Developmental deficits in social perception in autism: the role of the amygdala and fusiform face area

Abnormal fear conditioning and amygdala processing in an animal model of autism

A core feature of autism spectrum disorders is the impairment in social interactions. Among other brain regions, a deficit in amygdala processing has been suggested to underlie this impairment, but whether the amygdala is processing fear abnormally in autism, is yet not clear. We used the valproic acid (VPA) rat model of autism to (a) screen for autism-like symptoms in rats, (b) test for alterations in amygdala-dependent fear processing, and (c) evaluate neuronal reactivity and synaptic plasticity in the lateral amygdala by means of in vitro single-cell electrophysiological recordings. VPA-treated animals displayed several symptoms common to autism, among them impaired social interactions and increased repetitive behaviors. Furthermore, VPA-treated rats were more anxious and exhibited abnormally high and longer lasting fear memories, which were overgeneralized and harder to extinguish. On the cellular level, the amygdala was hyperreactive to electrical stimulation and displayed boosted synaptic plasticity as well as a deficit in inhibition. We show for the first time enhanced, overgeneralized and resistant conditioned fear memories in an animal model of autism. Such hyperfear could be caused by the hyperreactivity and hyperplasticity found in the lateral amygdala, which may in turn be due to a deficit in the inhibitory system of the amygdala. We hypothesize an 'aversive world' syndrome that could, even if not a primary cause of the disorder itself, underlie some core symptoms in autism, such as impairments in social interactions and resistance to rehabilitation.

Brief report: young adults with autism spectrum disorder show normal attention to eye-gaze information-evidence from a new change blindness paradigm

Other people's eye-gaze is a powerful social stimulus that captures and directs visual attention. There is evidence that this is not the case for children with autism spectrum disorder (ASD), although less is known about attention to eye-gaze in adults. We investigated whether young adults would detect a change to the direction of eye-gaze in another's face more efficiently than a control change (presence/absence of spectacles). A change blindness method was used in which images showed faces as part of a complex, naturalistic scene. Results showed that adults with ASD, like typically developing controls, were faster and more accurate at detecting eye-gaze than control changes. Results are considered in terms of a developmental account of the relationship between social attention and other skills.

A genetic model for understanding higher order visual processing: functional interactions of the ventral visual stream in Williams syndrome

Williams syndrome (WS) is a rare neurodevelopmental disorder caused by a 1.6 Mb microdeletion on chromosome 7q11.23 and characterized by hypersocial personality and prominent visuospatial construction impairments. Previous WS studies have identified functional and structural abnormalities in the hippocampal formation, prefrontal regions crucial for amygdala regulation and social cognition, and the dorsal visual stream, notably the intraparietal sulcus (IPS). Although aberrant ventral stream activation has not been found in WS, object-related visual information that is processed in the ventral stream is a critical source of input into these abnormal regions. The present study, therefore, examined neural interactions of ventral stream areas in WS. Using a passive face- and house-viewing paradigm, activation and functional connectivity of stimulus-selective regions in fusiform and parahippocampal gyri, respectively, were investigated. During house viewing, significant activation differences were observed between participants with WS and a matched control group in IPS. Abnormal functional connectivity was found between parahippocampal gyrus and parietal cortex and between fusiform gyrus and a network of brain regions including amygdala and portions of prefrontal cortex. These results indicate that abnormal upstream visual object processing may contribute to the complex cognitive/behavioral phenotype in WS and provide a systems-level characterization of genetically mediated abnormalities of neural interactions.

fMRI investigation of working memory for faces in autism: visual coding and underconnectivity with frontal areas

Brain activation and functional connectivity were investigated in high functioning autism using functional magnetic resonance imaging in an n-back working memory task involving photographic face stimuli. The autism group showed reliably lower activation compared with controls in the inferior left prefrontal area (involved in verbal processing and working memory maintenance) and the right posterior temporal area (associated with theory of mind processing). The participants with autism also showed activation in a somewhat different location in the fusiform area than the control participants. These results suggest that the neural circuitry of the brain for face processing in autism may be analyzing the features of the face more as objects and less in terms of their human significance. The functional connectivity results revealed that the abnormal fusiform activation was embedded in a larger context of smaller and less synchronized networks, particularly indicating lower functional connectivity with frontal areas. In contrast to the underconnectivity with frontal areas, the autism group showed no underconnectivity among posterior cortical regions. These results extend previous findings of abnormal face perception in autism by demonstrating that the abnormalities are embedded in an abnormal cortical network that manages to perform the working memory task proficiently, using a visually oriented, asocial processing style that minimizes reliance on prefrontal areas.

Understanding autism and related disorders: what has imaging taught us?

Structural imaging studies of autism have documented increased total brain volume and early acceleration in brain growth. Functional MR imaging (fMRI) studies in autism have also led to the view of autism as a disorder of cortical functioning in which functional connectivity or synchronization of brain regions and cortical activity are disturbed with atypical cortical specialization.

Abnormal functional connectivity in autism spectrum disorders during face processing

Abnormalities in the interactions between functionally linked brain regions have been suggested to be associated with the clinical impairments observed in autism spectrum disorders (ASD). We investigated functional connectivity within the limbic system during face identification; a primary component of social cognition, in 19 high-functioning adults with ASD and 21 age-and IQ-matched control adults. Activation during identification of previously viewed faces and houses using a one-back paradigm was compared. The fusiform face area (FFA) was individually localized in each participant and used as the seed point for functional connectivity analyses. The degree of correlation between FFA and the extended neural circuitry involved in face identification was tested. A whole brain analysis was also conducted in order to determine whether connectivity from the FFA to aberrant brain locations was present in the ASD group. Measures of clinical severity (ADOS social score and ADI-R social score) were included as independent variables into the functional connectivity analyses. Significant FFA-amygdala and FFA-superior temporal sulcus functional connectivity was found in both the ASD and control participants. However, the control group had significantly increased connectivity to the left amygdala and the posterior cingulate compared to ASD. Post hoc analyses additionally found increased connectivity to the thalamus in the controls. A significant relationship between abnormal functional connectivity and clinical severity in the ASD group was observed. Specifically, greater social impairment was associated with reduced FFA-amygdala connectivity and increased FFA-right inferior frontal connectivity. These results suggest that abnormal neural connections within the limbic system may contribute to the social impairments observed in ASD.

