Visual Form-Processing Deficits in Autism

The role of pattern coherence in interocular grouping during binocular rivalry: Insights from individual differences

Interocular grouping during binocular rivalry occurs when two images presented to each eye combine into a coherent pattern. The experience of interocular grouping is thought to be influenced by both eye-of-origin, which involves excitatory lateral connections among monocular neurons, and pattern coherence, which results from top-down intervention from higher visual areas. However, it remains unclear which factor plays a more significant role in the interocularly-grouped percepts during binocular rivalry. The current study employed an individual difference approach to investigate whether grouping dynamics are mainly determined by eye-of-origin or pattern coherence. We found that participants who perceived interocularly-driven coherent percepts for a longer duration also tended to experience longer periods of monocularly-driven coherent percepts. In contrast, participants who experienced non-coherent piecemeal percepts for an extended duration in conventional rivalry also had longer duration of non-coherent percepts in the interocular coherence setting. This individual differences in experiencing interocular grouping suggest that pattern coherence exerts a stronger influence on grouping dynamics during binocular rivalry compared to eye-of-origin factors.

Deficits in Face Recognition and Consequent Quality-of-Life Factors in Individuals with Cerebral Visual Impairment

Individuals with cerebral visual impairment (CVI) frequently report challenges with face recognition, and subsequent difficulties with social interactions. However, there is limited empirical evidence supporting poor face recognition in individuals with CVI and the potential impact on social-emotional quality-of-life factors. Moreover, it is unclear whether any difficulties with face recognition represent a broader ventral stream dysfunction. In this web-based study, data from a face recognition task, a glass pattern detection task, and the Strengths and Difficulties Questionnaire (SDQ) were analyzed from 16 participants with CVI and 25 controls. In addition, participants completed a subset of questions from the CVI Inventory to provide a self-report of potential areas of visual perception that participants found challenging. The results demonstrate a significant impairment in the performance of a face recognition task in participants with CVI compared to controls, which was not observed for the glass pattern task. Specifically, we observed a significant increase in threshold, reduction in the proportion correct, and an increase in response time for the faces, but not for the glass pattern task. Participants with CVI also reported a significant increase in sub-scores of the SDQ for emotional problems and internalizing scores after adjusting for the potential confounding effects of age. Finally, individuals with CVI also reported a greater number of difficulties on items from the CVI Inventory, specifically the five questions and those related to face and object recognition. Together, these results indicate that individuals with CVI may demonstrate significant difficulties with face recognition, which may be linked to quality-of-life factors. This evidence suggests that targeted evaluations of face recognition are warranted in all individuals with CVI, regardless of their age.

Internal noise measures in coarse and fine motion direction discrimination tasks and the correlation with autism traits

Motion perception is essential for visual guidance of behavior and is known to be limited by both internal additive noise (i.e., a constant level of random fluctuations in neural activity independent of the stimulus) and motion pooling (global integration of local motion signals across space). People with autism spectrum disorder (ASD) display abnormalities in motion processing, which have been linked to both elevated noise and abnormal pooling. However, to date, the impact of a third limit-induced internal noise (internal noise that scales up with increases in external stimulus noise)-has not been investigated in motion perception of any group. Here, we describe an extension on the double-pass paradigm to quantify additive noise and induced noise in a motion paradigm. We also introduce a new way to experimentally estimate motion pooling. We measured the impact of induced noise on direction discrimination, which we ascribe to fluctuations in decision-related variables. Our results are suggestive of higher internal noise in individuals with high ASD traits only on coarse but not fine motion direction discrimination tasks. However, we report no significant correlations between autism traits and additive noise, induced noise, or motion pooling in either task. We conclude that, under some conditions, the internal noise may be higher in individuals with pronounced ASD traits and that the assessment of induced internal noise is a useful way of exploring decision-related limits on motion perception, irrespective of ASD traits.

How the External Visual Noise Affects Motion Direction Discrimination in Autism Spectrum Disorder

Along with social, cognitive, and behavior deficiencies, peculiarities in sensory processing, including an atypical global motion processing, have been reported in Autism Spectrum Disorder (ASD). The question about the enhanced motion pooling in ASD is still debatable. The aim of the present study was to compare global motion integration in ASD using a low-density display and the equivalent noise (EN) approach. Fifty-seven children and adolescents with ASD or with typical development (TD) had to determine the average direction of movement of 30 Laplacian-of-Gaussian micro-patterns. They moved in directions determined by a normal distribution with a standard deviation of 2°, 5°, 10°, 15°, 25°, and 35°, corresponding to the added external noise. The data obtained showed that the ASD group has much larger individual differences in motion direction thresholds on external noise effect than the TD group. Applying the equivalent noise paradigm, we found that the global motion direction discrimination thresholds were more elevated in ASD than in controls at all noise levels. These results suggest that ASD individuals have a poor ability to integrate the local motion information in low-density displays.

Visual consciousness dynamics in adults with and without autism

Sensory differences between autism and neuro-typical populations are well-documented and have often been explained by either weak-central-coherence or excitation/inhibition-imbalance cortical theories. We tested these theories with perceptual multi-stability paradigms in which dissimilar images presented to each eye generate dynamic cyclopean percepts based on ongoing cortical grouping and suppression processes. We studied perceptual multi-stability with Interocular Grouping (IOG), which requires the simultaneous integration and suppression of image fragments from both eyes, and Conventional Binocular Rivalry (CBR), which only requires global suppression of either eye, in 17 autistic adults and 18 neurotypical participants. We used a Hidden-Markov-Model as tool to analyze the multistable dynamics of these processes. Overall, the dynamics of multi-stable perception were slower (i.e. there were longer durations and fewer transitions among perceptual states) in the autistic group compared to the neurotypical group for both IOG and CBR. The weighted Markovian transition distributions revealed key differences between both groups and paradigms. The results indicate overall lower levels of suppression and decreased levels of grouping in autistic than neurotypical participants, consistent with elements of excitation/inhibition imbalance and weak-central-coherence theories.

