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Dynamic face stimuli are increasingly used in face perception research, as increasing evidence shows they are perceived differently from static photographs. One popular method for creating dynamic faces is the dynamic morph, which can animate the transition between expressions by blending photographs together. Although morphs offer increased experimental control, their unnatural motion differs from the biological facial motion captured in video recordings. This study aimed to compare ratings of emotion intensity and genuineness in video recordings, dynamic morphs, and static photographs of happy, sad, fearful, and angry expressions. We found that video recordings were perceived to have greater emotional intensity than dynamic morphs, and video recordings of happy expressions were perceived as more genuine compared to happy dynamic morphs. Unexpectedly, static photographs and video recordings had similar ratings for genuineness and intensity. Overall, these results suggest that dynamic morphs may not be an appropriate substitute for video recordings, as they may elicit misleading dynamic effects.

While deepfake technology and AI-generated images have generated concerns about their misuse in society, this opinion piece highlights the potential benefits and applications of these technologies in neuroscience research. Deepfakes have been utilised to create realistic, dynamic face stimuli, allowing researchers to isolate and manipulate specific features, expressions, and behaviours for a better understanding of social perception. AI-generated medical and neuroimaging scans have the potential to enhance the training of AI models for automatically detecting rare neurological pathologies, thereby aiding clinicians while also enhancing our understanding of brain structure and function.The authors argue that experimental psychologists and cognitive neuroscientists should stay informed about these emerging tools and embrace their potential to advance the field of visual neuroscience.

Introduction: Atypical visual and social attention has often been associated with clinically diagnosed autism spectrum disorder (ASD), and with the broader autism phenotype. Atypical social attention is of particular research interest given the importance of facial expressions for social communication, with faces tending to attract and hold attention in neurotypical individuals. In autism, this is not necessarily so, where there is debate about the temporal differences in the ability to disengage attention from a face. Method: Thus, we have used eye-tracking to record saccadic latencies as a measure of time to disengage attention from a central task-irrelevant face before orienting to a newly presented peripheral nonsocial target during a gap-overlap task. Neurotypical participants with higher or lower autism-like traits (AT) completed the task that included central stimuli with varied expressions of facial emotion as well as an inverted face. Results: High AT participants demonstrated faster saccadic responses to detect the nonsocial target than low AT participants when disengaging attention from a face. Furthermore, faster saccadic responses were recorded when comparing disengagement from upright to inverted faces in low AT but not in high AT participants. Conclusions: Together, these results extend findings of atypical social attention disengagement in autism and highlight how differences in attention to faces in the broader autism phenotype can lead to apparently superior task performance under certain conditions. Specifically, autism traits were linked to faster attention orienting to a nonsocial target due to the reduced attentional hold of the task irrelevant face stimuli. The absence of an inversion effect in high AT participants also reinforces the suggestion that they process upright or inverted faces similarly, unlike low AT participants for whom inverted faces are thought to be less socially engaging, thus allowing faster disengagement.

Theories about autism spectrum disorder (ASD) have addressed cognitive deficits however few have examined how comorbid diagnoses, including sleep disturbance, anxiety and depression contribute to the underlying deficits. We investigated potential mediations of common ASD comorbidities in the relationship between sub-clinical autism traits and cognitive performance using an international community sample. Cognitive tasks assessed working memory [executive functioning (EF) theory], mental state attribution [theory of mind (ToM)], and global/local visual processing [weak central coherence (WCC) theory]. Structural equation modelling (SEM) demonstrated sleep disturbance and anxiety mediated the relationship of autism traits on measures of EF, but not WCC and ToM. This suggests that treating the symptoms of sleep disturbance and anxiety may lead to improvements in working memory.

Typically developing adults with low and high Autism Spectrum Quotient (AQ) scores made rapid social evaluations of neutral faces when these were primed by briefly presented emotional faces. High AQ participants rated neutral faces as more threatening than low AQ participants, regardless of the prime condition. Both groups rated target neutral faces as more threatening with fearful compared with neutral primes, while neither group demonstrated an effect of happy primes on the ratings of neutral target faces. These results demonstrate subtle anomalies in rapid visual processing of emotional faces across the broader autism spectrum. They suggest that higher autism traits may be associated with a generalized threat bias in rapid social evaluations.

