showed both the classical N1 suppression effect, and also an effect of contingency of the N1, where sounds with a 50% probability generated higher N1 amplitudes compared to sounds with 100% probability. In contrast, Tb amplitude was modulated by contingency but did not show any differences between the active and passive conditions. The results of this study suggest that both sense of agency and sensory contingency can influence sensory attenuation, and thus should be considered in future studies investigating this theoretically and clinically important phenomenon.

Given the prominent role of anxious arousal in the development of anxiety disorders, it would be useful to understand risk factors predicting anxious arousal. A promising risk factor is emotional dysregulation (ED), or the maladaptive processes through which individuals modulate their emotions consciously and unconsciously to respond to environmental demands. To reduce the risk of biased measurements and enhance the understanding of neurobiological underpinnings, researchers have called for the adoption of a multimethod approach to ED. The use of biological correlates of ED, such as the late positive potential (LPP), may be key in extending the understanding of this construct. The current study examined whether ED, measured by the Difficulties in Emotion Regulation Scale and unpleasant images LPP amplitude, predicted anxious arousal (measured by the anxious arousal subscale of the Anxiety Depression Distress Inventory-27). The sample comprised 67 community participants (M age = 29.1, SD = 12.2; 61% female; 36% meeting for Diagnostic and Statistical Manual of Mental Disorders diagnosis; DSM-5) enrolled in a study examining anxiety using experience sampling. Self-reported ED and unpleasant images LPP amplitude were used as predictors in two hierarchical linear regressions. There were significant positive relations between self-reported ED and anxious arousal, β = 0.26, F(1, 64) = 4.98, p = 0.03. There were no significant relations between neurophysiological ED and anxious arousal, β = 0.03, F(1, 62) = 0.06, p = 0.811. There are several potential explanations for the lack of convergence between the DERS-SF and unpleasant images LPP amplitude. It may be that there are inflated relations between the DERS-SF and anxious arousal due to common method variance. Alternatively, images used in the emotional picture paradigm may not have elicited ED strongly enough in this study, or the LPP may have been incorrectly indexed as a neurophysiological measure of ED.

During scene perception, studies have shown the importance of the global distribution of a scene. Electrophysiological studies have found these global effects concentrated corresponding to the second positive and first negative peaks (P2 and N1, respectively) of the Event-related potential (ERP) during the first 600 ms of scene perception. We sought to understand in Experiment 1, to what extent early responses to scenes were driven by mid-level global information such as the degree of naturalness or openness in a scene image in the absence of specific low-and high-level information (color and semantic object detail). This was done using artificially-generated stimuli controlling for two global scene properties (GSPs) of spatial boundary and naturalness while minimizing color and semantic object information. Significant effects were observed on the P2 and N1 components as well as the P1 component. However, the question of whether scene perception is dominated by global or local factors had yet to be answered leading to Experiment 2. During Experiment 2, for half the trials scenes were presented in an inverted orientation. We found only an orientation interaction approaching significance corresponding to the P1 time course.

The visual system continuously adjusts how it responds to current stimulus based on the history of the incoming stimuli, a process referred to as visual adaptation. Most of the previous studies focused on short-term adaptation effects ranging from milliseconds to minutes. Recent work has showed behavioral effects of long-term adaptation (hours and days), but their neural mechanisms remain unexplored. We aimed to uncover the neural bases of long-term orientation-specific contrast adaptation in an electroencephalography (EEG) experiment. Subjects were deprived of vertical contrast for 4 hours using altered reality goggles, which filtered out vertical energy from the scene in real-time. Event-related potentials (ERPs) in response to vertical and horizontal gratings were recorded before and after the long-term deprivation. We hypothesized that ERP response to vertical stimulation would increase in strength, and might decrease in latency, after the long-term deprivation. Results were analyzed by computing simple amplitudes of response, by comparing model fits to the ERP time courses, and by using the spatial pattern of ERP responses to classify trials by stimulation type. Early ERP components in response to vertical increased in amplitude and decreased in latency following adaptation, relative to responses to horizontal, but these differences were not significant. However, model fitting and classification results both revealed significantly greater differences in ERP responses between vertical and horizontal stimulation following adaptation. Collectively, these results suggest that long-term adaptation changes the amplitude of response in early visual cortex.