Fronto-limbic functioning in children and adolescents with and without autism

We used neuropsychological tasks to investigate integrity of brain circuits linking orbitofrontal cortex and amygdala (orbitofrontal-amygdala), and dorsolateral prefrontal cortex and hippocampus (dorsolateral prefrontal-hippocampus), in 138 individuals aged 7-18 years, with and without autism. We predicted that performance on orbitofrontal-amygdala tasks would be poorer in the Autism group compared to the Non-Autism group regardless of intellectual level (verbal mental age, VMA) and that performance on dorsolateral prefrontal-hippocampus tasks would be associated primarily with intellectual level. Predicted differences between Autism and Non-Autism groups on orbitofrontal-amygdala tasks were present but greater in individuals with higher VMA. On dorsolateral prefrontal-hippocampus tasks, poorer performance by the Autism compared to the Non-Autism group was found at all VMA levels. Group differences suggest both brain circuits are impaired in autism, but performance on all tasks is also associated with intellectual level.

Abnormal adaptive face-coding mechanisms in children with autism spectrum disorder

In low-level vision, exquisite sensitivity to variation in luminance is achieved by adaptive mechanisms that adjust neural sensitivity to the prevailing luminance level. In high-level vision, adaptive mechanisms contribute to our remarkable ability to distinguish thousands of similar faces [1]. A clear example of this sort of adaptive coding is the face-identity aftereffect [2, 3, 4, 5], in which adaptation to a particular face biases perception toward the opposite identity. Here we investigated face adaptation in children with autism spectrum disorder (ASD) by asking them to discriminate between two face identities, with and without prior adaptation to opposite-identity faces. The ASD group discriminated the identities with the same precision as did the age- and ability-matched control group, showing that face identification per se was unimpaired. However, children with ASD showed significantly less adaptation than did their typical peers, with the amount of adaptation correlating significantly with current symptomatology, and face aftereffects of children with elevated symptoms only one third those of controls. These results show that although children with ASD can learn a simple discrimination between two identities, adaptive face-coding mechanisms are severely compromised, offering a new explanation for previously reported face-perception difficulties [6, 7, 8] and possibly for some of the core social deficits in ASD [9, 10].

Neurogenesis in the amygdala: A new etiologic hypothesis of autism?

Neurogenesis studies had an increased development after BrdU (5-bromo-3'-deoxyuridine), a marker of cell proliferation. Today, several studies have showed the relevance of neurogenesis in the hippocampal formation. Notwithstanding, other brains areas have been described presenting neurogenesis, including the amygdala. This key structure is a complex cerebral region which has been associated with social behaviors and the emotional significance of the daily experiences. Several studies have associated the amygdala to the autism, a severe neurodevelopmental disorder. In this paper, we discuss the hypothesis of neurogenesis in the amygdala as a contributing cause of autism. The social skills require competent new neuronal connections, including efficient plasticity synaptic rearranging. Interestingly, emotional context cannot be imprinting in mature neurons in the presence of GABA, a neurotransmitter release during new environments experiences. However, it is known that new neurons are not well responsive to GABA stimulation, allowing the long-term potentiation necessary for the learning process. Based on these evidence it is tantalizing to hypothesize that the sociability impairment seen in some individuals with autism may partly be assigned to impaired regulation of the GABAergic system and to the impact of this impairment on the adequate functioning of the amygdala and on its capacity to store new experiences and to modulate the plasticity of the corticostriatal connections.

Bayesian analysis of fMRI data with ICA based spatial prior

Spatial modeling is essential for fMRI analysis due to relatively high noise in the data. Earlier approaches have been primarily concerned with the spatial coherence of the BOLD response in local neighborhoods. In addition to a smoothness constraint, we propose to incorporate prior knowledge of brain activation patterns learned from training samples. This spatially informed prior can significantly enhance the estimation process by inducing sensitivity to task related regions of the brain. As fMRI data exhibits intersubject variability in functional anatomy, we design the prior using Independent Component Analysis (ICA). Due to the non-Gaussian assumption, ICA does not regress to the mean activation pattern and thus avoids suppressing intersubject differences. Results from a real fMRI experiment indicate that our approach provides statistically significant improvement in estimating activation compared to the standard general linear model (GLM) based methods.

Intact emotion facilitation for nonsocial stimuli in autism: is amygdala impairment in autism specific for social information?

Atypical amygdala development may play a key role in the emergence of social disability and other symptoms of autism (Baron-Cohen et al., 2000; Schultz, 2005). The mechanisms by which this may occur have received little attention, however, and most support from behavioral and imaging studies has been concerned with socially relevant stimuli such as faces. Given the complexity of amygdala function and its known role in many other emotional tasks, we examined whether individuals with autism would demonstrate impaired performance on several tasks that have been shown to require activation of the amygdala but that do not have any explicit social meaning. Relative to a typical comparison group matched for age and IQ, our sample of 37 adolescents and adults with autism (mean age=19.7 years) demonstrated equivalent facilitation for perception and learning of emotionally relevant stimuli. On each of four tasks, there were significant main effects of emotion condition on performance for both groups. Future research regarding atypical amygdala function and emotion processing in autism should consider whether the response to nonsocial emotion factors (including negative valence or high arousal) may be intact, despite difficulties in responding to socially relevant stimuli.

