Neural signatures of autism

From early markers to neuro-developmental mechanisms of autism

•

Studies of infants at-risk could reveal the developmental origin of autism.

•

Behavioral and brain markers differentiate infants that develop autism symptoms from controls, during the first year of life.

•

Little evidence for decreased social orienting or social motivation.

•

Some evidence for multiple developmental pathways to autism.

A fast growing field, the study of infants at risk because of having an older sibling with autism (i.e. infant sibs) aims to identify the earliest signs of this disorder, which would allow for earlier diagnosis and intervention. More importantly, we argue, these studies offer the opportunity to validate existing neuro-developmental models of autism against experimental evidence. Although autism is mainly seen as a disorder of social interaction and communication, emerging early markers do not exclusively reflect impairments of the “social brain”. Evidence for atypical development of sensory and attentional systems highlight the need to move away from localized deficits to models suggesting brain-wide involvement in autism pathology. We discuss the implications infant sibs findings have for future work into the biology of autism and the development of interventions.

Individual differences in impulsivity predict head motion during magnetic resonance imaging

Magnetic resonance imaging (MRI) provides valuable data for understanding the human mind and brain disorders, but in-scanner head motion introduces systematic and spurious biases. For example, differences in MRI measures (e.g., network strength, white matter integrity) between patient and control groups may be due to the differences in their head motion. To determine whether head motion is an important variable in itself, or just simply a confounding variable, we explored individual differences in psychological traits that may predispose some people to move more than others during an MRI scan. In the first two studies, we demonstrated in both children (N  =  245) and adults (N  =  581) that head motion, estimated from resting-state functional MRI and diffusion tensor imaging, was reliably correlated with impulsivity scores. Further, the difference in head motion between children with attention deficit hyperactivity disorder (ADHD) and typically developing children was largely due to differences in impulsivity. Finally, in the third study, we confirmed the observation that the regression approach, which aims to deal with motion issues by regressing out motion in the group analysis, would underestimate the effect of interest. Taken together, the present findings provide empirical evidence that links in-scanner head motion to psychological traits.

Neocerebellar contributions to social perception in adolescents with autism spectrum disorder

•

Previous work shows cerebellar Crus I supports imitation via interaction with pSTS.

•

Teens with (ASD) and without (TD) autism completed an imitation task in the scanner.

•

Teens with ASD recruited Crus I less strongly during imitation than TD teens.

•

PPI strength between pSTS and Crus I predicted mentalizing in teens with ASD.

Posterior superior temporal sulcus (pSTS) is specialized for interpreting perceived human actions, and disruptions to its function occur in autism spectrum disorder (ASD). Here we consider the role of Crus I of neocerebellum in supporting pSTS function. Research has associated Crus I activity with imitation and biological motion perception, and neocerebellum is theorized to coordinate activity among cerebral sites more generally. Moreover, cerebellar abnormalities have been associated with ASD. We hypothesized that disordered Crus I–pSTS interactions could predict social deficits in ASD. 15 high functioning adolescents with ASD and 15 same-age comparison youth participated in an fMRI imitation paradigm; ratings of mentalizing ability were collected via parent report. We predicted that stronger Crus I–pSTS interactions would be associated with better mentalizing ability. Consistent with these hypotheses, stronger psychophysiological interactions between Crus I and right pSTS were associated with greater mentalizing ability among adolescents with ASD. Whole-brain analyses also indicated that typically developing youth recruited right inferior frontal gyrus, left pSTS, medial occipital regions, and precuneus more strongly during imitation than did youth with ASD. Overall, these results indicate that variability in neocerebellar interactions with key cortical social brain sites may help explain individual differences in social perceptual outcomes in ASD.

Sex Differences in the Neuromagnetic Cortical Response to Biological Motion

Body motion is a rich source of information for social interaction, and visual biological motion processing may be considered as a hallmark of social cognition. It is unclear, however, whether the social brain is sex specific. Here we assess sex impact on the magnetoencephalographic (MEG) cortical response to point-light human locomotion. Sex differences in the cortical MEG response to biological motion occur mostly over the right brain hemisphere. At early latencies, females exhibit a greater activation than males over the right parietal, left temporal, and right temporal cortex, a core of the social brain. At later latencies, the boosts of activation are greater in males over the right frontal and occipital cortices. The findings deliver the first evidence for gender-dependent modes in the time course and topography of the neural circuitry underpinning visual processing of biological motion. The outcome represents a framework for studying sex differences in the social brain in psychiatric and neurodevelopmental disorders.