Atypical Auditory Perception Caused by Environmental Stimuli in Autism Spectrum Disorder: A Systematic Approach to the Evaluation of Self-Reports

Recent studies have revealed that atypical sensory perception is common in individuals with autism spectrum disorder (ASD) and is considered a potential cause of social difficulties. Self-reports by individuals with ASD have provided great insights into atypical perception from the first-person point of view and indicated its dependence on the environment. This study aimed to investigate the patterns and environmental causes of atypical auditory perception in individuals with ASD. Qualitative data from subject reports are inappropriate for statistical analysis, and reporting subjective sensory experiences is not easy for every individual. To cope with such challenges, we employed audio signal processing methods to simulate the potential patterns of atypical auditory perception. The participants in our experiment were able to select and adjust the strength of the processing methods to manipulate the sounds in the videos to match their experiences. Thus, the strength of atypical perception was recorded quantitatively and then analyzed to assess its correlation with the audio-visual stimuli contained in the videos the participants observed. In total, 22 participants with ASD and 22 typically developed (TD) participants were recruited for the experiment. The results revealed several common patterns of atypical auditory perception: Louder sounds perceived in a quiet environment, noise perception induced by intense and unsteady audio-visual stimuli, and echo perception correlated with movement and variation in sound level. The ASD group reported atypical perceptions more frequently than the control group. However, similar environmental causes were shared by the ASD and TD groups. The results help us infer the potential neural and physiological mechanisms of sensory processing in ASD.

Disorder-specific alterations of tactile sensitivity in neurodevelopmental disorders

Alterations of tactile processing have long been identified in autism spectrum disorders (ASD) and attention-deficit/hyperactivity disorder (ADHD). However, the extent to which these alterations are disorder-specific, rather than disorder-general, and how they relate to the core symptoms of each disorder, remains unclear. We measured and compared tactile detection, discrimination, and order judgment thresholds between a large sample of children with ASD, ADHD, ASD + ADHD combined and typically developing controls. The pattern of results suggested that while difficulties with tactile detection and order judgement were more common in children with ADHD, difficulties with tactile discrimination were more common in children with ASD. Interestingly, in our subsequent correlation analyses between tactile perception and disorder-specific clinical symptoms, tactile detection and order judgment correlated exclusively with the core symptoms of ADHD, while tactile discrimination correlated exclusively with the symptoms of ASD. When taken together, these results suggest that disorder-specific alterations of lower-level sensory processes exist and are specifically related to higher-level clinical symptoms of each disorder.

Investigating the Interaction Between Form and Motion Processing: A Review of Basic Research and Clinical Evidence

A widely held view of the visual system supported the perspective that the primate brain is organized in two main specialized streams, called the ventral and dorsal streams. The ventral stream is known to be involved in object recognition (e.g., form and orientation). In contrast, the dorsal stream is thought to be more involved in spatial recognition (e.g., the spatial relationship between objects and motion direction). Recent evidence suggests that these two streams are not segregated but interact with each other. A class of visual stimuli known as Glass patterns has been developed to shed light on this process. Glass patterns are visual stimuli made of pairs of dots, called dipoles, that give the percept of a specific form or apparent motion, depending on the spatial and temporal arrangement of the dipoles. In this review, we show an update of the neurophysiological, brain imaging, psychophysical, clinical, and brain stimulation studies which have assessed form and motion integration mechanisms, and the level at which this occurs in the human and non-human primate brain. We also discuss several studies based on non-invasive brain stimulation techniques that used different types of visual stimuli to assess the cortico-cortical interactions in the visual cortex for the processing of form and motion information. Additionally, we discuss the timing of specific visual processing in the ventral and dorsal streams. Finally, we report some parallels between healthy participants and neurologically impaired patients in the conscious processing of form and motion.

Autistic traits in synaesthesia: atypical sensory sensitivity and enhanced perception of details

In synaesthetes, specific sensory stimuli (e.g. black letters) elicit additional experiences (e.g. colour). Synaesthesia is highly prevalent among individuals with autism spectrum disorder (ASD), but the mechanisms of this co-occurrence are not clear. We hypothesized autism and synaesthesia share atypical sensory sensitivity and perception. We assessed autistic traits, sensory sensitivity and visual perception in two synaesthete populations. In Study 1, synaesthetes (N = 79, of different types) scored higher than non-synaesthetes (N = 76) on the Attention-to-detail and Social skills subscales of the autism spectrum quotient indexing autistic traits, and on the Glasgow Sensory Questionnaire indexing sensory hypersensitivity and hyposensitivity which frequently occur in autism. Synaesthetes performed two local/global visual tasks because individuals with autism typically show a bias towards detail processing. In synaesthetes, elevated motion coherence thresholds (MCTs) suggested reduced global motion perception, and higher accuracy on an embedded figures task suggested enhanced local perception. In Study 2, sequence-space synaesthetes (N = 18) completed the same tasks. Questionnaire and embedded figures results qualitatively resembled Study 1 results, but no significant group differences with non-synaesthetes (N = 20) were obtained. Unexpectedly, sequence-space synaesthetes had reduced MCTs. Altogether, our studies suggest atypical sensory sensitivity and a bias towards detail processing are shared features of synaesthesia and ASD. This article is part of the discussion meeting issue 'Bridging senses: novel insights from synaesthesia'.

Global Motion Perception in Autism Spectrum Disorder: A Meta-Analysis

Visual perception in individuals with autism spectrum disorder (ASD) is often debated in terms of enhanced local and impaired global perception. Deficits in global motion perception seem to support this characterization, although the evidence is inconsistent. We conducted a large meta-analysis on global motion, combining 48 articles on biological and coherent motion. Results provide evidence for a small global motion processing deficit in individuals with ASD compared to controls in both biological and coherent motion. This deficit appears to be present independent of the paradigm, task, dependent variable, age or IQ of the groups. Results indicate that individuals with ASD are less sensitive to these types of global motion, although the difference in neural mechanisms underlying this behavioral difference remains unclear.

Ayres Theories of Autism and Sensory Integration Revisited: What Contemporary Neuroscience Has to Say

Abnormal sensory-based behaviors are a defining feature of autism spectrum disorders (ASD). Dr. A. Jean Ayres was the first occupational therapist to conceptualize Sensory Integration (SI) theories and therapies to address these deficits. Her work was based on neurological knowledge of the 1970’s. Since then, advancements in neuroimaging techniques make it possible to better understand the brain areas that may underlie sensory processing deficits in ASD. In this article, we explore the postulates proposed by Ayres (i.e., registration, modulation, motivation) through current neuroimaging literature. To this end, we review the neural underpinnings of sensory processing and integration in ASD by examining the literature on neurophysiological responses to sensory stimuli in individuals with ASD as well as structural and network organization using a variety of neuroimaging techniques. Many aspects of Ayres’ hypotheses about the nature of the disorder were found to be highly consistent with current literature on sensory processing in children with ASD but there are some discrepancies across various methodological techniques and ASD development. With additional characterization, neurophysiological profiles of sensory processing in ASD may serve as valuable biomarkers for diagnosis and monitoring of therapeutic interventions, such as SI therapy.

