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Previous behavioural and neuroimaging studies have consistently reported that memory is enhanced for associations congruent or incongruent with the structure of prior knowledge, termed as schemas. However, it remains unclear if similar effects arise with emotion-related associations, and whether they depend on the type of emotions. Here, we addressed this question using a novel face-word pair association paradigm combined with fMRI and eye-tracking techniques. In two independent studies, we demonstrated and replicated that both congruency with emotion schemas and emotion category interact to affect associative memory. Overall, memory retrieval was higher for faces from pairs congruent vs. incongruent with emotion schemas, paralleled by a greater recruitment of left inferior frontal gyrus (IFG) during successful encoding. However, emotion schema effects differed across two negative emotion categories. Disgust was remembered better than fear, and only disgust activated left IFG stronger during encoding of congruent vs. incongruent pairs, suggestive of deeper semantic processing for the associations. On the contrary, encoding of congruent fear vs. disgust-related pairs was accompanied with greater activity in right fusiform gyrus (FG), suggesting a stronger sensory processing of faces. In addition, successful memory formation for congruent disgust pairs was associated with a higher pupil dilation index related to sympathetic activation, longer gaze time on words compared to faces, and more gaze switches between paired words and faces. This was reversed for fear-related congruent pairs where the faces attracted longer gaze time (compared to words). Overall, our results provide converging evidence from behavioural, physiological, and neural measures to suggest that congruency with available emotion schemas influence memory associations in a similar manner to semantic schemas. However, these effects vary across distinct emotion categories, pointing to a differential role of semantic processing and visual attention processes in the modulation of memory by disgust and fear, respectively.

Understanding the neural correlates of repetitive retrieval of emotional events is critical in addressing pathological emotional processing, as repeated processing is central for a number of different therapeutic interventions. In the current study, single-trial functional brain activity was assessed in key regions implicated in episodic retrieval, including the medial prefrontal cortex (mPFC), anterior hippocampus, posterior hippocampus, and the posteromedial parietal cortex (i.e., posterior cingulate cortex and the precuneus) following repeated retrieval of pleasant and unpleasant autobiographical events. Replicating previous studies, repetition prompted reduced blood-oxygen-level-dependent (BOLD) amplitude in the anterior hippocampus and the mPFC, but not in the posterior hippocampus, due to no functional activity during mental imagery, or in the posteromedial parietal cortex, due to enhanced activation that was sustained across repetitions. Neural activation during pleasant and unpleasant autobiographical retrieval did not differ as a function of repetition, indicating similar processing effects regardless of motivational relevance. Taken together, the hedonic valence of retrieved memories does not affect functional activity associated with repeated retrieval of episodic events, in which the pattern of BOLD amplitude change suggests a dissociation between the hippocampal-prefrontal circuit, which shows repetition suppression, and the posteromedial parietal cortex, which shows sustained activation.

Previous studies revealed a close relationship between retrieval ability and creative thinking; however, it is still unclear what processes of creative thinking are influenced by retrieval ability. This study applied a novel task paradigm to distinguish between different processes of creative thinking. We used functional near-infrared spectroscopy (fNIRS) to explore the differences of cortical activation and functional connectivity in the prefrontal cortex (PFC), temporoparietal junction (TPJ) and temporal cortex between high (HRA) and low (LRA) retrieval ability groups during creating original ideas (CO) and recalling original ideas (RO) tasks. The behaviour results revealed that in the CO task, the HRA group performed better than the LRA group on fluency, flexibility, and originality. Importantly, the fNIRS results further indicated that the HRA group exhibited higher activation of the l-TPJ, l-STG, l-MTG, r-FPC, r-DLPFC than the LRA group during the CO task. Moreover, the HRA group exhibited higher activation of the bilateral TPJ, l-STG, l-MTG, r-DLPFC, and r-FPC in the CO task than in the RO task, and the LRA group exhibited higher activation of the l-STG in the CO task than in the RO task. The functional connectivity between the PFC and IFG, TPJ, and MTG of the HRA group was significantly stronger than that of the LRA group in both the CO and RO tasks. The findings suggest that high retrieval ability could facilitate the generation of creative ideas by facilitating the retrieval of novel information and suppression of common information compared to low retrieval ability. This study provides neural evidence for the effect of different levels of retrieval ability on creative thinking.