Visual event-related potentials to biological motion stimuli in autism spectrum disorders

Atypical visual processing of biological motion contributes to social impairments in autism spectrum disorders (ASD). However, the exact temporal sequence of deficits of cortical biological motion processing in ASD has not been studied to date. We used 64-channel electroencephalography to study event-related potentials associated with human motion perception in 17 children and adolescents with ASD and 21 typical controls. A spatio-temporal source analysis was performed to assess the brain structures involved in these processes. We expected altered activity already during early stimulus processing and reduced activity during subsequent biological motion specific processes in ASD. In response to both, random and biological motion, the P100 amplitude was decreased suggesting unspecific deficits in visual processing, and the occipito-temporal N200 showed atypical lateralization in ASD suggesting altered hemispheric specialization. A slow positive deflection after 400 ms, reflecting top-down processes, and human motion-specific dipole activation differed slightly between groups, with reduced and more diffuse activation in the ASD-group. The latter could be an indicator of a disrupted neuronal network for biological motion processing in ADS. Furthermore, early visual processing (P100) seems to be correlated to biological motion-specific activation. This emphasizes the relevance of early sensory processing for higher order processing deficits in ASD.

Developmental process emerges from extended brain-body-behavior networks

Studies of brain connectivity have focused on two modes of networks: structural networks describing neuroanatomy and the intrinsic and evoked dependencies of functional networks at rest and during tasks. Each mode constrains and shapes the other across multiple timescales and each also shows age-related changes. Here we argue that understanding how brains change across development requires understanding the interplay between behavior and brain networks: changing bodies and activities modify the statistics of inputs to the brain; these changing inputs mold brain networks; and these networks, in turn, promote further change in behavior and input.

Abnormal Neural Activation to Faces in the Parents of Children with Autism

Parents of children with an autism spectrum disorder (ASD) show subtle deficits in aspects of social behavior and face processing, which resemble those seen in ASD, referred to as the "Broad Autism Phenotype " (BAP). While abnormal activation in ASD has been reported in several brain structures linked to social cognition, little is known regarding patterns in the BAP. We compared autism parents with control parents with no family history of ASD using 2 well-validated face-processing tasks. Results indicated increased activation in the autism parents to faces in the amygdala (AMY) and the fusiform gyrus (FG), 2 core face-processing regions. Exploratory analyses revealed hyper-activation of lateral occipital cortex (LOC) bilaterally in autism parents with aloof personality ("BAP+"). Findings suggest that abnormalities of the AMY and FG are related to underlying genetic liability for ASD, whereas abnormalities in the LOC and right FG are more specific to behavioral features of the BAP. Results extend our knowledge of neural circuitry underlying abnormal face processing beyond those previously reported in ASD to individuals with shared genetic liability for autism and a subset of genetically related individuals with the BAP.

The autism brain imaging data exchange: towards a large-scale evaluation of the intrinsic brain architecture in autism

Autism spectrum disorders (ASDs) represent a formidable challenge for psychiatry and neuroscience because of their high prevalence, lifelong nature, complexity and substantial heterogeneity. Facing these obstacles requires large-scale multidisciplinary efforts. Although the field of genetics has pioneered data sharing for these reasons, neuroimaging had not kept pace. In response, we introduce the Autism Brain Imaging Data Exchange (ABIDE)-a grassroots consortium aggregating and openly sharing 1112 existing resting-state functional magnetic resonance imaging (R-fMRI) data sets with corresponding structural MRI and phenotypic information from 539 individuals with ASDs and 573 age-matched typical controls (TCs; 7-64 years) (http://fcon_1000.projects.nitrc.org/indi/abide/). Here, we present this resource and demonstrate its suitability for advancing knowledge of ASD neurobiology based on analyses of 360 male subjects with ASDs and 403 male age-matched TCs. We focused on whole-brain intrinsic functional connectivity and also survey a range of voxel-wise measures of intrinsic functional brain architecture. Whole-brain analyses reconciled seemingly disparate themes of both hypo- and hyperconnectivity in the ASD literature; both were detected, although hypoconnectivity dominated, particularly for corticocortical and interhemispheric functional connectivity. Exploratory analyses using an array of regional metrics of intrinsic brain function converged on common loci of dysfunction in ASDs (mid- and posterior insula and posterior cingulate cortex), and highlighted less commonly explored regions such as the thalamus. The survey of the ABIDE R-fMRI data sets provides unprecedented demonstrations of both replication and novel discovery. By pooling multiple international data sets, ABIDE is expected to accelerate the pace of discovery setting the stage for the next generation of ASD studies.