The impact of atypical sensory processing on social impairments in autism spectrum disorder

Altered sensory processing has been an important feature of the clinical descriptions of autism spectrum disorder (ASD). There is evidence that sensory dysregulation arises early in the progression of ASD and impacts social functioning. This paper reviews behavioral and neurobiological evidence that describes how sensory deficits across multiple modalities (vision, hearing, touch, olfaction, gustation, and multisensory integration) could impact social functions in ASD. Theoretical models of ASD and their implications for the relationship between sensory and social functioning are discussed. Furthermore, neural differences in anatomy, function, and connectivity of different regions underlying sensory and social processing are also discussed. We conclude that there are multiple mechanisms through which early sensory dysregulation in ASD could cascade into social deficits across development. Future research is needed to clarify these mechanisms, and specific focus should be given to distinguish between deficits in primary sensory processing and altered top-down attentional and cognitive processes.

Embedded Figures Test Performance in the Broader Autism Phenotype: A Meta-analysis

People with autism show superior performance to controls on the Embedded Figures Test (EFT). However, studies examining the relationship between autistic-like traits and EFT performance in neurotypical individuals have yielded inconsistent findings. To examine the inconsistency, a meta-analysis was conducted of studies that (a) compared high and low Autism-Spectrum Quotient (AQ) groups, and (b) treated AQ as a continuous variable. Outcomes are consistent with superior visual search forming part of the broader autism phenotype, but in existing literature, this is evident only when comparing extreme groups. Reanalysis of data from previous studies suggests findings are unlikely to be driven by a small number of high scorers. Monte Carlo simulations are used to illustrate the effect of methodological differences on results.

An autism-associated serotonin transporter variant disrupts multisensory processing

Altered sensory processing is observed in many children with autism spectrum disorder (ASD), with growing evidence that these impairments extend to the integration of information across the different senses (that is, multisensory function). The serotonin system has an important role in sensory development and function, and alterations of serotonergic signaling have been suggested to have a role in ASD. A gain-of-function coding variant in the serotonin transporter (SERT) associates with sensory aversion in humans, and when expressed in mice produces traits associated with ASD, including disruptions in social and communicative function and repetitive behaviors. The current study set out to test whether these mice also exhibit changes in multisensory function when compared with wild-type (WT) animals on the same genetic background. Mice were trained to respond to auditory and visual stimuli independently before being tested under visual, auditory and paired audiovisual (multisensory) conditions. WT mice exhibited significant gains in response accuracy under audiovisual conditions. In contrast, although the SERT mutant animals learned the auditory and visual tasks comparably to WT littermates, they failed to show behavioral gains under multisensory conditions. We believe these results provide the first behavioral evidence of multisensory deficits in a genetic mouse model related to ASD and implicate the serotonin system in multisensory processing and in the multisensory changes seen in ASD.

Brief Report: Coherent Motion Processing in Autism: Is Dot Lifetime an Important Parameter?

Contrasting reports of reduced and intact sensitivity to coherent motion in autistic individuals may be attributable to stimulus parameters. Here, we investigated whether dot lifetime contributes to elevated thresholds in children with autism. We presented a standard motion coherence task to 31 children with autism and 31 typical children, with both limited and unlimited lifetime conditions. Overall, children had higher thresholds in the limited lifetime condition than in the unlimited lifetime condition. However, children with autism were affected by this manipulation to the same extent as typical children and were equally sensitive to coherent motion. Our results suggest that dot lifetime is not a critical stimulus parameter and speak against pervasive difficulties in coherent motion perception in children with autism.

Motion perception: a review of developmental changes and the role of early visual experience

Significant controversies have arisen over the developmental trajectory for the perception of global motion. Studies diverge on the age at which it becomes adult-like, with estimates ranging from as young as 3 years to as old as 16. In this article, we review these apparently conflicting results and suggest a potentially unifying hypothesis that may also account for the contradictory literature in neurodevelopmental disorders, such as Autism Spectrum Disorder (ASD). We also discuss the extent to which patterned visual input during this period is necessary for the later development of motion perception. We conclude by addressing recent studies directly comparing different types of motion integration, both in typical and atypical development, and suggest areas ripe for future research.

Behavioral evidence for a functional link between low- and mid-level visual perception in the autism spectrum

BACKGROUND

Most investigations of visuo-perceptual abilities in the Autism Spectrum (AS) are level-specific, using tasks that selectively solicit either lower- (i.e., spatial frequency sensitivity), mid- (i.e., pattern discrimination) or higher-level processes (i.e., face identification) along the visual hierarchy. Less is known about how alterations at one level of processing (i.e., low-level) interact with that of another (i.e., mid-level). The aim of this study was to assess whether manipulating the physical properties (luminance vs texture) of local contour elements of a mid-level, visual pattern interferes with the discrimination of that pattern in a differential manner for individuals with AS.

METHODS

Twenty-nine AS individuals and thirty control participants (range 14-27 years) were asked to discriminate between perfect circles and Radial Frequency Patterns (RFP) of two, three, five, and 10 radial frequencies (RF), or deformations along the pattern's contour. When RFP have few deformations (<five RF), a global, pattern analysis is needed for shape discrimination. Conversely, when RFP contain many deformations (≥10 RF), discrimination is dependent on the analysis of local deformations along the RFP contour. The effect of manipulating RF on RFP discrimination was assessed for RFP whose local contour elements were defined by either luminance or texture information, the latter previously found less efficiently processed in AS individuals.

RESULTS

Two separate mixed factorial ANOVAs [2 (Group)×4 (RF)] were conducted on mean deformation thresholds for luminance- and texture-defined conditions. A significant Group×RF interaction was found for the luminance-defined condition where thresholds were higher in the AS group for the two and three RF conditions; no between-group differences were found for the five and 10 RF conditions. A significant main effect of group was identified for the texture-defined condition, where mean thresholds were higher for the AS group across all RF conditions assessed (two, three, five and 10); a Group×RF interaction effect was not found. Performance for each RFP condition was not affected across group by either chronological age or intelligence, as measured by either Weschler scales or Raven Progressive Matrices.