Individuals with autism spectrum disorder (ASD) have often been reported to demonstrate a range of anomalies in visual perceptual function. Rather than reflecting an epiphenomenon to core social communication difficulties in ASD, a visual disturbance in early development could provide a causal mechanism for some aspects of impaired social communication. An overview of key visual pathways and cortical/subcortical regions of the visual system is provided, to aid the reader in appreciating the subsequent discussion of the relationship between visual processing and social communication. We then outline the evidence for visual anomalies in ASD and propose that an impairment in an infant’s ability to quickly orient visual attention and to rapidly code the dynamics of non-verbal social cues—such as eye gaze and facial expression changes—could be critically important in the development of social skills. Faces are a rich source of information about the emotions and mental states of people with whom we engage. Faces are also used to assess trustworthiness and to predict individual responses. Without rapid visual information processing, faces in particular could become confusing and mysterious. We conclude with some suggestions for future research into the visual contributions to social skills in ASD and argue that the speed of visual information processing—driven by the fast magnocellular ‘M’ channel—is a necessary first step for the development of the social skills associated with the understanding of facial communication cues.

Typically developing adults with low and high Autism Spectrum Quotient (AQ) scores made rapid social evaluations of neutral faces when these were primed by briefly presented emotional faces. High AQ participants rated neutral faces as more threatening than low AQ participants, regardless of the prime condition. Both groups rated target neutral faces as more threatening with fearful compared with neutral primes, while neither group demonstrated an effect of happy primes on the ratings of neutral target faces. These results demonstrate subtle anomalies in rapid visual processing of emotional faces across the broader autism spectrum. They suggest that higher autism traits may be associated with a generalized threat bias in rapid social evaluations.

We applied continuous flash suppression (CFS) during an interocular transfer paradigm to evaluate the importance of awareness and the contribution of early versus late visual structures in size recognition. Specifically, we tested if size judgements of a visible target could be influenced by a congruent or incongruent prime presented to the same or different eye. Without CFS, participants categorised a target as “small” or “large” more quickly when it was preceded by a congruent prime – regardless of whether the prime and target were presented to the same or different eye. Interocular transfer enabled us to infer that the observed priming was mediated by late visual areas. In contrast, there was no priming under CFS, which underscores the importance of awareness. We conclude that awareness and late visual structures are important for size perception and that any subconscious processing of the stimulus has minimal effect on size recognition.

We investigated if the subliminal processing of threatening animal (snakes and spiders) and neutral object (cars and houses) stimuli can influence the discrimination of a subsequent visible stimulus. The prime and target pair were either identical, of the same category but with different physical features, or different in category and physical features. In two experiments, participants discriminated the basic level category (e.g. snake vs. spider) of a visible target stimulus that had been preceded by a visible or perceptually invisible prime stimulus. One experiment used visual masking to render prime stimuli perceptually invisible and the other used continuous flash suppression (CFS). Priming effects were demonstrated in both experiments when the prime was visible but not when the prime was rendered perceptually invisible. These findings demonstrate that conscious awareness could be required in the perceptual discrimination of threatening animal and neutral object images at their specific basic level category.

Our understanding of how form, orientation and size are processed within and outside of awareness is limited and requires further investigation. Therefore, we investigated whether or not the visual discrimination of basic object features can be influenced by subliminal processing of stimuli presented beforehand. Visual masking was used to render stimuli perceptually invisible. Three experiments examined if visible and invisible primes could facilitate the subsequent feature discrimination of visible targets. The experiments differed in the kind of perceptual discrimination that participants had to make. Namely, participants were asked to discriminate visual stimuli on the basis of their form, orientation, or size. In all three experiments, we demonstrated reliable priming effects when the primes were visible but not when the primes were made invisible. Our findings underscore the importance of conscious awareness in facilitating the perceptual discrimination of basic object features.