Specific components of face perception in the human fusiform gyrus studied by tomographic estimates of magnetoencephalographic signals: a tool for the evaluation of non-verbal communication in psychosomatic paradigms

Aims

The aim of this study was to determine the specific spatiotemporal activation patterns of face perception in the fusiform gyrus (FG). The FG is a key area in the specialized brain system that makes possible the recognition of face with ease and speed in our daily life. Characterization of FG response provides a quantitative method for evaluating the fundamental functions that contribute to non-verbal communication in various psychosomatic paradigms.

Methods

The MEG signal was recorded during passive visual stimulus presentation with three stimulus types – Faces, Hands and Shoes. The stimuli were presented separately to the central and peripheral visual fields. We performed statistical parametric mapping (SPM) analysis of tomographic estimates of activity to compare activity between a pre- and post-stimulus period in the same object (baseline test), and activity between objects (active test). The time course of regional activation curves was analyzed for each stimulus condition.

Results

The SPM baseline test revealed a response to each stimulus type, which was very compact at the initial segment of main M_FG170. For hands and shoes the area of significant change remains compact. For faces the area expanded widely within a few milliseconds and its boundaries engulfed the other object areas. The active test demonstrated that activity for faces was significantly larger than the activity for hands. The same face specific compact area as in the baseline test was identified, and then again expanded widely. For each stimulus type and presentation in each one of the visual fields locations, the analysis of the time course of FG activity identified three components in the FG: M_FG100, M_FG170, and M_FG200 – all showed preference for faces.

Conclusion

Early compact face-specific activity in the FG expands widely along the occipito-ventral brain within a few milliseconds. The significant difference between faces and the other object stimuli in M_FG100 shows that processing of faces is already differentiated from processing of other objects within 100 ms. Standardization of the three face-specific MEG components could have diagnostic value for the integrity of the initial process of non-verbal communication in various psychosomatic paradigms.

Emotional modulation of perception in Asperger's syndrome

Using an attentional blink paradigm, we show that the typical enhancement of perception for emotionally arousing events is significantly reduced in Asperger's syndrome (AS) at short inter-target intervals. Control experiments demonstrate that this finding cannot be attributed to differences in the perceived arousal of the stimuli, or to a global impairment affecting any type of modulation of perceptual encoding. Because a functioning amygdala is critical for emotional modulation of the attentional blink, the findings support a role for the amygdala in the pathophysiology of AS. More specifically, they suggest there is a fundamental failure of the amygdala to modulate processing in cortex, a concept at the heart of some recent theories of amygdala involvement in the aetiology of autistic-spectrum disorders.

Abnormal magnocellular pathway visual processing in infants at risk for autism

BACKGROUND

A wealth of data has documented impairments in face processing in individuals with autism spectrum disorders (ASD). Recently, the suggestion has been made that these impairments may arise from abnormal development of a subcortical system involved in face processing that originates in the magnocellular pathway of the primate visual system.

METHODS

To test this developmental hypothesis, we obtained visual perceptual data from 6-month-old infants who were at risk for ASD because they had an older sibling diagnosed with the disorder ("high-risk infants"). To measure sensitivity of the magnocellular (M) pathway and, for comparison, of the parvocellular (P) visual pathway, we employed visual stimuli designed to selectively stimulate the two. Sensitivity data from high-risk infants (n = 13) were compared with data from matched control infants (i.e., "low-risk" infants with no family history of ASD, n = 26).

RESULTS

On the P pathway stimulus, high-risk infants exhibited sensitivities that were identical to those of control infants. By contrast, on the M pathway stimulus, high-risk infants exhibited sensitivities nearly twofold greater than those of control infants.

CONCLUSIONS

Given that ASD and its symptoms are known to run in families, these preliminary results suggest that ASD may be associated with abnormal M pathway function early in infancy, which may aid in early diagnosis of the disorder.

Identification and evaluation of children with autism spectrum disorders

Autism spectrum disorders are not rare; many primary care pediatricians care for several children with autism spectrum disorders. Pediatricians play an important role in early recognition of autism spectrum disorders, because they usually are the first point of contact for parents. Parents are now much more aware of the early signs of autism spectrum disorders because of frequent coverage in the media; if their child demonstrates any of the published signs, they will most likely raise their concerns to their child's pediatrician. It is important that pediatricians be able to recognize the signs and symptoms of autism spectrum disorders and have a strategy for assessing them systematically. Pediatricians also must be aware of local resources that can assist in making a definitive diagnosis of, and in managing, autism spectrum disorders. The pediatrician must be familiar with developmental, educational, and community resources as well as medical subspecialty clinics. This clinical report is 1 of 2 documents that replace the original American Academy of Pediatrics policy statement and technical report published in 2001. This report addresses background information, including definition, history, epidemiology, diagnostic criteria, early signs, neuropathologic aspects, and etiologic possibilities in autism spectrum disorders. In addition, this report provides an algorithm to help the pediatrician develop a strategy for early identification of children with autism spectrum disorders. The accompanying clinical report addresses the management of children with autism spectrum disorders and follows this report on page 1162 [available at www.pediatrics.org/cgi/content/full/120/5/1162]. Both clinical reports are complemented by the toolkit titled "Autism: Caring for Children With Autism Spectrum Disorders: A Resource Toolkit for Clinicians," which contains screening and surveillance tools, practical forms, tables, and parent handouts to assist the pediatrician in the identification, evaluation, and management of autism spectrum disorders in children.