Annual research review: Towards a developmental neuroscience of atypical social cognition

As a starting point for our review we use a developmental timeline, starting from birth and divided into major developmental epochs defined by key milestones of social cognition in typical development. For each epoch, we highlight those developmental disorders that diverge from the normal developmental pattern, what is known about these key milestones in the major disorders affecting social cognition, and any available research on the neural basis of these differences. We relate behavioural observations to four major networks of the social brain, that is, Amygdala, Mentalizing, Emotion and Mirror networks. We focus on those developmental disorders that are characterized primarily by social atypicality, such as autism spectrum disorder, social anxiety and a variety of genetically defined syndromes. The processes and aspects of social cognition we highlight are sketched in a putative network diagram, and include: agent identification, emotion processing and empathy, mental state attribution, self-processing and social hierarchy mapping involving social ‘policing’ and in-group/out-group categorization. Developmental disorders reveal some dissociable deficits in different components of this map of social cognition. This broad review across disorders, ages and aspects of social cognition leads us to some key questions: How can we best distinguish primary from secondary social disorders? Is social cognition especially vulnerable to developmental disorder, or surprisingly robust? Are cascading notions of social development, in which early functions are essential stepping stones or building bricks for later abilities, necessarily correct?

Attribution of emotions to body postures: an independent component analysis study of functional connectivity in autism

The ability to interpret others' body language is a vital skill that helps us infer their thoughts and emotions. However, individuals with autism spectrum disorder (ASD) have been found to have difficulty in understanding the meaning of people's body language, perhaps leading to an overarching deficit in processing emotions. The current fMRI study investigates the functional connectivity underlying emotion and action judgment in the context of processing body language in high-functioning adolescents and young adults with autism, using an independent components analysis (ICA) of the fMRI time series. While there were no reliable group differences in brain activity, the ICA revealed significant involvement of occipital and parietal regions in processing body actions; and inferior frontal gyrus, superior medial prefrontal cortex, and occipital cortex in body expressions of emotions. In a between-group analysis, participants with autism, relative to typical controls, demonstrated significantly reduced temporal coherence in left ventral premotor cortex and right superior parietal lobule while processing emotions. Participants with ASD, on the other hand, showed increased temporal coherence in left fusiform gyrus while inferring emotions from body postures. Finally, a positive predictive relationship was found between empathizing ability and the brain areas underlying emotion processing in ASD participants. These results underscore the differential role of frontal and parietal brain regions in processing emotional body language in autism.

Recognition of facial emotion and affective prosody in children with ASD (+ADHD) and their unaffected siblings

Autism is a highly heritable and clinically heterogeneous neuropsychiatric disorder that frequently co-occurs with other psychopathologies, such as attention-deficit/hyperactivity disorder (ADHD). An approach to parse heterogeneity is by forming more homogeneous subgroups of autism spectrum disorder (ASD) patients based on their underlying, heritable cognitive vulnerabilities (endophenotypes). Emotion recognition is a likely endophenotypic candidate for ASD and possibly for ADHD. Therefore, this study aimed to examine whether emotion recognition is a viable endophenotypic candidate for ASD and to assess the impact of comorbid ADHD in this context. A total of 90 children with ASD (43 with and 47 without ADHD), 79 ASD unaffected siblings, and 139 controls aged 6-13 years, were included to test recognition of facial emotion and affective prosody. Our results revealed that the recognition of both facial emotion and affective prosody was impaired in children with ASD and aggravated by the presence of ADHD. The latter could only be partly explained by typical ADHD cognitive deficits, such as inhibitory and attentional problems. The performance of unaffected siblings could overall be considered at an intermediate level, performing somewhat worse than the controls and better than the ASD probands. Our findings suggest that emotion recognition might be a viable endophenotype in ASD and a fruitful target in future family studies of the genetic contribution to ASD and comorbid ADHD. Furthermore, our results suggest that children with comorbid ASD and ADHD are at highest risk for emotion recognition problems.