The Maastricht Acute Stress Test (MAST) is designed to be a simple, quick, and non-invasive procedure aimed at activating the human stress system. The MAST has been developed by combining elements from two of the most common experimental paradigms measuring stress, the Trier Social Stress Test (TSST) and the Cold Pressor Test (CPT). The aim of this study was to use the MAST procedure to elicit strong autonomic and subjective stress responses that can be quantified in terms of (systolic and diastolic) blood pressure, pulse rate, and state anxiety ratings. In healthy individuals, the MAST induced a significant elevation of systolic blood pressure (SBP) from baseline for up to 30 minutes post-MAST, while diastolic blood pressure (DBP) dropped to baseline within 10 minutes post-MAST. Interestingly, the presentation of instructions alerting participants to the procedure resulted in significant elevation of both SBP and DBP above baseline. However, BP measurements prior to test initiation were not as high as those measured immediately after the MAST procedure. Pulse rate data showed limited variability across time points. Self-reported state anxiety increased dramatically from baseline to immediately following the MAST procedure. Further, individuals who reported higher levels of depression and stress were more likely to demonstrate larger increases in SBP in response to the MAST. Together these results support the use of the MAST as a useful tool to activate both acute physiological and subjective measures of the stress response in healthy adults lasting up to 30 minutes.

Autism is usually defined by impairments in the social domain but has also been linked to deficient dorsal visual stream processing. However, inconsistent findings make the nature of this relationship unclear and thus, we examined the role of stimulus-driven transient attention, presumably activated by the dorsal stream in autistic tendency. Contrast thresholds for object discrimination were compared between groups with high and low self-rated autistic tendency utilizing the socially based Autism Spectrum Quotient (AQ). Visual stimuli were presented with either abrupt or with ramped contrast onsets/offsets in order to manipulate the demands of transient attention. Larger impairments in performance of abrupt compared with ramped object presentation were established in the high AQ group. Furthermore, self-reported social skills predicted abrupt task performance, suggesting an important visual perception deficiency in autism-related traits. Autism spectrum disorder may be associated with reduced utilization of the dorsal stream to rapidly activate attention prior to ventral stream processing when stimuli are transient.

In recent years, evidence has emerged to suggest abnormal temporal dynamics of attentional processing in stroke patients, especially those presenting with neglect symptoms. However, there has been little profiling of the nature and extent of such temporal anomalies. In addition, many paradigms currently used to measure the time required to deploy visual attention in stroke require a psychomotor response, and may therefore confound performance outcomes. Thus, the aim of this systematic review was to identify and evaluate studies that have employed non-motor psychophysical paradigms to characterize the temporal deployment of visual attention in space. A total of thirteen non-motor psychophysical studies were identified, in which stimulus exposure times were manipulated to measure the time course of attentional deployment. Findings suggest that prolonged attentional deployment thresholds are more likely to occur with lesions within more ventral areas of the fronto-parietal network, irrespective of whether patients presented with neglect. Furthermore, this deficit was greater following right-hemispheric lesions, suggesting a dominant role for the right-hemisphere in facilitating efficient deployment of attention. These findings indicate that area and hemisphere of lesion may serve as putative markers of attentional deployment efficiency. In addition, findings also provide support for using non-motor psychophysical paradigms as a more rigorous approach to measuring and understanding the temporal dynamics of attention.