Languages can be divided into two types based on how they express motion events. Some languages, like English, tend to express manner of motion in the verb and path of motion outside the verb. Other languages, like Spanish, tend to express path of motion in the verb and only express manner rarely in subordinated or separate clauses. Behavioral research has examined whether these differences in expression lead to crosslinguistic differences in the sensitivity to manner versus path information in cognition; however, these studies have led to inconclusive results. To date, no study has examined the neural correlates associated with either the lexicalization of motion information nor to the sensitivity of motion information processing. As such, the current study examines the event-related potentials (ERPs) associated with the processing of grammatical but atypical patterns of lexicalization and sensitivity to violations of expectancy for motion expression (congruency with a preceding animation) in adult native speakers of English and Spanish by examining the N400 (marker of semantic expectancy) and the P600 (marker of syntactic congruity that has recently been implicated in certain semantic errors). I predicted that atypical lexicalization patterns would produce larger ERP effects compared to typical patterns, and ERP effects would be larger for motion information to which speakers were more sensitive. Rather than the traditionally predicted N400 effects to atypical lexicalizations, the results showed greater P600 effects. Similarly, analyses of sensitivity to motion expression violations revealed greater P600—as opposed to N400—amplitudes in response to incongruent compared to congruent motion verbs in both languages as well as both an N400 and P600 effect in path prepositions in English. In contrast, manner expressed outside the verb (gerunds) in both languages and path expressed outside the verb in Spanish (prepositions, adverbs) produced the traditional N400 effect for incongruent compared to congruent expressions. While these results do not provide support for the idea that habitual expression increases sensitivity to that type of information, it does suggest that speakers are sensitive to those lexical patterns. More interestingly, it suggests that the P600 may be sensitive to a broader range of stimuli than previously predicted.

Structured Sequence Processing (SSP) is a fundamental, general-purpose neurocognitive mechanism used to learn patterns of information in the environment over time. SSP helps us make predictions about upcoming events and is vital for grammatical language processing. The primary aim of my doctoral research is using cognitive training techniques with brain imaging to better understand and to improve attention and learning mechanisms that support (and could, in turn, enhance) language. The focus has been on SSP and grammatical/predictive language processing. To summarize main findings across three studies, 1) the results from a mediation analysis (N=60) demonstrate that computerized SSP training has an underlying effect on predictive language processing by way of its effect on SSP, 2) the results from source localization of electrophysiological activity in the brain (N=32) suggest the neurocognitive mechanisms recruited for a non-linguistic SSP task and a grammatical language processing task share marked overlap in the left anterior superior temporal gyrus, and 3) the preliminary findings of a second computerized SSP training study with EEG/ERP recording (N=34) establish the feasibility of improving SSP as a way to improve language, possibly modulated by changes to attention and working memory. These outcomes inform future investigations of how SSP and language mechanisms can be enhanced in individuals with atypical SSP and language processing, either developmental or acquired. This approach could lead to collaborative opportunities for exploring the potential to improve SSP and language by functionally reorganizing their shared neural circuitry.

The problem of selecting an appropriate representation for a given dataset is a critical first step in the analysis process. By making use of a particular model, the researcher places an often-unstated set of assumptions on the shape, or functional form, of the data. Sometimes the chosen model and its assumptions may lead to incorrect conclusions, or not even answer the underlying research question. This dissertation explores ways in which model specification is done in practice, the effects it has, and what we can do to address problems with current approaches. Time series data, particularly biological, are becoming increasingly common as we explore the relationship between biology and behavior. Event-Related Potentials (ERPs), which are brain responses to time-locked stimuli measured using Electroencephalography (EEG), are one example of such data. The goal in ERP research is to make inferences about neural circuits and mechanisms used when responding to stimuli. We first discuss a methodological divide in this context that leads to both interpretation differences and differences in the underlying distributional theory for testing. Through both analytic work and simulation study, we explore the properties of two competing metrics for ERP component amplitude. This study leads to a suggestion that treating the data-generating model as an analysis framework could provide a major step toward a unifying framework that facilitates reproducible research. Our framework can draw from the substantive expectations researchers have about the shape of individuals' waveforms, particularly in local regions of interest, and translate these verbalized assumptions into mathematical basis sets. These assumptions allow us to derive properties of the representative waveform and implement them as parameters of a statistical model. We then test hypotheses on landmark parameters of the basis sets via multilevel modeling, which allows us to account for temporal patterns, patterns across channels, individual differences, and differences across experimental conditions. Biological contexts are not the only areas for applications of this basis set approach. Using an example from statistics education, we show that Item Characteristic Curves (ICC) from Item Response Theory (IRT) can also be conceptualized as basis sets, with interpretable parameters that are reflected in the shape of the resulting curve. This context also provides a venue for shifting the current paradigm of using established models without considering the underlying assumptions that they represent - introductory statistics courses. This work is incorporated into a more general paper on statistics education where we contrast a traditional method of analysis with the basis set approach presented here. We believe that by emphasizing the process of selecting a correct model early in methodological training, we can encourage scientists to be receptive of models that test their hypotheses directly and to begin incorporating the process of creating these models into their standard practice. Overall, the collection of three papers assembled in this dissertation makes the following contributions: identification of a methodological divide in ERP research and exploration of the properties of two competing metrics, description and demonstration of how basis sets can be designed with meaningful landmarks as parameters, highlighting of additional uses for such basis sets, and emphasis on the value of methodological training for interdisciplinary awareness of the importance of model selection.