The ability to control unwanted memories is essential for emotional regulation and maintaining mental health. Previous evidence indicates that suppressing retrieval, which recruits executive control mechanisms to prevent unwanted memories entering consciousness, can cause forgetting, termed suppression-induced forgetting (SIF). Since these executive mechanisms involve multiple mental operations, we hypothesize that the efficacy of SIF may be limited by individuals' capacity limitation of cognitive control. Here, we tested this hypothesis. Participants were assigned to two groups based on the median of their cognitive control capacity (CCC, estimated by the backward masking majority function task) and performed the think/no-think task with electrophysiological signals recorded. The results showed that the SIF effect was observed only in the high CCC group but not in the low CCC group. In accordance, repeated suppression attempts also resulted in a steeper reduction in intrusive thoughts in the high CCC group. Furthermore, ERP analysis revealed a decrease in recollection-related late parietal positivity (LPP) under the no-think condition in the high CCC group. A mediation analysis revealed that the reduced intrusive memories mediated the effect of CCC on SIF. These findings suggest that suppressing retrieval could reduce traces of the unwanted memories, making them less intrusive and harder to recall. More importantly, successful SIF is constrained by the capacity of cognitive control which may be used to ensure the coordination of multiple cognitive processes during suppression.

Distinct brain systems are thought to support statistical learning over different timescales. Regularities encountered during online perceptual experience can be acquired rapidly by the hippocampus. Further processing during offline consolidation can establish these regularities gradually in cortical regions, including the medial prefrontal cortex (mPFC). These mechanisms of statistical learning may be critical during spatial navigation, for which knowledge of the structure of an environment can facilitate future behavior. Rapid acquisition and prolonged retention of regularities have been investigated in isolation, but how they interact in the context of spatial navigation is unknown. We had the rare opportunity to study the brain systems underlying both rapid and gradual timescales of statistical learning using intracranial electroencephalography (iEEG) longitudinally in the same patient over a period of three weeks. As hypothesized, spatial patterns were represented in the hippocampus but not mPFC for up to one week after statistical learning and then represented in the mPFC but not hippocampus two and three weeks after statistical learning. Taken together, these findings clarify that the hippocampus may do the initial work of extracting regularities and transfer these integrated memories to cortex, rather than only storing individual experiences and leaving it up to cortex to extract regularities.HighlightsCase study of an epilepsy patient tested longitudinally over three weeks.We tracked time-dependent changes in neural representations of spatial patterns.Representations reconstructed from hippocampal activity reflected patterns learned within a week.Representations reconstructed from activity in the mPFC reflected patterns learned 2–3 weeks ago.

Spatial navigation and spatial memory are two important skills for independent living, and are known to be compromised with age. Here, we investigate the neural correlates of successful spatial memory in healthy older adults in order to learn more about the neural underpinnings of maintenance of navigation skill into old age. Healthy older adults watched a video shot by a person navigating a route and were asked to remember objects along the route and then attempted to remember object locations by virtually pointing to the location of hidden objects from several locations along the route. Brain activity during watching and pointing was recorded with functional MRI. Larger activations in temporal and frontal regions during watching, and larger deactivations in superior parietal cortex and intraparietal sulcus during pointing, were associated with smaller location errors. These findings suggest that larger evoked responses during learning of spatial information coupled with larger deactivation of canonical spatial memory regions at retrieval are important for effective spatial memory in late life.

Autobiographical memory dysfunction is a pervasive feature of neurodegenerative disorders, but less is known about the integrity of autobiographical memory in Huntington's disease (HD). Deficits in anterograde verbal episodic memory on traditional neuropsychological tests have been detected in HD, however, whether personally-relevant autobiographical retrieval is also affected is unknown. We examined autobiographical memory performance in 26 participants genetically confirmed to have HD who were in the peri-manifest stage of the disease (including 12 in the late premanifest stage and 14 who were early diagnosed), and 24 matched controls using the Autobiographical Interview (AI), a semi-structured interview assessing retrieval of autobiographical details from discrete epochs across the lifetime. Relative to controls, people with HD exhibited global episodic autobiographical memory impairments, regardless of recency or remoteness of the memory being retrieved. While specific cues bolstered the retrieval of episodic (internal) details in HD participants, their performance remained significantly below that of controls. Moreover, following probing, people with HD retrieved more extraneous (external) details not directly related to the autobiographical event they originally retrieved, including semantic details, repetitions, and metacognitive statements. Our results reveal marked autobiographical memory dysfunction in HD, not directly attributable to strategic retrieval deficits, and suggest that autobiographical memory impairment may represent an overlooked feature of the cognitive phenotype of HD.