One aspect of the social communication impairments that characterize autism spectrum disorder (ASD) include reduced use of often subtle non-verbal social cues. People with ASD, and those with self-reported sub-threshold autistic traits, also show impairments in rapid visual processing of stimuli unrelated to social or emotional properties. Hence, this study sought to investigate whether perceptually non-conscious visual processing is related to autistic traits. A neurotypical sample of thirty young adults completed the Subthreshold Autism Trait Questionnaire and a Posner-like attention cueing task. Continuous Flash Suppression (CFS) was employed to render incongruous hierarchical arrow cues perceptually invisible prior to consciously presented targets. This was achieved via a 10 Hz masking stimulus presented to the dominant eye that suppressed information presented to the non-dominant eye. Non-conscious arrows consisted of local arrow elements pointing in one direction, and forming a global arrow shape pointing in the opposite direction. On each trial, the cue provided either a valid or invalid cue for the spatial location of the subsequent target, depending on which level (global or local) received privileged attention. A significant autism-trait group by global cue validity interaction indicated a difference in the extent of non-conscious local/global cueing between groups. Simple effect analyses revealed that whilst participants with lower autistic traits showed a global arrow cueing effect, those with higher autistic traits demonstrated a small local arrow cueing effect. These results suggest that non-conscious processing biases in local/global attention may be related to individual differences in autistic traits.

Controversy still exists over whether there is a magnocellular deficit associated with developmental dyslexia. Here we utilised a magnocellular system-biased phantom contour form discrimination task defined by high temporal frequency contrast reversals to compare contrast sensitivity in a group of children with dyslexia and an age- and nonverbal intelligence-matched control group (9-14 years). Stimuli were either abruptly presented for 4 refresh frames (34 ms), or in two reduced transience conditions had contrast progressively ramped on and off over either 4 frames or 10 frames (86 ms). Children in the dyslexia group showed increased contrast thresholds compared with the control group in all three conditions, and thus strong evidence for a magnocellular deficit. Although the absolute size of the differences in threshold scores between control and dyslexic groups increased dramatically between the abrupt and the 4 and 10 frame ramped onset stimuli, the similar effect size across all tasks, and also the similar range of contrast change at the first frame of stimulus presentation across all tasks between groups suggests that a similar neural mechanism could provide the locus of the apparent magnocellular deficit in children with dyslexia for all tasks tested. These results suggest that threshold discrimination of stimuli with low contrast and high temporal frequencies designed to target the magnocellular system, and has great potential for early screening for children at risk of visually derived reading difficulties.

Reading disability is a relatively common developmental disorder, the aetiology of which is clouded by conflicting theoretical approaches and the heterogeneity of the subtypes found. Recent advances in understanding of the visual system have revived interest in the role of visual processing in the persisting inability to read fluently that characterises dyslexia. A new integrated model of visual processing based on primate single cell and human electrophysiology may provide such a framework, implicating the magnocellular pathway's role in activating and driving attentional mechanisms in higher order cortical regions. In particular, the recent introduction of transcranial magnetic stimulation (TMS) to create 'transient lesions' may provide causal evidence for dorsal stream feedforward/feedback involvement in rapid visual processing tasks. Such organization is argued to be crucial for the development of fluent reading.

Deficits in cortical inhibition (CI) have been implicated in the pathophysiology of schizophrenia, including decreased transcallosal inhibition (TCI). A closely related phenomenon, which has not yet been studied in schizophrenia, is transcallosal facilitation (TCF). TCI and TCF are thought to maintain a complimentary existence, allowing for the performance of tasks such as unilateral voluntary movement. Therefore, deficient TCI may lead to abnormal expression of TCF. This study aims to confirm the presence of TCI deficits in schizophrenia, and to examine TCF. Thirty consenting participants took part in the study (15 with schizophrenia and 15 healthy controls), although not all were able to complete all aspects of the study. TCI and TCF were measured using dual-pulse transcranial magnetic stimulation methodologies. Patients with schizophrenia exhibited significantly less TCI than controls; there was no difference in TCF, however. The lack of significant TCF findings is discussed in light of the methodological limitations, while the theoretical significance of deficient TCI to the pathophysiology of schizophrenia is considered.