Adult psychopathic offenders show an increased propensity towards violence, impulsivity, and recidivism. For a subsample of youth with elevated psychopathic traits, the disorder appears to remain stable throughout development. Such youth represent a particularly severe subgroup characterized by their extreme behavioral problems and comparable neurocognitive deficits as their adult counterparts, including perseveration deficits. Here, we investigated error-related processing using two distinct neuroimaging methodologies in response-locked event-related potentials (ERPs) and functional magnetic resonance imaging (fMRI) in two samples of incarcerated juvenile male offenders who performed a response inhibition Go/NoGo task. Adolescent psychopathic traits were assessed using the Hare Psychopathy Checklist: Youth Version (PCL:YV). In Study 1, PCL:YV scores were unrelated to the error-related negativity (ERN/Ne) amplitude linked to early error-monitoring processes, but were negatively related to error-related positivity (Pe) amplitude, reflecting later stages of error-related processing. In Study 2, PCL:YV scores were negatively associated with hemodynamic activity in subregions encompassing the basal ganglia, including the caudate, nucleus accumbens, globus pallidus, subthalamic nucleus, and substantia nigra during error-related processing. These two studies support the attentional bottleneck theory, whereby adolescents with elevated psychopathic traits devote attentional resources to early error-related processing, but exhibit a specific deficit in allocating attentional resources to further processing of error-related information, including the motivational significance of such information to ongoing behavior. These two studies provide the first evidence to suggest that youth with elevated psychopathic traits do not process error-related information effectively, which could potentially help explain this population’s increased propensity towards negative outcomes including recidivism.

Abstract: Background. Context use in sentence comprehension is fairly resistant to age-related cognitive decline; however, event-related potentials (ERPs) studies have shown age effects in neural activity associated with sentence comprehension, specifically when contextual information is manipulated. One well-documented ERP component, N400, may reflect the use of context to predict upcoming words. Older adults have smaller and later N400 responses than younger adults for unexpected sentence-endings (Federmeier et al., 2002), suggesting age-related differences in how adults use context. As well, there is the post-N400 positivity (PNP) – both at the frontal and parietal regions - that may index attempted re-analysis of incongruent sentences, or reflect predictive processing, which is also influenced by age (Van Petten & Luka, 2012). The purpose of the present study is to determine whether there are age-related differences in reading comprehension of sentences with varying semantic anomalies, using electroencephalography methods. Methods. Experiment 1 was designed as a pilot study, to investigate whether a passive reading paradigm would elicit the anticipated ERP responses. In Experiment 1, neurologically healthy young adults (n = 34; age range 18 – 30 years, M = 23.8, SD = 3.05) passively read pairs of sentences while wearing an electroencephalography cap. In Experiment 2, EEG was recorded while young (n = 22; age range 18 – 27 years, M = 21.1, SD = 2.62) and older (n = 21; age range 50 to 84 years, M = 62.0, SD = 8.98) adults read the same pairs of sentences as in Experiment 1, followed by a recognition memory task where they had to identify the presented sentence-ending word in order to elicit active processing of the stimuli. In both experiments, the reading task consisted of the presentation of two sentences. The first sentence established the context. The second sentence ended with a target word that was either 1) expected, 2) unexpected but semantically related, or 3) unexpected and unrelated to the context. The amplitude and latency of the N400 and PNP were measured using electroencephalography for the final target word, in each experiment. Reading time and recognition memory accuracy (Experiment 2) was also measured. Results. In Experiment 1, there was no significant N400 effect for the three sentence ending conditions. However, we detected a parietal PNP response in terms of mean amplitude. In Experiment 2, there were no significant differences in the behavioural measures between young and older adults (reading time and memory performance), as anticipated. Younger and older adults demonstrated maximal N400 responses for unexpected-unrelated words and minimal N400 responses for expected words. The latency of the N400 response was different between the groups, in which older adults had delayed processing in the earlier time window. Both groups of adults also demonstrated parietal post-N400 positivity (PNP) responses, contrary to previous literature. Discussion. Younger and older adults performed similarly on behavioural measures and the N400 results indicated that older adults are able to use their semantic memory to assess the stimuli features similar to young adults. However, there was evidence for age-related differences in the N400 latency. The parietal PNP responses also showed differences in the processing of the stimuli between young and older adults. Overall, our findings are important for understanding the neural correlates underlying age effects on context use in sentence comprehension. As reading plays a vital role in our society, understanding how aging affects this ability will provide new insights into the corresponding neural mechanisms, with possible implications for clinical populations with reading impairments.