Our everyday memories can vary in terms of accuracy and phenomenology. According to one theoretical account, these differences hinge on whether the memories contain information about both an item itself as well as associated details (remember) versus those that are devoid of these associated contextual details (familiar). This distinction has been supported by computational modeling of behavior, studies in patients, and neuroimaging work including differences both in electrophysiological and functional magnetic resonance imaging. At present, however, little evidence has emerged to suggest that neurophysiological measures track individual differences in estimates of recollection and familiarity. Here, we conducted electrophysiological recordings of brain activity during a recognition memory task designed to differentiate between behavioral indices of recollection and familiarity. Non-parametric cluster-based permutation analyses revealed associations between electrophysiological signatures of familiarity and recollection with their respective behavioral estimates. These results support the idea that recollection and familiarity are distinct phenomena and is the first, to our knowledge, to identify distinct electrophysiological signatures that track individual differences in these processes.

Face recognition abilities, which play a critical role in social interactions, involve face processing and identifying familiar faces, but also remembering one-off encounters with previously unfamiliar faces. Previous functional imaging and lesion studies have found evidence for temporal, frontal, and parietal contributions to episodic recognition memory for previously unfamiliar faces. However, the functional contributions of these regions remain unclear. We, therefore, conducted a systematic group analysis of this memory function using lesion-behavior mapping. 95 first-event stroke patients (53 with right- and 42 with left-hemisphere damage) in the sub-acute phase performed the Wechsler Memory Scale (WMS-III) face recognition memory subtest. We analyzed their performance relative to 75 healthy controls, using signal detection measures. To identify brain lesions specifically implicated in face recognition deficits, we used voxel-based lesion-behavior mapping (VLBM; an analysis comparing the performance of participants with and without damage affecting a given voxel). Behavioral analysis disclosed a pronounced impairment in the performance of patients with right hemisphere damage. Frontal damage was associated with an increased amount of false alarms (i.e., failed rejection of new face items) and overly liberal criterion setting, without affecting the recognition of studied faces. In contrast, parietal damage was associated with impaired recognition of studied faces, which was more pronounced in immediate than in delayed retrieval. These findings suggest the existence of multifactorial neurocognitive processes in recognition memory for unfamiliar faces.

Scene imagery features prominently when we recall autobiographical memories, imagine the future and navigate around in the world. Consequently, in this study we sought to better understand how scene representations are supported by the brain. Processing scenes involves a variety of cognitive processes that in the real world are highly interactive. Here, however, our goal was to separate semantic and spatial constructive scene processes in order to identify the brain areas that were distinct to each process, those they had in common, and the connectivity between regions. To this end, participants searched for either semantic or spatial constructive impossibilities in scenes during functional MRI. We focussed our analyses on only those scenes that were possible, thus removing any error detection that would evoke reactions such as surprise or novelty. Importantly, we also counterbalanced possible scenes across participants, enabling us to examine brain activity and connectivity for the same possible scene images under two different conditions. We found that participants adopted different cognitive strategies, which were reflected in distinct oculomotor behaviour, for each condition. These were in turn associated with increased engagement of lateral temporal and parietal cortices for semantic scene processing, the hippocampus for spatial constructive scene processing, and increased activation of the ventromedial prefrontal cortex (vmPFC) that was common to both. Connectivity analyses showed that the vmPFC switched between semantic and spatial constructive brain networks depending on the task at hand. These findings further highlight the well-known semantic functions of lateral temporal areas, while providing additional support for the previously-asserted contribution of the hippocampus to scene construction, and recent suggestions that the vmPFC may play a key role in orchestrating scene processing., Highlights • Semantic and spatial constructive scene processing rely on distinct brain regions. • Temporal cortex supports semantic and hippocampus constructive scene processing. • vmPFC supports both types of scene processing but with different time courses. • vmPFC changes connectivity based on the need for semantic or constructive processes.

Visuo-spatial context and emotional valence are powerful cues to episodic retrieval, but the contribution of these inputs to semantic cognition has not been widely investigated. We examined the impact of visuo-spatial, facial emotion and prosody cues and miscues on the retrieval of dominant and subordinate meanings of ambiguous words. Cue photographs provided relevant visuo-spatial or emotional information, consistent with the interpretation of the ambiguous word being probed, while miscues were consistent with an alternative interpretation. We compared the impact of these cues in healthy controls and semantic aphasia patients with deficient control over semantic retrieval following left-hemisphere stroke. Patients showed greater deficits in retrieving the subordinate meanings of ambiguous words, and stronger effects of cueing and miscuing relative to healthy controls. These findings suggest that contextual cues that guide retrieval to the appropriate semantic information reduce the need to constrain semantic retrieval internally, while miscues that are not aligned with the task increase the need for semantic control. Moreover, both valence and visuo-spatial context can prime particular semantic interpretations, in line with theoretical frameworks that argue meaning is computed through the integration of these features. In semantic aphasia, residual comprehension relies heavily on facial expressions and visuospatial cues. This has important implications for patients, their families and clinicians when developing new or more effective modes of communication.