Atypical interference effect of action observation in autism spectrum conditions

BACKGROUND

Observing incongruent actions interferes with ongoing action execution. This 'interference effect' is larger for observed biological actions than for non-biological actions. The current study used virtual reality to investigate the biological specificity of interference effects of action observation in autism spectrum conditions (ASC).

METHOD

High-functioning adults with ASC and age- and IQ-matched healthy controls performed horizontal sinusoidal arm movements whilst observing arm movements conducted by a virtual reality agent with either human or robot form, which moved with either biological motion or at a constant velocity. In another condition, participants made the same arm movements while observing a real human. Observed arm movements were either congruent or incongruent with executed arm movements. An interference effect was calculated as the average variance in the incongruent action dimension during observation of incongruent compared with congruent movements.

RESULTS

Control participants exhibited an interference effect when observing real human and virtual human agent incongruent movements but not when observing virtual robot agent movements. Individuals with ASC differed from controls in that they showed no interference effects for real human, virtual human or virtual robot movements.

CONCLUSIONS

The current study demonstrates atypical interference effects in ASC.

Biomarkers in autism spectrum disorder: the old and the new

RATIONALE

Autism spectrum disorder (ASD) is a complex heterogeneous neurodevelopmental disorder with onset during early childhood and typically a life-long course. The majority of ASD cases stems from complex, 'multiple-hit', oligogenic/polygenic underpinnings involving several loci and possibly gene-environment interactions. These multiple layers of complexity spur interest into the identification of biomarkers able to define biologically homogeneous subgroups, predict autism risk prior to the onset of behavioural abnormalities, aid early diagnoses, predict the developmental trajectory of ASD children, predict response to treatment and identify children at risk for severe adverse reactions to psychoactive drugs.

OBJECTIVES

The present paper reviews (a) similarities and differences between the concepts of 'biomarker' and 'endophenotype', (b) established biomarkers and endophenotypes in autism research (biochemical, morphological, hormonal, immunological, neurophysiological and neuroanatomical, neuropsychological, behavioural), (c) -omics approaches towards the discovery of novel biomarker panels for ASD, (d) bioresource infrastructures and (e) data management for biomarker research in autism.

RESULTS

Known biomarkers, such as abnormal blood levels of serotonin, oxytocin, melatonin, immune cytokines and lymphocyte subtypes, multiple neuropsychological, electrophysiological and brain imaging parameters, will eventually merge with novel biomarkers identified using unbiased genomic, epigenomic, transcriptomic, proteomic and metabolomic methods, to generate multimarker panels. Bioresource infrastructures, data management and data analysis using artificial intelligence networks will be instrumental in supporting efforts to identify these biomarker panels.

CONCLUSIONS

Biomarker research has great heuristic potential in targeting autism diagnosis and treatment.

Visual processing of biological motion in children and adolescents with attention-deficit/hyperactivity disorder: an event related potential-study

Attention-deficit/hyperactivity disorder (ADHD) is often accompanied by problems in social behaviour, which are sometimes similar to some symptoms of autism-spectrum disorders (ASD). However, neuronal mechanisms of ASD-like deficits in ADHD have rarely been studied. The processing of biological motion-recently discussed as a marker of social cognition-was found to be disrupted in ASD in several studies. Thus in the present study we tested if biological motion processing is disrupted in ADHD. We used 64-channel EEG and spatio-temporal source analysis to assess event-related potentials associated with human motion processing in 21 children and adolescents with ADHD and 21 matched typically developing controls. On the behavioural level, all subjects were able to differentiate between human and scrambled motion. But in response to both scrambled and biological motion, the N200 amplitude was decreased in subjects with ADHD. After a spatio-temporal dipole analysis, a human motion specific activation was observable in occipital-temporal regions with a reduced and more diffuse activation in ADHD subjects. These results point towards neuronal determined alterations in the processing of biological motion in ADHD.