Abstract: Driving is a complex task that requires a high level of attention for the safe operation of a motor vehicle. However, the human attention system is limited in capacity, and distraction arises when there is a competition for attention from non-driving related activities. When insufficient attention is prioritized to the road ahead, driving safety may be undermined. Cognitive distraction, one form of driver distraction, occurs when attention is withdrawn from the primary task of driving to a competing cognitive event. In this dissertation, I implemented four studies involving behavioural and electrophysiological methods to expand our current understanding of the impact of cognitive distraction on driver attention and performance. The first three studies focused on the emotional side of cognitive distraction, while study four focused on the social and cognitive influence of an in-car passenger. Study one aimed to examine the potential for driver distraction from emotional information presented on roadside billboards. To achieve this, participants operated a driving simulator in the presence of positive, negative, and neutral words. Study two investigated the behavioural and event-related potential (ERP) effects elicited by auditory words of different emotional valence (positive, negative, and neutral) during driving (dual-task) and non-driving (single-task) conditions. The primary goal was to determine whether distraction presented in the auditory modality would produce a similar pattern of effects as visual distraction. The secondary goal was to assess the allocation of neural resources under single and dual-task conditions. Study three aimed to examine the effects of highly arousing taboo-related distraction on driving performance. Participants operated a driving simulator in the presence of non-arousing words, moderately arousing positive and negative words, and highly arousing taboo words, presented on roadside billboards. Study four examined the attentional effects of driving with an in-car passenger, using electrophysiological methods. The objective was to investigate the relationship between attention, cognitive load, and social demands, related to the presence of a passenger. Findings from the first three studies provided novel insights and significant contributions to the literature on driver distraction by: (a) providing evidence that emotion-related distraction can capture and modulate attention to impact driving behaviour, (b) providing evidence that the processing of emotional information while driving likely influences higher-order cognitive processes rather than lower level sensory and perceptual processes, and (c) providing evidence that driving performance is differentially influenced by the valence (positive vs. negative) and arousal (high vs. moderate) of the emotional content; these unique effects reflect separate processes in the attention system, related to how arousal and valence interacts. Study four provided novel insights and significant contributions to the driving literature by: (a) providing evidence that mere presence of a passenger is sufficient to consume driver attentional resources, (b) supporting research in social psychology that describe the social influence of others, and (c) providing evidence that a potential mechanism for the effects of passengers is that they impose additional cognitive demand on the driver’s limited resources. Together, these convergent lines of research demonstrate that a main element of cognitive distraction is increased driver workload, which can modulate attention to influence driver attention and performance.

Where a reader's eyes fixate within a word influences how accurately and quickly a word is recognized. Mapping performance against fixation within a word gives the “viewing position (VP) curve,” which has an inverted-U shape with better recognition at word beginning than end and best recognition at a fixation slightly left-of-center (optimal viewing position, OVP). There are data supporting each of the major, non-mutually exclusive accounts of these VP asymmetries: informativeness, cerebral laterality, and perceptual learning. However, none of them can explain why reverse VP asymmetries have not been observed. It is my thesis that these issues are in large part because stimulus and reader characteristics both are critical in visual word recognition. We addressed the issues by using a target discrimination task in a VP paradigm for a variety of more-or-less word-like strings. Behavioral results show (1) all strings yield an U-shaped VP curve; (2) all but strings with no letter-like features show a beginning-vs-end VP asymmetry, ruling out an account based wholly on either informativeness or left cerebral specialization for word processing; (3) only words exhibit a left-to-center OVP, suggesting cerebral laterality and/or informativeness may play a role; (4) perceptual learning also falls short of explaining the deleterious effect on performance of the number of characters in the target's VF (i.e., visual crowding). Using event-related potentials, our investigation on the neural mechanisms of the VP effects find (1) the continuity of fovea to parafoveal processing assumption, required for the cerebral laterality account, however, interacts with VF, and (2) an electrophysiological index of the OVP effect in the early sensory P1 component. Compared to prior research, we use a broader range of stimulus types, at more locations in visual space, in a target discrimination task, thereby affording a not only finer-grained analysis of the VP curve but also filling significant empirical gaps. For the first time, we dissociate the beginning-vs-end and OVP asymmetries, and further uncover an important role for an unexamined factor: visual crowding. Moreover, by filling these empirical gaps, we provide additional constraints on any empirically adequate account and conclude that no current alternative is wholly satisfactory.