CONCLUSIONS

The ability of AS individuals to discriminate a circular pattern is differentially affected by the availability (number of deformations along the RFP contour) and type (luminance vs texture) of local, low-level elements defining its contour. Performance is unaffected in AS when RFP discrimination is dependent on the analysis of local deformations of luminance-defined contour elements, but decreased across all RF conditions when local contour elements are texture-defined. These results suggest that efficient pattern perception in AS is functionally related to the efficacy with which its local elements are processed, indicative of an early origin for altered mid-level, pattern perception in AS.

Judging the Intensity of Emotional Expression in Faces: the Effects of Colored Tints on Individuals With Autism Spectrum Disorder

Individuals with autism spectrum disorder (ASD) often show atypical processing of facial expressions, which may result from visual stress. In the current study, children with ASD and matched controls judged which member of a pair of faces displayed the more intense emotion. Both faces showed anger, disgust, fear, happiness, sadness or surprise but to different degrees. Faces were presented on a monitor that was tinted either gray or with a color previously selected by the participant individually as improving the clarity of text. Judgments of emotional intensity improved significantly with the addition of the preferred colored tint in the ASD group but not in controls, a result consistent with a link between visual stress and impairments in processing facial expressions in individuals with ASD.

Self-motion perception in autism is compromised by visual noise but integrated optimally across multiple senses

Perceptual processing in autism spectrum disorder (ASD) is marked by superior low-level task performance and inferior complex-task performance. This observation has led to theories of defective integration in ASD of local parts into a global percept. Despite mixed experimental results, this notion maintains widespread influence and has also motivated recent theories of defective multisensory integration in ASD. Impaired ASD performance in tasks involving classic random dot visual motion stimuli, corrupted by noise as a means to manipulate task difficulty, is frequently interpreted to support this notion of global integration deficits. By manipulating task difficulty independently of visual stimulus noise, here we test the hypothesis that heightened sensitivity to noise, rather than integration deficits, may characterize ASD. We found that although perception of visual motion through a cloud of dots was unimpaired without noise, the addition of stimulus noise significantly affected adolescents with ASD, more than controls. Strikingly, individuals with ASD demonstrated intact multisensory (visual-vestibular) integration, even in the presence of noise. Additionally, when vestibular motion was paired with pure visual noise, individuals with ASD demonstrated a different strategy than controls, marked by reduced flexibility. This result could be simulated by using attenuated (less reliable) and inflexible (not experience-dependent) Bayesian priors in ASD. These findings question widespread theories of impaired global and multisensory integration in ASD. Rather, they implicate increased sensitivity to sensory noise and less use of prior knowledge in ASD, suggesting increased reliance on incoming sensory information.

Categorizing identity from facial motion

Advances in marker-less motion capture technology now allow the accurate replication of facial motion and deformation in computer-generated imagery (CGI). A forced-choice discrimination paradigm using such CGI facial animations showed that human observers can categorize identity solely from facial motion cues. Animations were generated from motion captures acquired during natural speech, thus eliciting both rigid (head rotations and translations) and nonrigid (expressional changes) motion. To limit interferences from individual differences in facial form, all animations shared the same appearance. Observers were required to discriminate between different videos of facial motion and between the facial motions of different people. Performance was compared to the control condition of orientation-inverted facial motion. The results show that observers are able to make accurate discriminations of identity in the absence of all cues except facial motion. A clear inversion effect in both tasks provided consistency with previous studies, supporting the configural view of human face perception. The accuracy of this motion capture technology thus allowed stimuli to be generated that closely resembled real moving faces. Future studies may wish to implement such methodology when studying human face perception.

Temporal processing as a source of altered visual perception in high autistic tendency

Superior local at the expense of global perception characterises vision in autism spectrum disorders (ASD). However, progress towards discovering a neural mechanism has been slow. Here we used known differences in magnocellular and parvocellular receptive field properties to assess the temporal encoding of information, via flicker fusion paradigms, in those high and low in self-reported autistic tendency (Autism Spectrum Quotient - AQ). A Low AQ group (AQ≤13, n=22), and a High AQ group (AQ≥18, n=17) undertook a 4AFC luminance flicker fusion (FF) with 5 temporal contrasts from 5% to 100%, and a 2AFC isoluminant red-green colour fusion task. Both groups showed an increase in fusion thresholds with temporal achromatic contrast. The High AQ group displayed diminished flicker fusion thresholds compared to the Low AQ at the lowest contrasts. For the red-green colour fusion task, the High AQ group displayed mean fusion frequency slightly greater than the Low AQ group. A significant interaction between 5% luminance contrast and the red-green fusion frequencies demonstrated that the differences in thresholds were not simply due to variations in overall attentional capacity between groups. These differences in flicker fusion thresholds are in accordance with reported differences in cortical visual evoked potential nonlinearities, particularly relating to the neural efficiency of the magnocellular pathway.

The construct of the multisensory temporal binding window and its dysregulation in developmental disabilities

Behavior, perception and cognition are strongly shaped by the synthesis of information across the different sensory modalities. Such multisensory integration often results in performance and perceptual benefits that reflect the additional information conferred by having cues from multiple senses providing redundant or complementary information. The spatial and temporal relationships of these cues provide powerful statistical information about how these cues should be integrated or "bound" in order to create a unified perceptual representation. Much recent work has examined the temporal factors that are integral in multisensory processing, with many focused on the construct of the multisensory temporal binding window - the epoch of time within which stimuli from different modalities is likely to be integrated and perceptually bound. Emerging evidence suggests that this temporal window is altered in a series of neurodevelopmental disorders, including autism, dyslexia and schizophrenia. In addition to their role in sensory processing, these deficits in multisensory temporal function may play an important role in the perceptual and cognitive weaknesses that characterize these clinical disorders. Within this context, focus on improving the acuity of multisensory temporal function may have important implications for the amelioration of the "higher-order" deficits that serve as the defining features of these disorders.