The present study used event-related potentials (ERPs) to investigate the contribution of perceptual fluency to recognition memory in different fluency contexts. In a recognition memory test with a modified remember-know paradigm, we employed conceptually impoverished items (kaleidoscope images) as stimuli and manipulated the perceptual fluency of recognition test cues through masked repetition priming. There were two fluency context conditions. In the random fluency context (RC) condition, primed and unprimed trials were randomly inter-mixed. In the blocked fluency context (BC) condition, primed and unprimed trials were grouped into blocks. Behavioral results showed that priming elevated the incidence of remember hits and the accuracy of remember judgements in the RC condition; no such effects were evident in the BC condition. In addition, priming effects on reaction times were found only for remember hit responses in the RC condition. The ERP results revealed an early100-200 ms effect related to masked repetition priming, which took the form of greater positivity for primed than unprimed trials. This effect was modulated neither by fluency context or response type. The present findings suggest that perceptual fluency induced by masked repetition priming affects recollection-related memory judgments in a specific fluency context and indicate that relative, rather absolute, fluency plays a critical role in influencing recognition memory judgments.

The Autobiographical Interview (AI) separates internal (episodic) and external (non-episodic) details from transcribed protocols using an exhaustive and reliable scoring system. While the details comprising the internal composite are centered on elements of episodic memory, external details are more heterogeneous as they are meant to capture a variety of non-episodic utterances: general semantics, different types of personal semantics details, metacognitive statements, repetitions, and details about off topic events. Elevated external details are consistently observed in aging and in neurodegenerative diseases. In the present study, we augmented the AI scoring system to differentiate subtypes of external details to test whether the elevation of these details in aging and frontotemporal lobar degeneration (including mixed frontotemporal/semantic dementia [FTD/SD] and progressive non-fluent aphasia [PNFA]) would be specific to general and personal semantics or would concern all subtypes. Specifically, we separated general semantic details from personal semantic details (including autobiographical facts, self-knowledge, and repeated events). With aging, external detail elevation was observed for general and personal semantic details but not for other types of external details. In frontotemporal lobar degeneration, patients with FTD/SD (but not PNFA) generated an excess of personal semantic details ¬but not general semantic details. The increase in personal but not general semantic details in FTD/SD is consistent with prevalent impairment of general semantic memory in SD, and with the personalization of concepts in this condition. Under standard AI instructions, external details were intended to capture off-topic utterances and were not intended as a direct measure of semantic abilities. Future investigations concerned with semantic processing in aging and in dementia could modify standard instructions of the AI to directly probe semantic content.

Successful episodic recollection can vary in the precision of the information recalled. The hypothesis that recollection precision requires functional neuroanatomical contributions distinct from those required for recollection success remains controversial. Some findings in individuals with hippocampal lesions have indicated that precision is dependent on the hippocampus. However, other neuroimaging and lesion studies have implicated regions outside of the mesial temporal lobe (MTL) in precision, such as parietal cortex. To further elucidate distinctions of recollection precision versus success, we examined whether they were differentially sensitive to aging and to unilateral MTL lesions. Precision and success were measured using a novel task that required memory for item-location associations across different spatial contexts. We found impairments in recollection precision, but not success, in older adults (59-80 years) relative to younger adults (18-33 years). Recollection precision was also selectively impaired in individuals with unilateral MTL resections made to treat refractory epilepsy. Moreover, recollection precision was significantly worse when resections included the hippocampus compared to when only non-hippocampal MTL tissue was resected. These findings suggest that the MTL is critically involved in the high-resolution binding required to support spatial recollection precision, and thus provide evidence for functional neuroanatomical differences between recollection success and precision.

Theoretical explanations of the testing effect (why people learn better from a test than a re-study) have largely focused on either the benefit of attempting to retrieve the answer or on the benefit of re-encoding the queried information after a successful retrieval. While a less parsimonious account, prior neuroimaging evidence has led us to postulate that both of these processes contribute to the benefit of testing over re-study. To provide further empirical support for our position, we recorded ERPs while subjects attempted to recall the second word of a pair when cued with the first. These ERPs were analyzed based on the current response accuracy and as a function of accuracy on the subsequent test, yielding three groups: the first and second tests were correct, the first was correct and the second was not, both were incorrect. Mean amplitude waveforms during the first test showed different patterns depending on the outcome patterns: Between 400 and 700 ms the amplitudes were most positive when both tests were correct and least positive when both were incorrect; mean amplitudes between 700 and 1000 ms only differed as a function of subsequent memory. They were more positive when the second test was correct. Importantly, the later component only predicted subsequent memory when the answers were not overlearned, i.e. only correctly recalled once previously. We interpret the 400–700 ms time window as a component reflecting a retrieval attempt process, which differs as a function of both current and subsequent accuracy, and the later time window as a component reflecting a re-encoding process, which only involves learning from tests, both of which are involved in the testing effect.