At its core, word learning and recognition concerns a relation between a low-level acoustic signal and a high-level semantic representation. Fundamental to the study of the early lexical-semantic system is the manner and degree to which the acoustic signal activates the semantic representation, and how meanings associated with words relate to one another. An implicit notion in the developmental literature is that upon hearing a word, young children activate the corresponding semantic representation in a dichotomous fashion – i.e., the semantic representation is either activated resulting in word recognition or not activated resulting in lack of recognition. Further, it is not entirely known the degree to which very young children appreciate that word referents are meaningfully related. To date, models of early auditory-semantic processing are primarily based on studies of meaningful relations between words and referents. However, lexical information (i.e., words) is not the only type of auditory input that is meaningful – environmental sounds (e.g., dog barking or pen scribbling) are nonverbal yet complex sounds that carry deep semantic associations with a corresponding referent. Therefore, a thorough investigation into the fundamental relation between acoustic signals and meaning requires an understanding of how meaning is associated with both lexical and non-lexical sounds. A series of four studies with toddlers and adults are presented to investigate three related issues in the study of early auditory-semantic development: 1.) Is lexical knowledge dichotomous or continuous? 2.) How is lexical information semantically processed and organized? 3.) To what degree is such processing specific to language? In the first set of studies, Chapters 2 and 3 present behavioral evidence that early word recognition is not binary, but instead graded, and partial knowledge plays a role in future learning. In the second set of studies, Chapters 4 and 5 replicate and extend findings that suggest the lexical-semantic system is organized as an interconnected semantic network both early in life and into adulthood. Further, these chapters present evidence that the electrophysiological markers of semantic processing are present during environmental sound processing in toddlers and adults, however words and environmental sounds appear to be organized somewhat differently, with a more consistent fine-grained structure for words compared to environmental sounds. Together, these studies provide behavioral and electrophysiological evidence to further our understanding of the nature of the early auditory-semantic system.

This study examined age-related differences in processing emotionally valenced objects. Previous studies with younger adults have found that negatively valenced stimuli, such as threatening objects, attract attention involuntarily compared to positively valenced stimuli. The authors suggested that the rapid detection of threatening stimuli has potential adaptive value. The present study was therefore designed to provide the possibility of obtaining converging evidence for this claim using both behavioral and electrophysiological measures. In addition I examined in the present study whether or not the involuntary capture by emotionally valenced objects would be observed in older adults. The cuing paradigm used by Lien, Taylor, and Ruthruff (2013) was applied in the present study. Participants identified the gender of a fearful face in the display. Preceding the target, two cues were presented one emotional [threatening or positive] and one neutral) for 125 ms. The emotional cue was presented either in the same location as the target (25% of the trials; valid) or in a different location (75% of the trials; invalid). Thus, there was no incentive to allocate attention to the emotional cue. The event-related potential (ERP) component of N2pc was used to index spatial attention. The ERP and behavioral data using the Cue-Validity paradigm strongly support that the emotional cues captured attention.

Event-related potential (ERP) studies are a subset of experimental frameworks within the field of electroencephalography (EEG) that focus on ERPs, the electrical potential outputted by a subject's brain when presented with an implicit task in the form of stimuli. Data comprise an ERP repetition observed for each stimulus across electrodes on the scalp, producing a complex data structure consisting of a functional, longitudinal and spatial dimension. In typical ERP studies, the dimension of data is reduced into a single measure for each subject by cross-sectionally averaging ERP across longitudinal and spatial repetitions. Features are then extracted from the averaged ERP and analyzed using simple statistical methods, ignoring additional information that may be found in the collapsed dimensions. In this dissertation, three types of methodology are proposed for preserving and analyzing the lost dimensions of ERP data. The first method, moving average processed ERP (MAP-ERP), is a two-step approach comprised of a meta-preprocessing step to preserve longitudinal information and a weighted mixed effects regression framework to allow modeling of the resulting meta-preprocessed data. The proposed robust functional clustering (RFC) algorithm identifies substructures in features of the longitudinal ERP processes while accounting for subject-level covariance heterogeneity induced by meta-preprocessing. Finally, the proposed multidimensional functional principal components analysis (MD-FPCA) utilizes a two-stage procedure to summarize important characteristics across all three dimensions of the ERP data structure into an interpretable, low-dimensional form. Proposed methods are applied to a study on neural correlates of visual implicit learning in young children with autism spectrum disorder (ASD). Applications of the proposed methods reveal meaningful trends and substructures in the implicit learning processes of ASD children when compared to typically developing controls. Results indicate proposed methodology effectively preserves important information contained within the multiple dimensions of ERP.