Asperger's disorder will be back

This review focuses on identifying up-to-date number of publications that compared DSM-IV/ICD-10 Asperger's disorder (AspD) to Autistic Disorder/High-functioning Autism (AD/HFA). One hundred and twenty-eight publications were identified through an extensive search of major electronic databases and journals. Based on more than 90 clinical variables been investigated, 94 publications concluded that there were statistically significant or near significant level of quantitative and/or qualitative differences between AspD and AD/HFA groups; 4 publications found both similarities and differences between the two groups; 30 publications concluded with no differences between the two groups. Although DSM-5 ASD will eliminate Asperger's disorder. However, it is plausible to predict that the field of ASD would run full circle during the next decade or two and that AspD will be back in the next edition of DSM.

Impaired perception of facial motion in autism spectrum disorder

Facial motion is a special type of biological motion that transmits cues for socio-emotional communication and enables the discrimination of properties such as gender and identity. We used animated average faces to examine the ability of adults with autism spectrum disorders (ASD) to perceive facial motion. Participants completed increasingly difficult tasks involving the discrimination of (1) sequences of facial motion, (2) the identity of individuals based on their facial motion and (3) the gender of individuals. Stimuli were presented in both upright and upside-down orientations to test for the difference in inversion effects often found when comparing ASD with controls in face perception. The ASD group’s performance was impaired relative to the control group in all three tasks and unlike the control group, the individuals with ASD failed to show an inversion effect. These results point to a deficit in facial biological motion processing in people with autism, which we suggest is linked to deficits in lower level motion processing we have previously reported.

Neural responses to emotional expression information in high- and low-spatial frequency in autism: evidence for a cortical dysfunction

Despite an overall consensus that Autism Spectrum Disorder (ASD) entails atypical processing of human faces and emotional expressions, the role of neural structures involved in early facial processing remains unresolved. An influential model for the neurotypical brain suggests that face processing in the fusiform gyrus and the amygdala is based on both high-spatial frequency (HSF) information carried by a parvocellular pathway, and low-spatial frequency (LSF) information separately conveyed by a magnocellular pathway. Here, we tested the fusiform gyrus and amygdala sensitivity to emotional face information conveyed by these distinct pathways in ASD individuals (and matched Controls). During functional Magnetical Resonance Imaging (fMRI), participants reported the apparent gender of hybrid face stimuli, made by merging two different faces (one in LSF and the other in HSF), out of which one displayed an emotional expression (fearful or happy) and the other was neutral. Controls exhibited increased fusiform activity to hybrid faces with an emotional expression (relative to hybrids composed only with neutral faces), regardless of whether this was conveyed by LSFs or HSFs in hybrid stimuli. ASD individuals showed intact fusiform response to LSF, but not HSF, expressions. Furthermore, the amygdala (and the ventral occipital cortex) was more sensitive to HSF than LSF expressions in Controls, but exhibited an opposite preference in ASD. Our data suggest spared LSF face processing in ASD, while cortical analysis of HSF expression cues appears affected. These findings converge with recent accounts suggesting that ASD might be characterized by a difficulty in integrating multiple local information and cause global processing troubles unexplained by losses in low spatial frequency inputs.

Multiple object tracking in autism spectrum disorders

Difficulties in visual attention are often implicated in autism spectrum disorders (ASD) but it remains unclear which aspects of attention are affected. Here, we used a multiple object tracking (MOT) task to quantitatively characterize dynamic attentional function in children with ASD aged 5-12. While the ASD group performed significantly worse overall, the group difference did not increase with increased object speed. This finding suggests that decreased MOT performance is not due to deficits in dynamic attention but instead to a diminished capacity to select and maintain attention on multiple targets. Further, MOT performance improved from 5 to 10 years in both typical and ASD groups with similar developmental trajectories. These results argue against a specific deficit in dynamic attention in ASD.

Luminance- and texture-defined information processing in school-aged children with autism

According to the complexity-specific hypothesis, the efficacy with which individuals with autism spectrum disorder (ASD) process visual information varies according to the extensiveness of the neural network required to process stimuli. Specifically, adults with ASD are less sensitive to texture-defined (or second-order) information, which necessitates the implication of several cortical visual areas. Conversely, the sensitivity to simple, luminance-defined (or first-order) information, which mainly relies on primary visual cortex (V1) activity, has been found to be either superior (static material) or intact (dynamic material) in ASD. It is currently unknown if these autistic perceptual alterations are present in childhood. In the present study, behavioural (threshold) and electrophysiological measures were obtained for static luminance- and texture-defined gratings presented to school-aged children with ASD and compared to those of typically developing children. Our behavioural and electrophysiological (P140) results indicate that luminance processing is likely unremarkable in autistic children. With respect to texture processing, there was no significant threshold difference between groups. However, unlike typical children, autistic children did not show reliable enhancements of brain activity (N230 and P340) in response to texture-defined gratings relative to luminance-defined gratings. This suggests reduced efficiency of neuro-integrative mechanisms operating at a perceptual level in autism. These results are in line with the idea that visual atypicalities mediated by intermediate-scale neural networks emerge before or during the school-age period in autism.

Prospective examination of visual attention during play in infants at high-risk for autism spectrum disorder: a longitudinal study from 6 to 36 months of age

Regulation of visual attention is essential to learning about one's environment. Children with autism spectrum disorder (ASD) exhibit impairments in regulating their visual attention, but little is known about how such impairments develop over time. This prospective longitudinal study is the first to describe the development of components of visual attention, including engaging, sustaining, and disengaging attention, in infants at high-risk of developing ASD (each with an older sibling with ASD). Non-sibling controls and high-risk infant siblings were filmed at 6, 9, 12, 15, 18, 24, and 36 months of age as they engaged in play with small, easily graspable toys. Duration of time spent looking at toy targets before moving the hand toward the target and the duration of time spent looking at the target after grasp were measured. At 36 months of age, an independent, gold standard diagnostic assessment for ASD was conducted for all participants. As predicted, infant siblings subsequently diagnosed with ASD were distinguished by prolonged latency to disengage ('sticky attention') by 12 months of age, and continued to show this characteristic at 15, 18, and 24 months of age. The results are discussed in relation to how the development of visual attention may impact later cognitive outcomes of children diagnosed with ASD.