Flashbulb memories (FM) are a subgroup of autobiographical memories referring to the circumstances in which a person first heard of a surprising, emotionally arousing event. Patients with temporal lobe epilepsy (TLE) have been reported to be impaired in FM recall. As emotional arousal is central to FM, various authors have suggested a crucial role of the amygdala. However, to date, no studies have directly addressed this hypothesis. In this study, 33 TLE patients and 20 healthy controls (HC) were tested on an FM task twice with a minimum interval of two months. FM recall quality was measured as consistency of the answers. Patients were grouped according to the presence as well as the lateralisation of amygdalar damage, using information of brain imaging and intracranial electroencephalography-recordings. Analyses revealed that, relative to HC, patients with amygdalar damage had significantly diminished FM recall quality, whereas patients with intact amygdalae did not. Particularly patients with amygdalar damage in the non-language-dominant hemisphere performed significantly worse than HC. Findings suggest a negative influence of amygdalar damage, possibly especially in the non-dominant hemisphere, on FM retrieval quality. Given the shocking character of events evoking FM, a rapid emotion detection system involving the right (i.e. non-dominant) amygdala could be influential to FM formation. Thus, the present findings support previous, not yet examined, hypotheses concerning a crucial role of the amygdala in FM.

Retrieval of autobiographical memories entails periods of search, access, and elaboration. Women's reports of their memories feature more detail and emotional content relative to men's. A key question is how these gender differences relate to unfolding changes in cortical activity during retrieval. We recorded EEG activity from 32 scalp electrodes as women and men were cued to retrieve positive, negative, and neutral autobiographical memories. Alpha (9-12Hz) oscillations were prominent at all EEG channels. Alpha coherence between channels was calculated as a measure of ms-level cortical synchrony. Across participants and memory types, a frontal cluster showed pronounced decreases in coherence with other channels during the first second of autobiographical retrieval. In the following second, a left parietal-centered cluster showed increased coherence with other channels. This effect strengthened and spread in the third second of retrieval, perhaps reflecting trace elaboration and/or evaluation of the memory. Although women and men gave similar subjective ratings of their memories, the second-by-second pattern of alpha coherence during autobiographical retrieval differed by gender and memory type. Specifically, women sustained the increased pattern of left-parietal coherence throughout the trial, whereas for men, alpha coherence in this cluster returned to baseline by second two for neutral memories and by second three for emotional memories. Examination of the temporal dynamics of cortical oscillations provides novel insight into autobiographical memory retrieval processes and to gendered retrieval in particular, suggesting that women may persist with elaboration and/or evaluation to a greater extent than men.

Although autobiographical memory and episodic simulations recruit similar core brain regions, episodic simulations engage additional neural recruitment in the frontoparietal control network due to greater demands on constructive processes. However, previous functional neuroimaging studies showing differences in remembering and episodic simulation have focused on veridical retrieval of past experiences, and thus have not fully considered how retrieving the past in different ways from how it was originally experienced may also place similar demands on constructive processes. Here we examined how alternative versions of the past are constructed when adopting different egocentric perspectives during autobiographical memory retrieval compared to simulating hypothetical events from the personal past that could have occurred, or episodic counterfactual thinking. Participants were asked to generate titles for specific autobiographical memories from the last five years, and then, during functional magnetic resonance (fMRI) scanning, were asked to repeatedly retrieve autobiographical memories or imagine counterfactual events cued by the titles. We used an fMRI adaptation paradigm in order to isolate neural regions that were sensitive to adopting alternative egocentric perspectives and counterfactual simulations of the personal past. The fMRI results revealed that voxels within left posterior inferior parietal and ventrolateral frontal cortices were sensitive to novel visual perspectives and counterfactual simulations. Our findings suggest that the neural regions supporting remembering become more similar to those underlying episodic simulation when we adopt alternative egocentric perspectives of the veridical past.

The subjective sense of recollecting events from one's past is an essential feature of episodic memory, but the neural mechanisms supporting this capacity are poorly understood. We examined the role of large-scale patterns of neural synchrony using whole-head MEG recordings in healthy adults and S.M., who has severely deficient autobiographical memory (SDAM; Palombo et al., 2015), a syndrome in which autobiographical recollection is absent but other functions (including other mnemonic functions), are normal. MEG was conducted while participants listened to prospectively collected recordings documenting unique personal episodes (PE) that normally evoke rich recollection, as well as a condition including general semantic information that is non-specific in place or time (GS; Levine et al., 2004). We predicted that PE (and not GS) would be associated with changes in patterns of large-scale neural synchrony in comparison subjects. We found large-scale neural synchrony, specifically in the gamma frequency ranges (i.e., 27–45 Hz), specific to PE and not GS. These synchrony differences between PE and GS were not apparent in S.M. Our findings provide empirical evidence for the supporting role of large-scale gamma neural synchrony underlying autobiographical recollection.