Demonstratives are lexical forms that pick out an object by making use of constraints in a discourse context to establish some form of contrast. They represent among the most basic uses of language, yet escape simple definition. The two forms gthish and gthath in English, the three forms ,± gko,h ,» gso,h , gah in Japanese, etc. have traditionally been interpreted in terms of relative distance from the speaker or hearer to the object. An alternative framework presents demonstratives as a device to refocus attention (e.g., Strauss, 2002), where gthish requires more of the hearerfs attention, to represent new information, or to refer to objects relatively important in the discourse, versus objects called gthath or gith. However, distance or attention alone is an insufficient parameter to predict form selection. This dissertation builds upon Brovold and Grushfs (2012) analysis of demonstratives in terms of control over an object. I propose that demonstrative forms, at least in English and Japanese, can be predicted from an array of control spaces that allow for varying levels of potential action toward an object. The proposed framework of control spaces implies an embodied view of language, such that language and physical behavior work toward shared goals and link mature human language use to other forms of animal communication, to child language acquisition, and with adult humansf response to a changing environment (De Ruiter, 2006; Melinger & Levelt, 2005).The control space framework incorporates previous models and makes three specific predictions. First, relative distance serves as one determinant for demonstrative form selection. Second, the weight of relative distance in demonstrative form selection will decrease without shared eye gaze between the speaker and hearer. 3. Demonstrative use would show as a tendency greater dependency on the co-speech pointing gesture for speakers of a language (e.g., English) that has fewer demonstrative terms than another (e.g., Japanese). To evaluate the three predictions, two perceptual studies that employed behavioral and event-related potential (ERP) measures were conducted to assess language usersf intuitions and cortical-level neural responses to the presentation of demonstrative expressions in differing visual contexts. When the simultaneous visual context with demonstrative expressions did not correspond with expected relative distances among speaker, hearer, and object, participants responded with significantly longer reaction times accompanied by a brain response called the N400, which is associated with semantic/contextual incongruities (Kutas & Hillyard, 1980, 1984). The elicitation of the N400 response for the incongruent audiovisual matchup in demonstrative use depended on shared gaze between the speaker and hearer, and the N400 responses were found in both English and Japanese subjects. English and Japanese subjects, however, differed in their responses to trials that did not include a pointing gesture in the visual scenes. In the absence of co-speech pointing gesture, English speakers expressed a P600 response, an index of pattern violations, but Japanese speakers did not. These findings indicate that in addition to spatial distance, language users rely on shared gaze in determining the proper use of demonstrative forms and show language-specific sensitivity to the presence or absence of gesture when analyzing demonstratives.The results of this dissertation project highlight the contingent, contrastive, and attention-orienting nature of demonstratives and further illustrate the necessity to study speech communication as a multimodal social event, which is subject to a number of factors, including perspectives of the speaker and listener, physical context, gesture, and language per se. Demonstratives function as basic lexical means to make meaning out of the world. They represent a special case of names, which are interpreted here as deictic means to form an object out of a nameless ground. Demonstratives, more specifically, serve as names that are used once and then no longer refer to the same object, resuming the naming practice with every use. The ERP results reported in this dissertation show promising brain signature markers for understanding the multimodal processing nature of spatial demonstratives. Further directions for research are suggested, including measuring the relationship between autistic individualsf competence with demonstratives alongside their imitative physical skills.