The temporal dynamics of coherent motion processing in autism spectrum disorder: evidence for a deficit in the dorsal pathway

Individuals with autism spectrum disorder (ASD) show impairments in processing coherent motion which have been proposed to be linked to a general deficit in the dorsal visual pathway. However, few studies have investigated the neural mechanisms underlying coherent motion processing in ASD. Thus, the aim of this study was to further test the hypothesis of a dorsal pathway deficit in ASD using visual evoked potentials (VEPs). 16 children and adolescents with ASD and 12 typically developing controls were examined with VEPs elicited by a random dot kinematogram. After an initial experimental sequence, where subjects were presented randomly moving dots, a fraction of the dots moved coherently (dependent on the level of coherence, 20%, 40%, or 60% of the dots) to the left or right side. Subjects were asked to detect the direction of coherent motion via button press. On the behavioural level, no significant group differences emerged. On the neural level, coherently moving dots elicited a N200 followed by a late positive potential (P400). ASD subjects exhibited a reduced N200 amplitude compared to controls. Moreover, in the ASD group, a trend for a negative relationship between N200 amplitude and a measure of autistic pathology was revealed. The present study provides strong support of a dorsal stream deficiency in the disorder and renders alternative explanations for impaired coherent motion processing in ASD less likely. Together with findings from related research fields, our data indicate that deviances in the N200 during coherent motion perception might be fundamental to ASD.

Electrophysiological evidence of atypical visual change detection in adults with autism

Although atypical change detection processes have been highlighted in the auditory modality in autism spectrum disorder (ASD), little is known about these processes in the visual modality. The aim of the present study was therefore to investigate visual change detection in adults with ASD, taking into account the salience of change, in order to determine whether this ability is affected in this disorder. Thirteen adults with ASD and 13 controls were presented with a passive visual three stimuli oddball paradigm. The findings revealed atypical visual change processing in ASD. Whereas controls displayed a vMMN in response to deviant and a novelty P3 in response to novel stimuli, patients with ASD displayed a novelty P3 in response to both deviant and novel stimuli. These results thus suggested atypical orientation of attention toward unattended minor changes in ASD that might contribute to the intolerance of change.

Visuomotor resonance in autism spectrum disorders

When we observe the actions performed by others, our motor system “resonates” along with that of the observed agent. Is a similar visuomotor resonant response observed in autism spectrum disorders (ASD)? Studies investigating action observation in ASD have yielded inconsistent findings. In this perspective article we examine behavioral and neuroscientific evidence in favor of visuomotor resonance in ASD, and consider the possible role of action-perception coupling in social cognition. We distinguish between different aspects of visuomotor resonance and conclude that while some aspects may be preserved in ASD, abnormalities exist in the way individuals with ASD convert visual information from observed actions into a program for motor execution. Such abnormalities, we surmise, may contribute to but also depend on the difficulties that individuals with ASD encounter during social interaction.

Atypical integration of motion signals in Autism Spectrum Conditions

Vision in Autism Spectrum Conditions (ASC) is characterized by enhanced perception of local elements, but impaired perception of global percepts. Deficits in coherent motion perception seem to support this characterization, but the roots and robustness of such deficits remain unclear. We aimed to investigate the dynamics of the perceptual decision-making network known to support coherent motion perception. In a series of forced-choice coherent motion perception tests, we parametrically varied a single stimulus dimension, viewing duration, to test whether the rate at which evidence is accumulated towards a global decision is atypical in ASC. 40 adult participants (20 ASC) performed a classic motion discrimination task, manually indicating the global direction of motion in a random-dot kinematogram across a range of coherence levels (2-75%) and stimulus-viewing durations (200-1500 ms). We report a deficit in global motion perception at short viewing durations in ASC. Critically, however, we found that increasing the amount of time over which motion signals could be integrated reduced the magnitude of the deficit, such that at the longest duration there was no difference between the ASC and control groups. Further, the deficit in motion integration at the shortest duration was significantly associated with the severity of autistic symptoms in our clinical population, and was independent from measures of intelligence. These results point to atypical integration of motion signals during the construction of a global percept in ASC. Based on the neural correlates of decision-making in global motion perception our findings suggest the global motion deficit observed in ASC could reflect a slower or more variable response from the primary motion area of the brain or longer accumulation of evidence towards a decision-bound in parietal areas.

Visual processing in Noonan syndrome: dorsal and ventral stream sensitivity

Global spatial and motion processing abilities were assessed in 18 patients with Noonan syndrome (NS) and in 43 matched controls using form and motion coherence testing, respectively. We observed a discrepancy between the two groups since the study group had significantly lower performances than the control group for form coherence while there was no impairment on motion coherence. All the patients were also assessed on the Movement Assessment Battery for Children (M-ABC) to evaluate visuomotor skills. Thirteen of the 18 (72%) also had global poor performances on the M-ABC. The results show that children with NS have a specific impairment in the global processing of visuospatial information and are likely to have a specific ventral stream deficit as also suggested by the frequent visuomotor perceptual difficulties. Testing form and motion coherence thresholds may be a useful diagnostic tool for this group of patients, despite their normal cognitive abilities, since aspects of global form processing and visuomotor perceptual difficulties can be identified and potentially targeted for a specific rehabilitation program.

Confusion and inconsistency in diagnosis of Asperger syndrome: a review of studies from 1981 to 2010

This paper presents a review of past and current research on the diagnosis of Asperger syndrome (AS) in children. It is suggested that the widely used criteria for diagnosing AS in the Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV are insufficient and invalid for a reliable diagnosis of AS. In addition, when these diagnostic criteria are applied, there is the potential bias of receiving a diagnosis towards the high-functioning end of the autism spectrum. Through a critical review of 69 research studies carried out between 1981 and 2010, this paper shows that six possible criteria for diagnosing AS (specifically, the age at which signs and symptoms related to autism become apparent, language and social communication abilities, intellectual abilities, motor or movement skills, repetitive patterns of behaviour and the nature of social interaction) overlap with the criteria for diagnosing autism. However, there is a possibility that some finer differences exist in the nature of social interaction, motor skills and speech patterns between groups with a diagnosis of AS and autism. These findings are proposed to be of relevance for designing intervention studies aimed at the treatment of specific symptoms in people with an autism spectrum disorder.

A clínica da psicofísica

Apresentamos a Psicofísica como uma ciência aplicada nas investigações e nas abordagens e diagnósticos clínicos. Inicialmente, introduzimos algo dos aspectos epistemológicos e teóricos da área, passamos para as abordagens que a Psicofísica pode apresentar na aplicabilidade clínica e, por fim, discutimos os avanços recentes da aplicação clínica, apresentamos as experiências de nosso laboratório de pesquisa clínica em psicofísica, finalizando com as perspectivas de ampliação do uso da psicofísica para investigações clínicas de funções perceptuais mais complexas.