The intense world syndrome--an alternative hypothesis for autism

Autism is a devastating neurodevelopmental disorder with a polygenetic predisposition that seems to be triggered by multiple environmental factors during embryonic and/or early postnatal life. While significant advances have been made in identifying the neuronal structures and cells affected, a unifying theory that could explain the manifold autistic symptoms has still not emerged. Based on recent synaptic, cellular, molecular, microcircuit, and behavioral results obtained with the valproic acid (VPA) rat model of autism, we propose here a unifying hypothesis where the core pathology of the autistic brain is hyper-reactivity and hyper-plasticity of local neuronal circuits. Such excessive neuronal processing in circumscribed circuits is suggested to lead to hyper-perception, hyper-attention, and hyper-memory, which may lie at the heart of most autistic symptoms. In this view, the autistic spectrum are disorders of hyper-functionality, which turns debilitating, as opposed to disorders of hypo-functionality, as is often assumed. We discuss how excessive neuronal processing may render the world painfully intense when the neocortex is affected and even aversive when the amygdala is affected, leading to social and environmental withdrawal. Excessive neuronal learning is also hypothesized to rapidly lock down the individual into a small repertoire of secure behavioral routines that are obsessively repeated. We further discuss the key autistic neuropathologies and several of the main theories of autism and re-interpret them in the light of the hypothesized Intense World Syndrome.

Autism and the amygdala: An endocrine hypothesis

Children become oriented to the world, in part, by coming to understand something of the experiences of others. The facial expressions that people make are an avenue for understanding something about them, as are the diverse forms of bodily responses emitted and interpreted by individuals. People with autism often find bodily communications to be aversive, thereby limiting what they can learn from others during social interactions. The amygdala is an important area of the brain, amongst others, for integrating the internal milieu with the social ambiance. Individuals with autism consistently demonstrate dysregulation of amygdala function. Diverse regions of the amygdala, which contain neuropeptides, figure in the appraisal systems that underlie behavioral approach and avoidance responses. One neuropeptide linked to social recognition and approach behaviors is oxytocin (which is known to be decreased in autistic individuals) and another neuropeptide corticotropin releasing hormone is tied to avoidance behaviors. A neuroendocrine hypothesis is suggested to account for some of the features associated with autism.

Avoidance of emotionally arousing stimuli predicts social-perceptual impairment in Asperger's syndrome

We combined eye-tracking technology with a test of facial affect recognition and a measure of self-reported social anxiety in order to explore the aetiology of social-perceptual deficits in Asperger's syndrome (AS). Compared to controls matched for age, IQ and visual-perceptual ability, we found a group of AS adults was impaired in their recognition of fearful and sad expressions and spent significantly less time fixating the eye region of all faces. For AS subjects, but not controls, the extent of the failure to fixate the eyes predicted the degree of impairment at recognising fearful expressions. In addition, poor fear recognition and reduced fixation of the eyes were independently associated with greater levels of social anxiety in AS individuals. These findings support the hypothesis that avoidance of emotionally arousing stimuli, such as eyes, contributes to social-perceptual impairment in AS. Furthermore, our findings are consistent with theories implicating amygdala-mediated over-arousal and anxiety in the development of these social-perceptual deficits.

Parent-Rated Anxiety Symptoms in Children with Pervasive Developmental Disorders: Frequency and Association with Core Autism Symptoms and Cognitive Functioning

BACKGROUND

In addition to the core symptoms, children with Pervasive Developmental Disorders (PDD) often exhibit other problem behaviors such as aggression, hyperactivity, and anxiety, which can contribute to overall impairment and, therefore, become the focus of clinical attention. Limited data are available on the prevalence of anxiety in these children. We examined frequency and correlates of parent-rated anxiety symptoms in a large sample of children with PDD.

METHODS

The goals of this study were to examine the frequency and correlates of parent-rated anxiety symptoms in a sample of 171 medication-free children with PDD who participated in two NIH-funded medication trials. Twenty items of the Child and Adolescent Symptom Inventory (CASI) were used to measure anxiety.

RESULTS

Forty three percent of the total sample met screening cut-off criteria for at least one anxiety disorder. Higher levels of anxiety on the 20-item CASI scale were associated with higher IQ, the presence of functional language use, and with higher levels of stereotyped behaviors. In children with higher IQ, anxiety was also associated with greater impairment in social reciprocity.

CONCLUSION

Anxiety is common in PDD and warrants consideration in clinical evaluation and treatment planning. This study suggests that parent ratings could be a useful source of information about anxiety symptoms in this population. Some anxiety symptoms such as phobic and social anxiety may be closer to core symptoms of PDD. Further efforts to validate tools to ascertain anxiety are needed, as are studies to empirically test approaches to treat anxiety in PDD.

An event related functional magnetic resonance imaging study of facial emotion processing in Asperger syndrome

BACKGROUND

People with Asperger syndrome (AS) have life-long deficits in social behavior. The biological basis of this is unknown, but most likely includes impaired processing of facial emotion. Human social communication involves processing different facial emotions, and at different intensities. However nobody has examined brain function in people with AS when implicitly (unconsciously) processing four primary emotions at varying emotional intensities.

METHODS

We used event-related functional magnetic resonance imaging (MRI) to examine neural responses when people with AS and controls implicitly processed neutral expressions, and mild (25%) and intense (100%) expressions of fear, disgust, happiness, and sadness. We included 18 right-handed adults; 9 with AS and 9 healthy controls who did not differ significantly in IQ.

RESULTS

Both groups significantly activated 'face perception' areas when viewing neutral faces, including fusiform and extrastriate cortices. Further, both groups had significantly increased activation of fusiform and other extrastriate regions to increasing intensities of fear and happiness. However, people with AS generally showed fusiform and extrastriate hyporesponsiveness compared to controls across emotion types and intensities.

CONCLUSIONS

Fusiform and extrastriate cortices are activated by facial expressions of four primary emotions in people with AS, but generally to a lesser degree than controls. This may partly explain the social impairments of people with AS.

Event schemas in autism spectrum disorders: the role of theory of mind and weak central coherence

Event schemas (generalized knowledge of what happens at common real-life events, e.g., a birthday party) are an important cognitive tool for social understanding: They provide structure for social experiences while accounting for many variable aspects. Using an event narratives task, this study tested the hypotheses that theory of mind (ToM) deficits and weak central coherence (WCC, a local processing bias) undermine different aspects of event knowledge in people with autism spectrum disorder (ASD). Event narratives of ASD ToM-failers were overall significantly impaired. ASD ToM-passers showed more specific abnormalities relating to variable activities, and some of these were significantly associated to WCC. Abnormalities in event knowledge might help linking ASD-typical social deficits in real-life situations and the adherence to inflexible routines.