This study served to further investigate learning and memory, and to offer a potential tool to support educational interventions. More specifically, this was accomplished by an investigation of the physiologic changes in the brain that occurred while students learned medical anatomy. A group of 29 students taking the Gross Anatomy course at Boston University School of Medicine participated in the study. Testing occurred in two sessions: prior to the course and at the completion of the course. For each session, scalp EEG was recorded while participants were shown 176 anatomical terms (132 relevant to the course and 44 obscure) and asked to respond with "Can Define", "Familiar", or "Don't Know". Behavioral results indicated a positive correlation between participants' course grades and performance on the experimental tasks. EEG results were analyzed for event-related potential (ERP) components related to two memory components: familiarity and recollection. Results had a number of indications. For Don't Know responses, a stronger early frontal, late parietal, and late frontal effect occurred more so for terms of Session 1 compared to Session 2. For an analysis of just Session 2 data, results indicated increased activity of the early frontal, late parietal, and late frontal effects for Can Define responses only. Session 2 Can Define responses elicited a stronger early frontal ERP, occurring between 300 and 500 milliseconds yet, the most post-retrieval processing and monitoring appeared for Can Define terms of Session 2. Ultimately, we focused on investigating two points: 1) the effect of classroom learning on memory, and 2) the examination of ERPs as a tool to guide education interventions. Specifically, ERPs would potentially indicate markers to predict whether students would retain materials long before behavioral measures indicate these results. This has potential to determine whether long-lasting or transient learning will occur; as well as the potential to support early intervention strategies for not just students, but also individuals with learning disabilities or memory impairments.

Children reared in the deprived environments of institutions (e.g., orphanages) are at increased risk for problems with inattention and hyperactivity. Although these children have been reported to have higher rates of Attention Deficit/Hyperactivity Disorder (ADHD) diagnoses than would be expected in the general population, it is unclear if ADHD among post-institutionalized (PI) children is different from that among never institutionalized children. This study directly compared the clinical and symptom profile, executive function task and delay aversion task performances, and event-related potentials of 11- to 15-year-old internationally adopted PI children with ADHD (PI-A) to PI children without ADHD (PI-N) and non-adopted children with ADHD (NA-A). PI-As were found to be adopted primarily from Eastern European countries following longer periods of institutionalization than PI-Ns. They performed more poorly on most of the behavioral measures of executive function than PI-Ns; although the performance generally did not differ from NA-As. Relative to NA-As specifically, PI-As reported elevated disinhibited social behavior and, among males, demonstrated more aversion to delay, and had smaller overall N2 amplitude associated with a Go/No-go task. The results indicate that deprivation-related ADHD has an overlapping clinical profile with standard ADHD in addition to a few unique features. This profile associated with early deprived care could be considered a phenocopy of standard ADHD. A description of the deprivation-related ADHD profile has potential implications for identification and treatment of ADHD behaviors among PI youth.

Objective: This dissertation explored the neurophysiological correlates of lifetime externalizing (EXT) spectrum disorders in two studies using a community-based sample of 29-year-old adult men assessed longitudinally. The first study used high-density EEG brain data to test the hypothesis that reductions in time-domain and time-frequency component measures previously identified in 17-year-old youth with EXT continue to be present in adults at age 29 when participants have largely passed through the age of heaviest substance misuse, and when brain development is further complete. The second study tested the notion that reductions on these brain measures could serve as endophenotypes (or inherited biomarkers) for EXT risk by investigating the developmental stability of these associations across a 12-year span. We further uniquely tested whether significant reduction in time-domain P3 amplitude could be used to predict the eventual diagnosis of an externalizing disorder over a decade later. Method: In both studies, EEG data were obtained using a visual oddball task. Participants were assessed from age-17 through age-29 for the lifetime presence of EXT disorders. The first study used data from 378 male twin participants from the original 17-year-old cohort of the Minnesota Twin Family Study (MTFS) who had high-density EEG data that allowed for regional scalp analyses, including data from the frontal region that was not available before. The second study included the same 29-year-old males who had EEG data collected from a midline parietal site (site-Pz) at both their age-17 and age-29 assessments (n = 325). All comparisons were made against controls free of any EXT diagnosis by age 29. Results: The hypothesis tested in the first study was supported with both time-domain and time-frequency components coinciding with P3 activity significantly reduced across all EXT groups, particularly at the posterior regions. Furthermore, a theta time-frequency component yielded frontal discriminations that were not apparent in the time-domain. Hypotheses from the second study were also confirmed with group results demonstrating reductions in these brain measures across all EXT groups with comparable effects observed at both age-17 and age-29. Finally, P3 amplitude at age-17 was predictive of EXT status by age-29 with every one-microvolt decrease in P3 amplitude associated with an approximately 5% increase in risk for an age-29 EXT diagnosis. In both studies, the effects of acute and cumulative substance exposure on the various brain measures were insignificant. Conclusions: Despite brain changes associated with normative development and potential substance exposure related to EXT symptomatology, both time-domain and time-frequency measures associated with P3 activity continue to provide effective, stable and predictive brain markers related to a wide spectrum of EXT psychopathology. These findings offer further support for the notion that P3-related measures constitute endophenotypes that tap into a neural substrate underlying behavioral disinhibition.