Perception of the passage of time is essential for safe planning and navigation of everyday activities. Findings from the literature have demonstrated a gross underestimation of time interval in right-hemisphere damaged neglect patients, but not in non-neglect unilaterally-damaged patients, compared to controls. This study aimed to investigate retrospective estimation of the duration of a target detection task over two occasions, in 30 stroke patients (12 left-side stroke 15 right-side stroke and 3 right-side stroke with neglect) and 10 transient ischemic attack patients, relative to 31 age-matched controls. Performances on visual short-term and working memory tasks were also examined to investigate the associations between timing abilities with residual cognitive functioning. Initial results revealed evidence of perceptual time underestimation, not just in neglect patients, but also in non-neglect unilaterally-damaged stroke patients and transient ischemic attack patients. Three months later, underestimation of time persisted only in left-side stroke and right-side stroke with neglect patients, who also demonstrated reduced short-term and working memory abilities. Findings from this study suggest a predictive role of residual cognitive impairments in determining the prognosis of perceptual timing abnormalities.

Mapping of the underlying neural mechanisms of visuo-spatial working memory (WM) has been shown to consistently elicit activity in right hemisphere dominant fronto-parietal networks. However to date, the bulk of neuroimaging literature has focused largely on the maintenance aspect of visuo-spatial WM, with a scarcity of research into the aspects of WM involving manipulation of information. Thus, this study aimed to compare maintenance-only with maintenance and manipulation of visuo-spatial stimuli (3D cube shapes) utilizing a 1-back task while functional magnetic resonance imaging (fMRI) scans were acquired. Sixteen healthy participants (9 women, M = 23.94 years, SD = 2.49) were required to perform the 1-back task with or without mentally rotating the shapes 90° on a vertical axis. When no rotation was required (maintenance-only condition), a right hemispheric lateralization was revealed across fronto-parietal areas. However, when the task involved maintaining and manipulating the same stimuli through 90° rotation, activation was primarily seen in the bilateral parietal lobe and left fusiform gyrus. The findings confirm that the well-established right lateralized fronto-parietal networks are likely to underlie simple maintenance of visuo-spatial stimuli. The results also suggest that the added demand of manipulation of information maintained online appears to require further neural recruitment of functionally related areas. In particular mental rotation of visuospatial stimuli required bilateral parietal areas, and the left fusiform gyrus potentially to maintain a categorical or object representation. It can be concluded that WM is a complex neural process involving the interaction of an increasingly large network.

Outcomes of a normative and reliability study on the Raven’s Coloured Progressive Matrices (CPM) are reported for a sample of 618 children from Victoria Australia ranging in age from 6.00 to 11.92 years. Percentile ranks are presented for six age levels. Item analysis, internal consistency, and split-half reliabilities are also described. The CPM demonstrated good inter-item consistency and split-half reliability across the age levels. However, item analysis together with the reliability analyses indicated that the number of items in the CPM could be reduced without detriment to the test’s reliability. The psychometric properties of the CPM are discussed and the norms are compared to previously reported data for Australian children.

Background Although the ventral visual stream is understood to be responsible for object recognition, it has been proposed that the dorsal stream may contribute to object recognition by rapidly activating parietal attention mechanisms, prior to ventral stream object processing. Methods To investigate the relative contribution of the dorsal visual stream to object recognition a group of tertiary students were divided into good and poor motion coherence groups and assessed on tasks classically assumed to rely on ventral stream processing. Participants were required to identify simple line drawings in two tasks, one where objects were presented abruptly for 50 ms followed by a white-noise mask, the other where contrast was linearly ramped on and off over 325 ms and replaced with a mask. Results Although both groups only differed in motion coherence performance (a dorsal stream measure), the good motion coherence group showed superior contrast sensitivity for object recognition on the abrupt, but not the ramped presentation tasks. Conclusions We propose that abrupt presentation of objects activated attention mechanisms fed by the dorsal stream, whereas the ramped presentation had reduced transience and thus did not activate dorsal attention mechanisms as well. The results suggest that rapid dorsal stream activation may be required to assist with ventral stream object processing.

Although rapid automatic naming (RAN) speed and short-term auditory memory are widely recognised as good predictors of reading ability in most age groups, the predictive value of short-term memory for visually presented digits for reading and RAN in young typically developing learner readers (mean age 91.5 months) has seldom been investigated. We found that visual digit span is a better predictor of reading ability than auditory digit span in learner readers. A significant correlation has also been found between RAN speed and visual, but not auditory digit span. These results suggests that RAN speed may be a good predictor of a child's future reading ability and eventual fluency because like visual digit span, it is a measure of rate of access to memory for the visual icons and their semantic name and meaning. The results also suggest that auditory memory is not an important factor in young children learning to read.