Quantitative temporal lobe differences: autism distinguished from controls using classification and regression tree analysis

The temporal lobe is thought to be abnormal in autism, yet standard volumetric analyses are often unrevealing when age, sex, IQ, and head size are controlled. Quantification of temporal lobe structures were obtained in male subjects with autism and controls, where subjects with head circumference (HC) defined macrocephaly were excluded, so that volume differences were not just related to the higher prevalence of macrocephaly in autism. Various statistical methods were applied to the analysis including a classification and regression tree (CART) method, a non-parametric technique that helps define patterns of relationships that may be meaningful in distinguishing temporal lobe differences between subjects with autism and age and IQ matched controls. Subjects with autism were also compared to a separate control group with reading disorder (RD), with the prediction that the temporal lobe morphometric analysis of the reading disorder controls would be more similar to that of the autism group. The CART method yielded a high specificity in classifying autism subjects from controls based on the relationship between the volume of the left fusiform gyrus (LFG) gray and white matter, the right temporal stem (RTS) and the right inferior temporal gyrus gray matter (RITG-GM). Reading disordered individuals were more similar to subjects with autism. Simple size differences did not distinguish the groups. These findings demonstrate different relationships within temporal lobe structures that distinguish subjects with autism from controls. Results are discussed in terms of pathological connectivity within the temporal lobe as it relates to autism.

Face processing in Pervasive Developmental Disorder (PDD): the roles of expertise and spatial frequency

Both a reduced face expertise and a basic abnormality in visual information, e.g. spatial frequency, processing have been proposed as possible causes of the abnormal face processing in Pervasive Developmental Disorder (PDD). This study investigated both the roles of expertise and spatial frequency for face processing in PDD. Event-related potentials (ERPs) and dipole sources were measured in response to (upright/inverted) high- and low-pass filtered faces, houses, and stimuli for which children with PDD were experts. ERP analyses for specific posterior electrodes showed no differences between children with PDD and matched controls, but source analyses did. These showed that controls activated specialized brain sources for the processing of faces, which was dependent on low spatial frequency content. However, children with PDD did not. Importantly, present results argue against the idea that this is due to a reduced face expertise on the part of the children with PDD, but instead support an abnormality in spatial frequency processing.

Backward masking: evidence of reduced subcortical amygdala engagement in autism

Recent data suggest that subthreshold presentation of emotional information is relayed to the amygdala along subcortical pathways. We examined the effect of backward masked neutral and anxious faces on the social decisions of a group of high functioning children with autism ages 7-13 years and matched controls. Participants were asked to select the friendliest of two faces, one of which was associated with the subthreshold (33 ms) presentation of an anxious face (A/N) and the other a subthreshold neutral face (N/N). Neutral paired faces were selected more often than A/N paired faces by both groups. However, children with autism selected significantly fewer N/N stimuli and more A/N stimuli than controls. These results suggest that the social choices of children with autism were influenced less by emotional information presented subconsciously and suggest a subcortical contribution to the social/emotional processing deficits observed in autism.

The application of eye-tracking technology in the study of autism

For many decades, eye-tracking has been used to investigate gaze behaviour in the normal population. Recent studies have extended its use to individuals with disorders on the autism spectrum. Such studies typically focus on the processing of socially salient stimuli. In this review, we discuss the potential for this technique to reveal the strategies adopted by individuals with high-functioning autism when processing social information. Studies suggest that eye-tracking techniques have the potential to offer insight into the downstream difficulties in everyday social interaction which such individuals experience.

Lateral glances toward moving stimuli among young children with autism: Early regulation of locally oriented perception?

Autistic adults display enhanced and locally oriented low-level perception of static visual information, but diminished perception of some types of movement. The identification of potential precursors, such as atypical perceptual processing, among very young children would be an initial step toward understanding the development of these phenomena. The purpose of this study was to provide an initial measure and interpretation of atypical visual exploratory behaviors toward inanimate objects (AVEBIOs) among young children with autism. A coding system for AVEBIOs was constructed from a corpus of 40 semistandardized assessments of autistic children. The most frequent atypical visual behavior among 15 children aged 33-73 months was lateral glance that was mostly oriented toward moving stimuli and was detected reliably by the experimenters (intraclass correlation > .90). This behavior was more common among autistic than typically developing children of similar verbal mental age and chronological age. As lateral vision is associated with the filtering of high spatial frequency (detail perception) information and the facilitation of high temporal frequencies (movement perception), its high prevalence among very young autistic children may reflect early attempts to regulate and/or optimize both excessive amounts of local information and diminished perception of movement. These findings are initial evidence for the need to consider the neural bases and development of atypical behaviors and their implications for intervention strategies.

Perception of dynamic changes in facial affect and identity in autism

Despite elegant behavioral descriptions of abnormalities for processing emotional facial expressions and biological motion in autism, identification of the neural mechanisms underlying these abnormalities remains a critical and largely unmet challenge. We compared brain activity with dynamic and static facial expressions in participants with and without high-functioning autism using event-related functional magnetic resonance imaging (fMRI) and three classes of face stimuli-emotion morphs (fearful and angry), identity morphs and static images (fearful, angry and neutral). We observed reduced activity in the amygdala (AMY) and fusiform gyrus (FFG) to dynamic emotional expressions in people with autism. There was also a lack of modulation by dynamic compared with static emotional expressions of social brain regions including the AMY, posterior superior temporal sulcus (STS) region and FFG. We observed equivalent emotion and identity morph-evoked activity in participants with and without autism in a region corresponding to the expected location of the more generally motion-sensitive area MT or V5. We conclude that dysfunctions in key components of the human face processing system including the AMY, FFG and posterior STS region are present in individuals with high-functioning autism, and this dysfunction might contribute to the deficits in processing emotional facial expressions.