The ability to categorize objects and events is a fundamental human skill that depends upon the representation of multimodal conceptual knowledge. This study investigated the acquisition and consolidation of categorical information that required participants to integrate information across visual and auditory dimensions. The impact of wake- and sleep-dependent consolidation was investigated using a paradigm in which training and testing were separated by a delay spanning either an evening of sleep or daytime wakefulness, with a paired-associate episodic memory task used as a measure of classic sleep-dependent consolidation. Participants displayed good evidence of category learning, but did not show any wake- or sleep-dependent changes in memory for category information immediately following the delay. This is in contrast to paired-associate learning, where a sleep-dependent benefit was observed in memory recall. To replicate real-world concept learning, in which knowledge is acquired across multiple distinct episodes, participants were given a second opportunity for category learning following the consolidation delay. Here we found an interaction between consolidation and learning; with greater improvements in category knowledge as a result of the second learning session for those participants who had a sleep-filled delay. These results suggest a role for sleep in the consolidation of recently acquired categorical knowledge; however this benefit does not emerge as an immediate benefit in memory recall, but by enhancing the effectiveness of future learning. This study therefore provides insights into the processes responsible for the formation and development of conceptual representations., Highlights • Investigation into sleep- and wake-associated consolidation on declarative memory and cross-modal category learning. • Declarative memory showed immediate sleep-associated improvements. • Category knowledge remained stable across all consolidation delays, with no sleep-associated changes in performance. • Sleep-associated consolidation did however increase the effectiveness of post-delay category learning.

Healthy aging is accompanied by increased false remembering in addition to reduced successful remembering in older adults. Neuroimaging studies implicate age-related differences in the involvement of medial temporal lobe and fronto-parietal regions in mediating highly confident false recollection. However, no studies have directly examined the relationship between white matter microstructure and false recollection in younger and older adults. Using diffusion-weighted imaging and probabilistic tractography, we examined how white matter microstructure within tracts connecting the hippocampus and the fronto-parietal retrieval network contribute to false recollection rates in healthy younger and older adults. We found only white matter microstructure within the fornix contributed to false recollection rates, and this relationship was specific to older adults. Fornix white matter microstructure did not contribute to true recollection rate, nor did common white matter contribute to false recollection, suggesting fornix microstructure is explicitly associated with highly confident false memories in our sample of older adults. These findings underlie the importance of examining microstructural correlates associated with false recollection in younger and older adults.

Prior work demonstrates that application of transcranial direct current stimulation (tDCS) improves memory. In this study, we investigated tDCS effects on face-name associative memory using both recall and recognition tests. Participants encoded face-name pairs under either active (1.5mA) or sham (.1mA) stimulation applied to the scalp adjacent to the left dorsolateral prefrontal cortex (dlPFC), an area known to support associative memory. Participants' memory was then tested after study (day one) and then again after a 24-h delay (day two), to assess both immediate and delayed stimulation effects on memory. Results indicated that active relative to sham stimulation led to substantially improved recall (more than 50%) at both day one and day two. Recognition memory performance did not differ between stimulation groups at either time point. These results suggest that stimulation at encoding improves memory performance by enhancing memory for details that enable a rich recollective experience, but that these improvements are evident only under some testing conditions, especially those that rely on recollection. Overall, stimulation of the dlPFC could have led to recall improvement through enhanced encoding from stimulation or from carryover effects of stimulation that influenced retrieval processes, or both.

During neurorehabilitation, the re-learning of motor sequences is crucial for patients with motor deficits, enabling them to master again complex movements. A recent study showed that patients with left hemisphere (LH) stroke exhibited preserved motor sequence learning (as assessed by the serial reaction time (SRT) task) when the timing of the stimuli was comparable in the training and later test phase. However, patients showed significantly smaller learning scores as compared to healthy controls when the temporal delay between the patient's motor response and the following stimulus was randomized in the test phase. We here investigated whether LH stroke patients were able to learn spatial motor sequences even if no predictable temporal information was provided (i.e., adopting random response-stimulus intervals, RSIs) already during the training phase. Twelve right-handed LH stroke patients and 18 right-handed healthy controls performed a SRT task with random RSIs to test incidental learning of a complex spatial motor sequence. Results indicate that, although the learning condition with random RSIs was more difficult than learning with predictable RSIs, LH stroke patients performed as well as healthy controls regarding sequence specific learning. Thus, data show for the first time that LH stroke patients are able to incidentally learn a spatial sequence even when no predictable temporal information is available.