Previous research has indicated the important role of visual information in the speech perception process. These studies have elucidated the areas of the brain involved in the processing of audiovisual stimuli. The McGurk effect, an audiovisual illusion, has been demonstrated to be a useful tool in the study of audiovisual integration. Brain imaging research suggests that the McGurk effect is modulated by brain structures in the Superior Temporal Gyrus, Supplemental Temporal Cortex and Broadman area 41. Electrophysiological studies suggest that the McGurk effect generates a different brainwave than the standard audiovisual congruent condition in frontal, central and parietal regions among N1, P2, N300 and later ERP components. The magnitude of the McGurk effect is influenced by lexical information, cultural difference and language experience, although these effects have not been investigated by electrophysiological methods. The current study compares three experimental groups, native Chinese speakers who had less than three years of residency in the United States; native Chinese speakers with more than three years of residency in the United States; and native English speakers. A high density (256 channels) hydrocel system was used to collect the ERP data from the participants in three experiments. The main effect of McGurk was studied in Experiment 1, by dubbing an audio /ba/ onto a video /ga/. The behavioral responses and the characteristic brainwave of the McGurk effect were examined. The semantic and culturally related McGurk effects were investigated in Experiment 2 and 3. The three groups were contrasted in each of the experiments. The results showed brainwave differences for the McGurk and the standard audiovisual congruent condition in the left hemisphere. These results also revealed a word/nonword separation in the McGurk effect, which provides electrophysiological evidence for an interaction of the McGurk condition and semantic/cognitive processing. Contrary to hypothesis, significant group differences were not found between the two Chinese groups. Limitations and implications of this study are discussed.

Over 800 athletes suffer from concussion in the United States each day, resulting in over 300,000 concussions each year. Recent data has revealed that the incidence of mild traumatic brain injury is on the rise for many different sports, placing athletes at higher risk. Damage is caused by the shearing of axons, which results in swelling and loss of limited function. Electrophysiologic techniques, specifically event-related potentials are one of the most frequently used cognitive assessments. Event-related potentials are a non-invasive method to gather a baseline of cognitive processes and to evaluate cognitive deficits. The current study investigated the sensitivity of event-related potentials in the identification of cognitive deficits following concussion in college athletes. Neuropsychological and electrophysiological measures were collected from two groups of participants allocated by injury versus non-injury. Results from the study found important differences between non-concussed and concussed athletes using electrophysiological measures and neuropsychological test measures.

The goal of this research is to develop tools and techniques for studying voluntary control of cortically recorded event related potentials (ERP) in humans. The application of this research is focused on the development of a Direct Brain Interface (DBI) to help persons with severe communication-impairing disabilities. Signal processing techniques for estimating ERP quality are developed and evaluated. A method of estimating the Signal to Noise Ratio (SNR) of ERPs is implemented as the primary tool for measuring quality. The approach developed is shown to be very effective in identifying ERPs useful for the DBI. The quality measurement techniques are the basis of a new on-line, real-time instrument, an ERP Analyzer. The instrument, which was developed as an integral part of this dissertation research, is used to identify high-quality ERPs for further experimentation, such as feedback training. It provides a test bed upon which ERP experiments and different protocols can be conducted. The instrument was tested extensively with pre-recorded human electrocortical signals as well as during experiments with human subjects. The ERP Analyzer also includes the first real-time prototype of the University of Michigan Direct Brain Interface. A protocol was designed and tested to investigate voluntary control of cortically recorded ERPs in human subjects. Visual feedback of ERP quality was used in a first attempt to train subject's to shape or modify their ERPs. The signal processing techniques and ERP Analyzer together were key elements in the design of the protocol. The experimental protocol was used in a study of two subjects and the results are presented as case studies. While the experimental results did not answer the question of whether cortical ERPs can be voluntarily controlled, they demonstrated that such experiments are feasible with the tools and techniques developed. Suggestions are made for improvements to the protocol and it is hoped that these will lead to exciting results in the near future.

The purpose of this study was to examine language organization in the brain by using a series of three tasks concurrent with event-related potentials (ERPs) to investigate both hemispheric differences and interhemispheric reactions. Overall, the findings from this study support a relative rather than absolute hemispheric specialization for language processing. Despite an overall RVF (LH) advantage, both hemispheres were capable of performing the tasks and benefited from semantic priming.