Impaired sadness recognition is linked to social interaction deficit in autism

Can autistic individuals use motion cues to identify simple emotions from 2D abstract animations? We compared emotion recognition ability using a novel test involving computerised animations, and a more conventional emotion recognition test using facial expressions. Adults with autism and normal controls, matched for age and verbal IQ, participated in two experiments. First, participants viewed a series of short (5s) animations. These featured an 'emotional' triangle, interacting with a circle. They were designed to evoke an attribution of emotion to the triangle, which was rated both in terms of anger, happiness, sadness or fear from its pattern of movement, and how animate ("living") it appeared to be. Second, emotion recognition was tested from standardised photographs of facial expressions. In both experiments, adults with autism were significantly impaired relative to comparisons in their perception of sadness. This is the first demonstration that, in autism, individuals can have difficulties both in the interpretation of facial expressions and in the recognition of equivalent emotions based on the movement of abstract stimuli. Poor performance in the animations task was significantly correlated with the degree of impairment in reciprocal social interaction, assessed by the Autism Diagnostic Observation Schedule. Our findings point to a deficit in emotion recognition in autism, extending beyond the recognition of facial expressions, which is associated with a functional impairment in social interaction skills. Our results are discussed in the context of the results of neuroimaging studies that have used animated stimuli and images of faces.

Neurodevelopmental and behavioral issues in Williams syndrome

Much existing research on Williams syndrome (WS) has focused on the individuals' unusual cognitive profile, with less emphasis placed on the developmental and neural underpinnings of the disorder. We review recent findings from brain imaging and begin to discuss links from these data to the behavioral phenotype. Overall brain size is significantly reduced in individuals with WS, as it is in many mental retardation syndromes. However, the specific profile of deficits in WS, particularly the visuospatial deficits, appears to be linked to parietal lobe abnormalities. Results from both genetic and brain imaging studies have provided useful insights into WS neurobiology. However, future work needs to remediate the lack of studies investigating developmental processes.

A fine-grained analysis of facial expression processing in high-functioning adults with autism

It is unclear whether individuals with autism are impaired at recognizing basic facial expressions, and whether, if any impairment exists, it applies to expression processing in general, or to certain expressions, in particular. To evaluate these alternatives, we adopted a fine-grained analysis of facial expression processing in autism. Specifically, we used the 'facial expression megamix' paradigm [Young, A. W., Rowland, D., Calder, A. J, Etcoff, N. L., Seth, A., & Perrett, D. I. (1997). Facial expression megamix: Tests of dimensional and category accounts of emotion recognition Cognition and Emotion, 14, 39-60] in which adults with autism and a typically developing comparison group performed a six alternative forced-choice response to morphs of all possible combinations of the six basic expressions identified by Ekman [Ekman, P. (1972). Universals and cultural differences in facial expressions of emotion. In J. K. Cole (Ed.), Nebraska symposium on motivation: vol. 1971, (pp. 207-283). Lincoln, Nebraska: University of Nebraska Press] (happiness, sadness, disgust, anger, fear and surprise). Clear differences were evident between the two groups, most obviously in the recognition of fear, but also in the recognition of disgust and happiness. A second experiment demonstrated that individuals with autism are able to discriminate between different emotional images and suggests that low-level perceptual difficulties do not underlie the difficulties with emotion recognition.

Impairments in monkey and human face recognition in 2-year-old toddlers with Autism Spectrum Disorder and Developmental Delay

Face recognition impairments are well documented in older children with Autism Spectrum Disorders (ASD); however, the developmental course of the deficit is not clear. This study investigates the progressive specialization of face recognition skills in children with and without ASD. Experiment 1 examines human and monkey face recognition in 2-year-old children with ASD, matched for nonverbal mental age (NVMA) with developmentally delayed (DD) children, and typically developing children (TD), using the Visual Paired Comparison (VPC) paradigm. Results indicate that, consistent with the other-species effect, TD controls show enhanced recognition of human but not monkey faces; however, neither the ASD nor the DD group show evidence of face recognition regardless of the species. Experiment 2 examines the same question in a group of older 3- to 4-year-old developmentally disabled (ASD and DD) children as well as in typical controls. In this experiment, both human and monkey faces are recognized by all three groups. The results of Experiments 1 and 2 suggest that difficulties in face processing, as measured by the VPC paradigm, are common in toddlers with ASD as well as DD, but that these deficits tend to disappear by early preschool age. In addition, the experiments show that higher efficacy of incidental encoding and recognition of facial identity in a context of passive exposure is positively related to nonverbal cognitive skills and age, but not to overall social interaction skills or greater attention to faces exhibited in naturalistic contexts.

Neurophysiological responses to face, facial regions and objects in adults with Asperger's syndrome: An ERP investigation

Face processing differences have been observed between AS and control subjects at the behavioural and neurological levels. The purpose of the present study was to investigate the neurophysiological basis of processing faces and facial features (eyes and mouths) in adults with AS relative to age- and gender-matched typically-developing controls. These results were compared with ERPs generated to objects in both groups to determine if any differences were specific to facial stimuli. Although both groups elicited earlier N170 latencies to faces than to face parts and to eyes relative to mouths, adults with AS exhibited delayed N170 latencies to faces and face parts relative to controls. This difference was not observed to objects. Together these findings suggest that adults with AS may be slower to process facial information.