The stop signal task is used to investigate inhibition of an initiated response. Converging evidence suggests that right inferior prefrontal cortex is involved in this behavior, although other regions in the prefrontal cortex have also been implicated. One technique used to determine the contribution of specific cortical regions to behavior is repetitive transcranial magnetic stimulation (rTMS). In the present study, fourteen subjects performed the stop signal task before and after receiving a train of rTMS to the left and right dorsolateral prefrontal cortex (DLPFC). The effects of rTMS were determined using event-related potential (ERP) measures that have been associated with response inhibition in previous studies. Stimulation of left and right DLPFC did not affect ERP measures of response inhibition. This negative finding is interpreted with caution, but is consistent with a recent study which found that stimulation of the same region had no effect on a behavioral measure of response inhibition.

Although word recognition is a skill commonly expected to rely more on ventral rather than dorsal stream processing, there is some evidence for a magnocellular/dorsal impairment in dyslexia. The early rapid feedforward/feedback loop through the dorsal stream seen in primate has been suggested to allow an initial global analysis, and in human early activation of parietal attention mechanisms for detecting salient stimuli, facilitating more local level detailed ventral stream processing. To test this model in humans, transcranial magnetic stimulation (TMS) was used to probe the role of early visual cortex (V1/V2) and V5/MT+ in single word identification. TMS over V1/V2 between word onset and 36 ms post word onset disrupted accurate word discrimination, with disruption also evident at approximately 99 ms. TMS over V5/MT+ also disrupted accuracy following stimulation at approximately the same time as word onset and again at 130 ms post word onset. Thus, a role for V5/MT+ in accurate single word identification is apparent suggesting rapid triggering of attention to salient exogenous stimuli may be required prior to processing in primary and temporal cortical regions.

We have recently proposed a model of visual processing in which object recognition through the ventral stream into inferotemporal cortex is facilitated by an initial rapid feedforward sweep through the dorsal stream activating parietal and frontal regions prior to subsequent feedback to primary visual cortex (V1). Modulation of inferotemporal cortex also requires feedback from frontal regions, and horizontal connections from the dorsal stream. Aspects of this model, however, have been called into question—in particular the timing advantage of magnocellular over parvocellular arrivals in V1 (the ‘magnocellular advantage’), the link between attention and the magnocellular system, and also the role of MT in smooth pursuit and saccadic eye movements. These criticisms are each rebutted in detail here, and the basis for a model derived from the magnocellular advantage is reaffirmed.

Evidence from human and primate studies suggests that fast visual processing may utilize signals projecting from primary visual cortex (V1) through the dorsal stream, to area V5/MT+ or beyond and subsequently back into V1. This coincides with the arrival of parvocellular signals en route to the ventral pathway and infero-temporal cortex. Such evidence suggests that the dorsal stream region V5/MT+ is activated rapidly through the traditional hierarchical pathway and also via a less-well-established direct signal to V5/MT+ bypassing V1. To test this, 16 healthy humans underwent transcranial magnetic stimulation (TMS) of V1/V2 and V5/MT+ while performing a motion-direction detection task. A three-alternate forced-choice design (left/right motion, stationary) allowed analysis of the quality of errors made, in addition to the more usual performance measures. Transient disruption of V1/V2 and V5/MT+ significantly reduced accuracy when TMS was applied at or near motion onset. Most participants also showed disrupted performance with TMS application over V1/V2 ∼125 ms post motion onset, and significantly reduced accuracy at 158 ms with V5/MT+ stimulation. The two periods of disruption with V1/V2 TMS are suggestive of feedforward/feedback models, although the earlier period of disruption has not been reported in previous TMS studies. Very early activation of V5/MT+, evidenced by diminished accuracy and reduced perception of motion after TMS may be indicative of a thalamic-extrastriate pathway in addition to the traditionally expected later period of processing. A profound disruption of performance prestimulus onset is more likely to reflect disruption of top-down expectancy than disruption of visual processing.