The organization of semantic information in the brain has been mainly explored through category-based models, on the assumption that categories broadly reflect the organization of conceptual knowledge. However, the analysis of concepts as individual entities, rather than as items belonging to distinct superordinate categories, may represent a significant advancement in the comprehension of how conceptual knowledge is encoded in the human brain. Here, we studied the individual representation of thirty concrete nouns from six different categories, across different sensory modalities (i.e., auditory and visual) and groups (i.e., sighted and congenitally blind individuals) in a core hub of the semantic network, the left angular gyrus, and in its neighboring regions within the lateral parietal cortex. Four models based on either perceptual or semantic features at different levels of complexity (i.e., low- or high-level) were used to predict fMRI brain activity using representational similarity encoding analysis. When controlling for the superordinate component, high-level models based on semantic and shape information led to significant encoding accuracies in the intraparietal sulcus only. This region is involved in feature binding and combination of concepts across multiple sensory modalities, suggesting its role in high-level representation of conceptual knowledge. Moreover, when the information regarding superordinate categories is retained, a large extent of parietal cortex is engaged. This result indicates the need to control for the coarse-level categorial organization when performing studies on higher-level processes related to the retrieval of semantic information.

Aging effects on regional brain activation have been studied extensively to explain the gradual recollection failure that occurs with advancing age. However, little is known about the consequence of aging on the interaction among brain regions that support recollection. The purpose of this study was to examine effective connectivity at encoding and retrieval during successful and unsuccessful recollection in young and old adults. In particular, we analyzed a recollection network that is characterized by its susceptibility to aging effects by middle age or later, which is comprised of the occipital cortex, hippocampus and orbitofrontal cortex. Participants' brains were scanned using functional magnetic resonance imaging while they performed a spatial source memory task. Dynamic causal modeling and Bayesian model selection revealed that subsequent recollection during encoding and recollection during retrieval modulated the influence of the orbitofrontal cortex on the hippocampus in both age groups; this particular connectivity was not modulated by unsuccessful encoding in either group. Successful encoding and retrieval of item-source associations modulated all connections within the network in old adults. The findings revealed that the orbitofrontal cortex influences processes in the hippocampus to ensure successful recollection, and aging alters the recollection network by engaging non-specialized connections.

Understanding the neural processes that underlie learning to read can provide a scientific foundation for literacy education but studying these processes in real-world contexts remains challenging. We present behavioural data from adult participants learning to read artificial words and name artificial objects over two days. Learning profiles and generalisation confirmed that componential learning of visual-verbal associations distinguishes reading from object naming. Functional MRI data collected on the second day allowed us to identify the neural systems that support componential reading as distinct from systems supporting holistic visual-verbal associations in object naming. Results showed increased activation in posterior ventral occipitotemporal (vOT), parietal, and frontal cortices when reading an artificial orthography compared to naming artificial objects, and the reverse profile in anterior vOT regions. However, activation differences between trained and untrained words were absent, suggesting a lack of cortical representations for whole words. Despite this, hippocampal responses provided some evidence for overnight consolidation of both words and objects learned on day 1. The comparison between neural activity for artificial words and objects showed extensive overlap with systems differentially engaged for real object naming and English word/pseudoword reading in the same participants. These findings therefore provide evidence that artificial learning paradigms offer an alternative method for studying the neural systems supporting language and literacy. Implications for literacy acquisition are discussed., Highlights • Generalisation of novel orthography shows componential processing in reading. • Real and artificial words and objects rely upon the same neural systems. • Different neural systems support reading novel orthography and naming novel objects. • No evidence of whole-word cortical representations for artificial written words. • Reduced hippocampal responses suggest overnight consolidation of artificial items.

Previous research has shown that individuals with Parkinson's disease (PD) show preserved learning of tool-related motor skills, while retention was impaired after a three-week delay, possibly as a result of striatal dysfunction. The goal of the current study was to identify if shorter delays and more extensive practice might reduce retention deficits related to complex tool use in PD. PD participants and healthy age and education-matched controls were trained to use novel tools across four sessions, spaced one-day, one-week, and three-weeks apart. Recall of tool attributes (e.g., function) and skilled motor performance using tools was investigated by examining patterns of learning and forgetting over time. Results showed that tool attribute recall was unimpaired in PD participants relative to controls. For motor skill performance, PD participants were unimpaired in motor skill learning within sessions, but they did not retain these skills across one-week and three-week delays between sessions. This dissociation suggests that the striatum plays a critical role in retention of motor skills needed in skilled tool use performance. Finally, in spite of forgetting, individuals with PD still demonstrated improvement across sessions with additional training, suggesting that people with PD may benefit from extensive practice when learning motor skills.