Brain basis of early parent-infant interactions: psychology, physiology, and in vivo functional neuroimaging studies

Parenting behavior critically shapes human infants' current and future behavior. The parent-infant relationship provides infants with their first social experiences, forming templates of what they can expect from others and how to best meet others' expectations. In this review, we focus on the neurobiology of parenting behavior, including our own functional magnetic resonance imaging (fMRI) brain imaging experiments of parents. We begin with a discussion of background, perspectives and caveats for considering the neurobiology of parent-infant relationships. Then, we discuss aspects of the psychology of parenting that are significantly motivating some of the more basic neuroscience research. Following that, we discuss some of the neurohormones that are important for the regulation of social bonding, and the dysregulation of parenting with cocaine abuse. Then, we review the brain circuitry underlying parenting, proceeding from relevant rodent and nonhuman primate research to human work. Finally, we focus on a study-by-study review of functional neuroimaging studies in humans. Taken together, this research suggests that networks of highly conserved hypothalamic-midbrain-limbic-paralimbic-cortical circuits act in concert to support aspects of parent response to infants, including the emotion, attention, motivation, empathy, decision-making and other thinking that are required to navigate the complexities of parenting. Specifically, infant stimuli activate basal forebrain regions, which regulate brain circuits that handle specific nurturing and caregiving responses and activate the brain's more general circuitry for handling emotions, motivation, attention, and empathy--all of which are crucial for effective parenting. We argue that an integrated understanding of the brain basis of parenting has profound implications for mental health.

Do individuals with autism process categories differently? The effect of typicality and development

This study examined the effect of exemplar typicality on reaction time and accuracy of categorization. High-functioning children (age 9-12), adolescents (age 13-16), and adults with autism (age 17-48) and matched controls were tested in a category verification procedure. All groups showed improved processing throughout the lifespan for typical and somewhat typical category exemplars. However, individuals with autism responded more slowly than matched controls to atypical exemplars at all ages. The results are discussed in terms of potential differences in the type of processing that may be required for categorizing typical and atypical category exemplars. Parallels are also drawn to the results of previous studies on face processing in individuals with autism.

Genetic influences on the neural basis of social cognition

The neural basis of social cognition has been the subject of intensive research in both human and non-human primates. Exciting, provocative and yet consistent findings are emerging. A major focus of interest is the role of efferent and afferent connectivity between the amygdala and the neocortical brain regions, now believed to be critical for the processing of social and emotional perceptions. One possible component is a subcortical neural pathway, which permits rapid and preconscious processing of potentially threatening stimuli, and it leads from the retina to the superior colliculus, to the pulvinar nucleus of the thalamus and then to the amygdala. This pathway is activated by direct eye contact, one of many classes of potential threat, and may be particularly responsive to the 'whites of the eyes'. In humans, autonomic arousal evoked by this stimulus is associated with the activity in specific cortical regions concerned with processing visual information from faces. The integrated functioning of these pathways is modulated by one or more X-linked genes, yet to be identified. The emotional responsiveness of the amygdala, and its associated circuits, to social threat is also influenced by functional polymorphisms in the promoter of the serotonin transporter gene. We still do not have a clear account of how specific allelic variation, in candidate genes, increases susceptibility to developmental disorders, such as autism, or psychiatric conditions, such as anxiety or depressive illness. However, the regulation of emotional responsiveness to social cues lies at the heart of the problem, and recent research indicates that we may be nearing a deeper and more comprehensive understanding.

Face- and gaze-sensitive neural responses in children with autism: a magnetoencephalographic study

Face and gaze processing were studied using magnetoencephalography in 10 children with autism and 10 normally developing children, aged between 7 and 12 years. The children performed two tasks in which they had to discriminate whether images of faces presented sequentially in pairs were identical. The images showed four different categories of gaze: direct gaze, eyes averted (left or right) and closed eyes but there was no instruction to focus on the direction of gaze. Images of motorbikes were used as control stimuli. Faces evoked strong activity over posterior brain regions at about 100 ms in both groups of children. A response at 140 ms to faces observed over extrastriate cortices, thought to be homologous to the N170 in adults, was weak and bilateral in both groups and somewhat weaker (approaching significance) in the children with autism than in the control children. The response to motorbikes differed between the groups at 100 and 140 ms. Averted eyes evoked a strong right lateralized component at 240 ms in the normally developing children that was weak in the clinical group. By contrast, direct gaze evoked a left lateralized component at 240 ms only in children with autism. The findings suggest that face and gaze processing in children with autism follows a trajectory somewhat similar to that seen in normal development but with subtle differences. There is also a possibility that other categories of object may be processed in an unusual way. The inter-relationships between these findings remain to be elucidated.

Mouse behavioral tasks relevant to autism: phenotypes of 10 inbred strains

Three defining clinical symptoms of autism are aberrant reciprocal social interactions, deficits in social communication, and repetitive behaviors, including motor stereotypies and insistence on sameness. We developed a set of behavioral tasks designed to model components of these core symptoms in mice. Male mice from 10 inbred strains were characterized in assays for sociability, preference for social novelty, and reversal of the spatial location of the reinforcer in T-maze and Morris water maze tasks. Six strains, C57BL/6J, C57L/J, DBA/2J, FVB/NJ, C3H/HeJ, and AKR/J, showed significant levels of sociability, while A/J, BALB/cByJ, BTBR T(+)tf/J, and 129S1/SvImJ mice did not. C57BL/6J, C57L/J, DBA/2J, FVB/NJ, BALB/cByJ, and BTBR T(+)tf/J showed significant preference for social novelty, while C3H/HeJ, AKR/J, A/J, and 129S1/SvImJ did not. Normal scores on relevant control measures confirmed general health and physical abilities in all strains, ruling out artifactual explanations for social deficits. Elevated plus maze scores confirmed high anxiety-like behaviors in A/J, BALB/cByJ, and 129S1/SvImJ, which could underlie components of their low social approach. Strains that showed high levels of performance on acquisition of a T-maze task were also able to reach criterion for reversal learning. On the Morris water maze task, DBA/2J, AKR/J, BTBR T(+)tf/J, and 129S1/SvImJ failed to show significant quadrant preference during the reversal probe trial. These results highlight a dissociation between social task performance and reversal learning. BTBR T(+)tf/J is a particularly interesting strain, displaying both low social approach and resistance to change in routine on the water maze, consistent with an autism-like phenotype. Our multitask strategy for modeling symptoms of autism will be useful for investigating targeted and random gene mutations, QTLs, and microarray analyses.