Using perceptual signatures to define and dissociate condition-specific neural etiology: autism and fragile X syndrome as model conditions

The functional link between genetic alteration and behavioral end-state is rarely straightforward and never linear. Cases where neurodevelopmental conditions defined by a distinct genetic etiology share behavioral phenotypes are exemplary, as is the case for autism and Fragile X Syndrome (FXS). In this paper and its companion paper, we propose a method for assessing the functional link between genotype and neural alteration across these target conditions by comparing their perceptual signatures. In the present paper, we discuss how such signatures can be used to (1) define and differentiate various aspects of neural functioning in autism and FXS, and subsequently, (2) to infer candidate causal (genetic) mechanisms based on such signatures (see companion paper, this issue).

Development of motion processing in children with autism

Recent findings suggest that children with autism may be impaired in the perception of biological motion from moving point-light displays. Some children with autism also have abnormally high motion coherence thresholds. In the current study we tested a group of children with autism and a group of typically developing children aged 5 to 12 years of age on several motion perception tasks, in order to establish the specificity of the biological motion deficit in relation to other visual discrimination skills. The first task required the recognition of biological from scrambled motion. Three quasi-psychophysical tasks then established individual thresholds for the detection of biological motion in dynamic noise, of motion coherence and of form-from-motion. Lastly, individual thresholds for a task of static perception--contour integration (Gabor displays)--were also obtained. Compared to controls, children with autism were particularly impaired in processing biological motion in relation to any developmental measure (chronological or mental age). In contrast, there was some developmental overlap in ability to process other types of visual motion between typically developing children and the children with autism, and evidence of developmental change in both groups. Finally, Gabor display thresholds appeared to develop typically in children with autism.

Contrast sensitivity for motion detection and direction discrimination in adolescents with autism spectrum disorders and their siblings

The magnocellular (M) pathway hypothesis proposes that impaired visual motion perception observed in individuals with Autism Spectrum Disorders (ASD) might be mediated by atypical functioning of the subcortical M pathway, as this pathway provides the bulk of visual input to cortical motion detectors. To test this hypothesis, we measured luminance and chromatic contrast sensitivity, thought to tap M and Parvocellular (P) pathway processing, respectively. We also tested the hypothesis that motion processing is impaired in ASD using a novel paradigm that measures motion processing while controlling for detectabilty. Specifically, this paradigm compares contrast sensitivity for detection of a moving grating with contrast sensitivity for direction-of-motion discrimination of that same moving grating. Contrast sensitivities from adolescents with ASD were compared to typically-developing adolescents, and also unaffected siblings of individuals with ASD (SIBS). The results revealed significant group differences on P, but not M, pathway processing, with SIBS showing higher chromatic contrast sensitivity than both participants with ASD and TD participants. This atypicality, unique to SIBS, suggests the possible existence of a protective factor in these individuals against developing ASD. The results also revealed impairments in motion perception in both participants with ASD and SIBS, which may be an endophenotype of ASD. This impairment may be driven by impairments in motion detectors and/or by reduced input from neural areas that project to motion detectors, the latter possibility being consistent with the notion of reduced connectivity between neural areas in ASD.

Unaffected perceptual thresholds for biological and non-biological form-from-motion perception in autism spectrum conditions

BACKGROUND

Perception of biological motion is linked to the action perception system in the human brain, abnormalities within which have been suggested to underlie impairments in social domains observed in autism spectrum conditions (ASC). However, the literature on biological motion perception in ASC is heterogeneous and it is unclear whether deficits are specific to biological motion, or might generalize to form-from-motion perception.

METHODOLOGY AND PRINCIPAL FINDINGS

We compared psychophysical thresholds for both biological and non-biological form-from-motion perception in adults with ASC and controls. Participants viewed point-light displays depicting a walking person (Biological Motion), a translating rectangle (Structured Object) or a translating unfamiliar shape (Unstructured Object). The figures were embedded in noise dots that moved similarly and the task was to determine direction of movement. The number of noise dots varied on each trial and perceptual thresholds were estimated adaptively. We found no evidence for an impairment in biological or non-biological object motion perception in individuals with ASC. Perceptual thresholds in the three conditions were almost identical between the ASC and control groups.

DISCUSSION AND CONCLUSIONS

Impairments in biological motion and non-biological form-from-motion perception are not across the board in ASC, and are only found for some stimuli and tasks. We discuss our results in relation to other findings in the literature, the heterogeneity of which likely relates to the different tasks performed. It appears that individuals with ASC are unaffected in perceptual processing of form-from-motion, but may exhibit impairments in higher order judgments such as emotion processing. It is important to identify more specifically which processes of motion perception are impacted in ASC before a link can be made between perceptual deficits and the higher-level features of the disorder.

Perception of shapes targeting local and global processes in autism spectrum disorders

BACKGROUND

Several researchers have found evidence for impaired global processing in the dorsal visual stream in individuals with autism spectrum disorders (ASDs). However, support for a similar pattern of visual processing in the ventral visual stream is less consistent. Critical to resolving the inconsistency is the assessment of local and global form processing ability.

METHODS

Within the visual domain, radial frequency (RF) patterns - shapes formed by sinusoidally varying the radius of a circle to add 'bumps' of a certain number to a circle - can be used to examine local and global form perception. Typically developing children and children with an ASD discriminated between circles and RF patterns that are processed either locally (RF24) or globally (RF3).

RESULTS

Children with an ASD required greater shape deformation to identify RF3 shapes compared to typically developing children, consistent with difficulty in global processing in the ventral stream. No group difference was observed for RF24 shapes, suggesting intact local ventral-stream processing.

CONCLUSIONS

These outcomes support the position that a deficit in global visual processing is present in ASDs, consistent with the notion of Weak Central Coherence.

Vision in developmental disorders: is there a dorsal stream deficit?

The main aim of this review is to evaluate the proposal that several developmental disorders affecting vision share an impairment of the dorsal visual stream. First, the current definitions and common measurement approaches used to assess differences in both local and global functioning within the visual system are considered. Next, studies assessing local and global processing in the dorsal and ventral visual pathways are reviewed for five developmental conditions for which early to mid level visual abilities have been assessed: developmental dyslexia, autism spectrum disorders, developmental dyspraxia, Williams syndrome and Fragile X syndrome. The reviewed evidence is broadly consistent with the idea that the dorsal visual stream is affected in developmental disorders. However, the potential for a unique profile of visual abilities that distinguish some of the conditions is posited, given that for some of these disorders ventral stream deficits have also been found. We conclude with ideas regarding future directions for the study of visual perception in children with developmental disorders using psychophysical measures.