Objectives Various methods of application of repetitive transcranial magnetic stimulation (TMS) have been evaluated for their potential capacity to alter motor cortical excitability. Initial research suggests that the repetitive application of paired TMS pulses (repetitive paired pulse TMS (rppTMS)) may have greater effects on cortical excitability, perhaps through the facilitation of I-wave interaction. We aimed to compare the post-train effects of 15 min trains of rppTMS to investigate the potential therapeutic application of this technique as well as to compare it to a standard high frequency repetitive TMS paradigm. Methods Ten normal subjects received three 15 min sessions of rppTMS, 5 Hz high frequency rTMS and sham TMS in randomised order. rppTMS consisted of a single train of 180 pulse pairs (0.2 Hz, 1.5 ms inter-stimulus interval, supra-threshold intensity) administered over 15 min. The rTMS condition involved 750 pulses provided in 5 s 5 Hz trains with a 25 s inter-train interval at 90% of the RMT. Motor evoked potential size and cortical silent period duration were assessed before and after each session. Results There were no significant changes in cortical excitability produced by any of the stimulation conditions. Five hertz rTMS produced an increase in cortical silent period duration (p = 0.004) which was not affected by rppTMS. Conclusions Fifteen minutes trains of 1.5 ms rppTMS do not substantially increase post train cortical excitability. Repetitive brief trains of 5 Hz rTMS also do not alter excitability but appear to effect cortical inhibition.

Background While there are many psychophysical reports of impaired magnocellular pathway function in developmental dyslexia (DD), few have investigated parietal function, the major projection of this pathway, in good and poor readers closely matched for nonverbal intelligence. In view of new feedforward-feedback theories of visual processing, impaired magnocellular function raises the question of whether all visually-driven functions or only those associated with parietal cortex functions are equally impaired and if so, whether parietal performance is more closely related to general ability levels than reading ability. Methods Reading accuracy and performance on psychophysical tasks purported to selectively activate parietal cortex such as motion sensitivity, attentional tracking, and spatial localization was compared in 17 children with DD, 16 younger reading-age matched (RA) control children, and 46 good readers of similar chronological-age (CA) divided into CA-HighIQ and a CA-LowIQ matched to DD group nonverbal IQ. Results In the age-matched groups no significant differences were found between DD and CA controls on any of the tasks relating to parietal function, although performance of the DD group and their nonverbal IQ scores was always lower. As expected, CA and RA group comparisons indicated purported parietal functioning improves with age. No difference in performance was seen on any of the parietally driven tasks between the DD and age-nonverbal IQ matched groups, whereas performance differentiated the DD group from the age-matched, higher nonverbal IQ group on several such tasks. An unexpected statistical difference in performance between lower reading age (DD and RA children) and all higher reading age (CA) children was seen on a test of chromatic sensitivity, whereas when high and low nonverbal IQ normal readers were compared performance was not different Conclusion The results indicate that performance on purported parietal functions improves with age and may be more associated with nonverbal mentation than reading accuracy. Performance on a cognitively demanding task, traditionally considered to rely on ventral stream functions, was more related to reading accuracy.

Evidence exists implicating abnormal visual information processing and visually driven attention in a number of neurodevelopmental and psychiatric disorders, suggesting that research into such disorders may benefit from a better understanding of more recent advances in visual system processing. A new integrated model of visual processing based on primate single cell and human electrophysiology may provide a framework, to understand how the visual system is involved, by implicating the magnocellular pathway's role in driving attentional mechanisms in higher-order cortical regions, what we term the 'magnocellular advantage'. Evidence is also presented demonstrating visual processing occurs considerably faster than previously assumed, and emphasising the importance of top-down feedback signals into primary visual cortex, as well as considering the possibility of lateral connections from dorsal to ventral visual areas. Such organisation is argued to be important for future research highlighting visual aspects of impairment in disorders as diverse as schizophrenia and autism.