Colony formation of C57BL/6J mice in visible burrow system: identification of eusocial behaviors in a background strain for genetic animal models of autism

Deficits in social interaction are primary characteristics of autism, which has strong genetic components. Genetically manipulated mouse models may provide a useful research tool to advance the investigation of genes associated with autism. To identify these genes using mouse models, behavioral assays for social relationships in the background strains must be developed. The present study examined colony formation in groups of one male and three female mice (Experiment 1) and, groups of three male mice (Experiment 2) of the C57BL/6J strain in a semi-natural visible burrow system. For adult mixed-sex colonies, 4-h observations during both the dark and light cycles for 15 days demonstrated day-dependent increases in huddling together in the chamber accompanied by decreased frequencies of active social behaviors. Sequential analyses of social interactions indicated that approaches to the back of the approached animal typically elicited flight, while approaches to the front of the approached animal failed to do so. This was seen for female to female, and for female to male approaches, as well as male to female approaches, strongly counterindicating a view that rear approach/flight specifically reflects female responsivirity to unwanted male sexual approach. For adult male colonies, similar protocols found that these social behaviors were similar to those of adult mixed-sex colonies. These findings suggest two potentially useful measures of eusocial behavior in mice, of possible value for genetic mouse models of autism; that is, huddling together and approaches to the front but not the back, of conspecifics.

Visual Fixation Patterns during Reciprocal Social Interaction Distinguish a Subgroup of 6-Month-Old Infants At-Risk for Autism from Comparison Infants

Thirty-one infant siblings of children with autism and 24 comparison infants were tested at 6 months of age during social interaction with a caregiver, using a modified Still Face paradigm conducted via a closed-circuit TV-video system. In the Still Face paradigm, the mother interacts with the infant, then freezes and displays a neutral, expressionless face, then resumes interaction. Eye tracking data on infant visual fixation patterns were recorded during the three episodes of the experiment. Using a hierarchical cluster analysis, we identified a subgroup of infants demonstrating diminished gaze to the mother's eyes relative to her mouth during the Still Face episode. Ten out of the 11 infants in this subgroup had an older sibling with autism.

Identification of EFHC2 as a quantitative trait locus for fear recognition in Turner syndrome

One-third of women with Turner syndrome (45,X) have autism-like social and communication difficulties, despite normal verbal IQ. Deletion mapping of the X-chromosome implicated 5 Mb of Xp11.3-4 as critical for recognition of facial fear, a quantitative measure of social cognition. Variability in fear recognition accuracy in Turner syndrome suggested the existence of a quantitative trait locus (QTL) revealed by X-monosomy. We aimed to identify the gene(s) influencing fear recognition by dense mapping of the 5 Mb region. Initial regression-based association mapping of fear recognition in 93 women with Turner syndrome across the critical region was performed, using genotype data at 242 single nucleotide polymorphisms (SNPs). We identified three regions of interest, in which 52 additional SNPs were genotyped. The third region then contained four SNPs associated with fear recognition (0.0030 > P > 0.00046). We obtained an independent sample of 77 Turner syndrome females that we genotyped for 77 SNPs in the initial regions of interest. Region three showed association in the same direction, maximal at SNPs rs7055196 and rs7887763 (P = 0.022 each). Four SNPs in strong linkage disequilibrium (LD), including this pair, span 40 kb within a novel transcript, EF-hand domain containing 2 (EFHC2). In the combined Turner syndrome samples, the most strongly associated SNP (P = 0.00007) has frequency of 8.8% and an estimated effect size accounting for over 13% of the variance in fear recognition. EFHC2 shows genealogy and extended LD consistent with directional selection. This novel QTL may influence social cognition in the general population and in autism.

Looking you in the mouth: abnormal gaze in autism resulting from impaired top-down modulation of visual attention

People with autism are impaired in their social behavior, including their eye contact with others, but the processes that underlie this impairment remain elusive. We combined high-resolution eye tracking with computational modeling in a group of 10 high-functioning individuals with autism to address this issue. The group fixated the location of the mouth in facial expressions more than did matched controls, even when the mouth was not shown, even in faces that were inverted and most noticeably at latencies of 200-400 ms. Comparisons with a computational model of visual saliency argue that the abnormal bias for fixating the mouth in autism is not driven by an exaggerated sensitivity to the bottom-up saliency of the features, but rather by an abnormal top-down strategy for allocating visual attention.

Electrocortical reflections of face and gaze processing in children with pervasive developmental disorder

BACKGROUND

Children with pervasive developmental disorder (PDD) show behavioral abnormalities in gaze and face processing, but recent studies have indicated that normal activation of face-specific brain areas in response to faces is possible in this group. It is not clear whether the brain activity related to gaze processing is also normal in children with PDD.

METHODS

Event-related brain potentials (ERPs) were measured during two spatial attention tasks in which a centrally presented stimulus served as cue for the location of a forthcoming target. In one task faces were used as cues, and in the other arrows. Seventeen children with PDD and 18 age- and IQ-matched control children were tested.

RESULTS

Face stimuli elicited the same specific ERP activity in both groups. Also, both children with PDD and controls showed shorter reaction times as well as larger amplitudes and shorter latency times of several ERP peaks to congruently cued targets than to incongruently cued targets in both tasks. However, children with PDD showed abnormally small occipital ERPs in response to both face and arrow stimuli.

CONCLUSIONS

The results provide evidence for the capability of normal processing of face and gaze change in children with PDD. The smaller occipital activity might be related to more general abnormalities in perception.