Coherent motion processing in autism spectrum disorder (ASD): an fMRI study

A deficit in global motion processing caused by a specific dysfunction of the visual dorsal pathway has been suggested to underlie perceptual abnormalities in subjects with autism spectrum disorders (ASD). However, the neural mechanisms associated with abnormal motion processing in ASD remain poorly understood. We investigated brain responses related to the detection of coherent and random motion in 15 male subjects with ASD and 15 age- and IQ-matched healthy controls (aged 13-19 years) using event-related functional magnetic resonance imaging (fMRI). Behaviorally, no significant group differences were observed between subjects with ASD and controls. Neurally, subjects with ASD showed increased brain activation in the left primary visual cortex across all conditions compared with controls. A significant interaction effect between group and condition was observed in the right superior parietal cortex resulting from increased neural activity in the coherent compared with the random motion conditions only in the control group. In addition, neural activity in area V5 was not differentially modulated by specific motion conditions in subjects with ASD. Functional connectivity analyses revealed positive correlations between the primary visual cortex and area V5 within both hemispheres, but no significant between-group differences in functional connectivity patterns along the dorsal stream. The data suggest that motion processing in ASD results in deviant activations in both the lower and higher processing stages of the dorsal pathway. This might reflect differences in the perception of visual stimuli in ASD, which possibly result in impaired integration of motion signals.

The visual perception of motion by observers with autism spectrum disorders: a review and synthesis

Traditionally, psychological research on autism spectrum disorder (ASD) has focused on social and cognitive abilities. Vision provides an important input channel to both of these processes, and, increasingly, researchers are investigating whether observers with ASD differ from typical observers in their visual percepts. Recently, significant controversies have arisen over whether observers with ASD differ from typical observers in their visual analyses of movement. Initial studies suggested that observers with ASD experience significant deficits in their visual sensitivity to coherent motion in random dot displays but not to point-light displays of human motion. More recent evidence suggests exactly the opposite: that observers with ASD do not differ from typical observers in their visual sensitivity to coherent motion in random dot displays, but do differ from typical observers in their visual sensitivity to human motion. This review examines these apparently conflicting results, notes gaps in previous findings, suggests a potentially unifying hypothesis, and identifies areas ripe for future research.

The psychophysics of visual motion and global form processing in autism

Several groups have recently reported that people with autism may suffer from a deficit in visual motion processing and proposed that these deficits may be related to a general dorsal stream dysfunction. In order to test the dorsal stream deficit hypothesis, we investigated coherent and biological motion perception as well as coherent form perception in a group of adolescents with autism and a group of age-matched typically developing controls. If the dorsal stream hypothesis were true, we would expect to document deficits in both coherent and biological motion processing in this group but find no deficit in coherent form perception. Using the method of constant stimuli and standard psychophysical analysis techniques, we measured thresholds for coherent motion, biological motion and coherent form. We found that adolescents with autism showed reduced sensitivity to both coherent and biological motion but performed as well as age-matched controls during coherent form perception. Correlations between intelligence quotient and task performance, however, appear to drive much of the group difference in coherent motion perception. Differences between groups on coherent motion perception did not remain significant when intelligence quotient was controlled for, but group differences in biological motion perception were more robust, remaining significant even when intelligence quotient differences were accounted for. Additionally, aspects of task performance on the biological motion perception task were related to autism symptomatology. These results do not support a general dorsal stream dysfunction in adolescents with autism but provide evidence of a more complex impairment in higher-level dynamic attentional processes.

Vision in autism spectrum disorders

Autism spectrum disorders (ASDs) are developmental disorders which are thought primarily to affect social functioning. However, there is now a growing body of evidence that unusual sensory processing is at least a concomitant and possibly the cause of many of the behavioural signs and symptoms of ASD. A comprehensive and critical review of the phenomenological, empirical, neuroscientific and theoretical literature pertaining to visual processing in ASD is presented, along with a brief justification of a new theory which may help to explain some of the data, and link it with other current hypotheses about the genetic and neural aetiologies of this enigmatic condition.

No evidence for impaired perception of biological motion in adults with autistic spectrum disorders

A central feature of autistic spectrum disorders (ASDs) is a difficulty in identifying and reading human expressions, including those present in the moving human form. One previous study, by Blake et al. (2003), reports decreased sensitivity for perceiving biological motion in children with autism, suggesting that perceptual anomalies underlie problems in social cognition. We revisited this issue using a novel psychophysical task. 16 adults with ASDs and 16 controls were asked to detect the direction of movement of human point-light walkers which were presented in both normal and spatially scrambled forms in a background of noise. Unlike convention direction discrimination tasks, in which walkers walk 'on the spot' while facing left or right, we added translatory motion to the stimulus so that the walkers physically moved across the screen. Therefore, while a cue of coherent, translatory motion was available in both the normal and scrambled walker forms, the normal walker alone contained information about the configuration and kinematics of the human body. There was a significant effect of walker type, with reduced response times and error when the normal walker was present. Most importantly, these improvements were the same for both participant groups, suggesting that people with ASDs do not have difficulty integrating local visual information into a global percept of the moving human form. The discrepancy between these and previous findings of impaired biological motion perception in ASDs are discussed with reference to differences in the age and diagnosis of the participants, and the nature of the task.

Reduced sensitivity to minimum-jerk biological motion in autism spectrum conditions

We compared psychophysical thresholds for biological and non-biological motion detection in adults with autism spectrum conditions (ASCs) and controls. Participants watched animations of a biological stimulus (a moving hand) or a non-biological stimulus (a falling tennis ball). The velocity profile of the movement was varied between 100% natural motion (minimum-jerk (MJ) for the hand; gravitational (G) for the ball) and 100% constant velocity (CV). Participants were asked to judge which animation was ‘less natural’ in a two-interval forced-choice paradigm and thresholds were estimated adaptively. There was a significant interaction between group and condition. Thresholds in the MJ condition were lower than in the G condition for the NC group whereas there was no difference between the thresholds in the two conditions for the ASC group. Thus, unlike the controls, the ASC group did not show an increased sensitivity for perturbation to biological over non-biological velocity profiles.