Development of brain mechanisms for processing affective touch

Affective tactile stimulation plays a key role in the maturation of neural circuits, but the development of brain mechanisms processing touch is poorly understood. We therefore used functional magnetic resonance imaging (fMRI) to study brain responses to soft brush stroking of both glabrous (palm) and hairy (forearm) skin in healthy children (5-13 years), adolescents (14-17 years), and adults (25-35 years). Adult-defined regions-of-interests in the primary somatosensory cortex (SI), secondary somatosensory cortex (SII), insular cortex and right posterior superior temporal sulcus (pSTS) were significantly and similarly activated in all age groups. Whole-brain analyses revealed that responses in the ipsilateral SII were positively correlated with age in both genders, and that responses in bilateral regions near the pSTS correlated significantly and strongly with age in females but not in males. These results suggest that brain mechanisms associated with both sensory-discriminative and affective-motivational aspects of touch are largely established in school-aged children, and that there is a general continuing maturation of SII and a female-specific increase in pSTS sensitivity with age. Our work establishes a groundwork for future comparative studies of tactile processing in developmental disorders characterized by disrupted social perception such as autism.

Building a social neuroscience of autism spectrum disorder

Autism spectrum disorder (ASD) is an early onset neurodevelopmental disorder marked by impairments in reciprocal social interaction, communication, and the presence of repetitive or restricted interests and behaviors. Despite great phenotypic heterogeneity and etiologic diversity in ASD, social dysfunction is the unifying feature of ASD. This chapter focuses on understanding the neural systems involved in the processing of social information and its disruption in ASD by reviewing the conceptual background and highlighting some recent advances. In addition, work investigating an alternative interpretation of autistic dysfunction, problems with interconnectivity, and consequent difficulties with complex information processing are addressed.

Oxytocin enhances brain function in children with autism

Following intranasal administration of oxytocin (OT), we measured, via functional MRI, changes in brain activity during judgments of socially (Eyes) and nonsocially (Vehicles) meaningful pictures in 17 children with high-functioning autism spectrum disorder (ASD). OT increased activity in the striatum, the middle frontal gyrus, the medial prefrontal cortex, the right orbitofrontal cortex, and the left superior temporal sulcus. In the striatum, nucleus accumbens, left posterior superior temporal sulcus, and left premotor cortex, OT increased activity during social judgments and decreased activity during nonsocial judgments. Changes in salivary OT concentrations from baseline to 30 min postadministration were positively associated with increased activity in the right amygdala and orbitofrontal cortex during social vs. nonsocial judgments. OT may thus selectively have an impact on salience and hedonic evaluations of socially meaningful stimuli in children with ASD, and thereby facilitate social attunement. These findings further the development of a neurophysiological systems-level understanding of mechanisms by which OT may enhance social functioning in children with ASD.

Common polymorphism in the oxytocin receptor gene (OXTR) is associated with human social recognition skills

The neuropeptides oxytocin and vasopressin are evolutionarily conserved regulators of social perception and behavior. Evidence is building that they are critically involved in the development of social recognition skills within rodent species, primates, and humans. We investigated whether common polymorphisms in the genes encoding the oxytocin and vasopressin 1a receptors influence social memory for faces. Our sample comprised 198 families, from the United Kingdom and Finland, in whom a single child had been diagnosed with high-functioning autism. Previous research has shown that impaired social perception, characteristic of autism, extends to the first-degree relatives of autistic individuals, implying heritable risk. Assessments of face recognition memory, discrimination of facial emotions, and direction of gaze detection were standardized for age (7-60 y) and sex. A common SNP in the oxytocin receptor (rs237887) was strongly associated with recognition memory in combined probands, parents, and siblings after correction for multiple comparisons. Homozygotes for the ancestral A allele had impairments in the range -0.6 to -1.15 SD scores, irrespective of their diagnostic status. Our findings imply that a critical role for the oxytocin system in social recognition has been conserved across perceptual boundaries through evolution, from olfaction in rodents to visual memory in humans.

Preterm birth and adolescent social functioning-alterations in emotion-processing brain areas

OBJECTIVE

To investigate the relationship between preterm birth, adolescent, and adult psychosocial outcomes, and alterations in gray matter volume.

STUDY DESIGN

Individuals (n = 73) born at <33 weeks of gestation (very preterm) and 49 controls completed the Child Behavior Checklist (CBCL) at age 15 years to identify 'social immaturity' (SI) cases. Voxel-based morphometry was used to investigate gray matter volumes according to CBCL-SI 'caseness.' The Clinical Interview Schedule-Revised (CIS-R) was administered at age 19 years.