Receptive language (e.g., reading) is largely preserved in the aging brain, and semantic processes in particular may continue to develop throughout the lifespan. We investigated the neural underpinnings of phonological and semantic retrieval in older and younger adults during receptive language tasks (rhyme and semantic similarity judgments). In particular, we were interested in the role of competition on language retrieval and varied the similarities between a cue, target, and distractor that were hypothesized to affect the mental process of competition. Behaviorally, all participants responded faster and more accurately during the rhyme task compared to the semantic task. Moreover, older adults demonstrated higher response accuracy than younger adults during the semantic task. Although there were no overall age-related differences in the neuroimaging results, an Age × Task interaction was found in left inferior frontal gyrus (IFG), with older adults producing greater activation than younger adults during the semantic condition. These results suggest that at lower levels of task difficulty, older and younger adults engaged similar neural networks that benefited behavioral performance. As task difficulty increased during the semantic task, older adults relied more heavily on largely left hemisphere language regions, as well as regions involved in perception and internal monitoring. Our results are consistent with the stability of language comprehension across the adult lifespan and illustrate how the preservation of semantic representations with aging may influence performance under conditions of increased task difficulty.

Semantic Aphasia (SA) patients have difficulty accessing semantic knowledge in both verbal and non-verbal tasks appropriately for the current context. Automatically activated semantic knowledge overwhelms the system, because it is no longer able to inhibit interference from dominant meanings in order to select weaker alternatives. Episodic memory, like semantic memory, requires control to select relevant memories amongst competing episodes. For example, our memory for what we ate for breakfast last Saturday is affected by competition from numerous other breakfast meals eaten on other days. Where one is unable to guide retrieval, we may rely on automatically activated knowledge about “breakfast foods”, and therefore experience false memories. Brain systems that support semantic control are also implicated in episodic control, and therefore deficits in semantic control are likely to cause more widespread problems. Despite this, nearly all research to date focuses on semantic performance alone. This study explored the impact of this semantic impairment on episodic recall. We used a verbal and non-verbal episodic memory task: participants remembered nursery rhymes in the verbal condition and logos and their associated products in the visual condition (e.g. BOWL OF CEREAL and COCO-POPS). For both tasks, we manipulated a) congruency with pre-existing knowledge (e.g. expectancy of trials: BAA BAA BLACK BUILD – instead of SHEEP) and b) whether these trial types were blocked by congruency or mixed, as well as (c) distractor strength. If SA patients experience overwhelming automatic activation, they should find incongruent items more difficult to suppress, particularly when presented in an unpredictable task format. A total of 13 SA patients were compared to 33 controls across three experiments. In line with our predictions, SA patients found it more difficult to retrieve episodic memories which were in conflict with pre-existing semantic knowledge. This was true across modalities. Moreover, these deficits were accentuated when the congruency was presented in a mixed fashion, and so unpredictable across trials. Evidence of these episodic control impairments in SA cases supports the idea of a shared mechanism for semantic and episodic memory control.

© 2020 We review evidence from an extensive single case study in an individual (NB) who underwent a rare left-sided anterior temporal-lobe resection with sparing of the hippocampus. Our study aimed to determine whether memory functions of perirhinal cortex, which was largely removed in the resection, can be impaired against a background of preserved hippocampus-dependent memory processing. This research was guided by the proposal that item-based familiarity assessment relies on contributions of perirhinal cortex, and that the hippocampus plays a unique role in the relational binding of items to episodic contexts, which is critical for recollection. Seven sets of findings have emerged from our research on NB (synthesized from five primary research articles), and from follow-up work in other patients: (i) Familiarity impairments can be selective and be revealed with multiple methods; (ii) selective familiarity and selective recollection impairments can be double dissociated; (iii) selective familiarity impairments show material specificity; (iv) selective familiarity impairments extend to assessment of cumulative lifetime experience; (v) selective familiarity impairments are sensitive to degree of feature overlap between object concepts; (vi) selective familiarity impairments are associated with preserved task-related fMRI signals in the hippocampus; (vii) selective familiarity impairments can be observed in other lesion cases. Despite our main focus on the dual-process framework, we also discuss implications for the functional organization of the medial temporal lobes in broader terms. We argue that our findings shed light on this organization even if the functional specialization of different medial temporal structures is ultimately not fully captured with reference to the cognitive distinction between familiarity and recollection.