RESULTS

Very preterm adolescents were almost 4 times more likely to reach CBCL-SI 'caseness' compared with controls. Ex-preterm SI 'cases' had increased gray matter volume in the fusiform gyrus bilaterally (Talairach coordinates: x = 60, y = -27, z = -30; Z = 3.78; x = -61, y = -35, z = -27; Z = 3.56, after correction for multiple comparisons) compared with ex-preterm SI 'noncases.' Left fusiform volume displayed a stronger correlation with ipsilateral orbitofrontal cortex in SI 'cases' (x = -15, y = 22, z = -26; Z = 3.64). CIS-R total scores were slightly higher in ex-preterm individuals compared with controls. In the whole sample, SI 'cases' in midadolescence also had higher CIS-R scores in adulthood compared with 'noncases' (SI 'cases': mean = 5.7, 95% CI = 4.0-7.4; SI 'noncases': mean = 2.7, 95% CI = 1.1-4.3; F = 6.4, df = 74; P = .013).

CONCLUSIONS

Ex-preterm adolescents had increased socialization problems in adolescence, which were associated with volumetric alterations in an emotion-processing brain network. Atypical social development is linked to an increased vulnerability to psychiatric disorder.

Atypical basic movement kinematics in autism spectrum conditions

Individuals with autism spectrum conditions have difficulties in understanding and responding appropriately to others. Additionally, they demonstrate impaired perception of biological motion and problems with motor control. Here we investigated whether individuals with autism move with an atypical kinematic profile, which might help to explain perceptual and motor impairments, and in principle may contribute to some of their higher level social problems. We recorded trajectory, velocity, acceleration and jerk while adult participants with autism and a matched control group conducted horizontal sinusoidal arm movements. Additionally, participants with autism took part in a biological motion perception task in which they classified observed movements as ‘natural’ or ‘unnatural’. Results show that individuals with autism moved with atypical kinematics; they did not minimize jerk to the same extent as the matched typical control group, and moved with greater acceleration and velocity. The degree to which kinematics were atypical was correlated with a bias towards perceiving biological motion as ‘unnatural’ and with the severity of autism symptoms as measured by the Autism Diagnostic Observation Schedule. We suggest that fundamental differences in movement kinematics in autism might help to explain their problems with motor control. Additionally, developmental experience of their own atypical kinematic profiles may lead to disrupted perception of others’ actions.

Investigating mechanisms underlying neurodevelopmental phenotypes of autistic and intellectual disability disorders: a perspective

Brain function and behavior undergo significant plasticity and refinement, particularly during specific critical and sensitive periods. In autistic and intellectual disability (ID) neurodevelopmental disorders (NDDs) and their corresponding genetic mouse models, impairments in many neuronal and behavioral phenotypes are temporally regulated and in some cases, transient. However, the links between neurobiological mechanisms governing typically normal brain and behavioral development (referred to also as "neurotypical" development) and timing of NDD impairments are not fully investigated. This perspective highlights temporal patterns of synaptic and neuronal impairment, with a restricted focus on autism and ID types of NDDs. Given the varying known genetic and environmental causes for NDDs, this perspective proposes two strategies for investigation: (1) a focus on neurobiological mechanisms underlying known critical periods in the (typically) normal-developing brain; (2) investigation of spatio-temporal expression profiles of genes implicated in monogenic syndromes throughout affected brain regions. This approach may help explain why many NDDs with differing genetic causes can result in overlapping phenotypes at similar developmental stages and better predict vulnerable periods within these disorders, with implications for both therapeutic rescue and ultimately, prevention.

Brain mechanisms for prepulse inhibition in adults with Tourette syndrome: initial findings

Prepulse inhibition (PPI) of the startle reflex is disrupted in a number of developmental neuropsychiatric disorders, including Tourette syndrome (TS). This disruption is hypothesized to reflect abnormalities in sensorimotor gating. We applied whole-brain functional magnetic resonance imaging (fMRI) to elucidate the neural correlates of PPI in adult TS subjects using airpuff stimuli to the throat to elicit a tactile startle response. We used a cross-sectional, case-control study design and a blocked-design fMRI paradigm. There were 33 participants: 17 with TS and 16 healthy individuals. As a measure of PPI-related brain activity, we looked for differential cerebral activation to prepulse-plus-pulse stimuli versus activation to pulse-alone stimuli. In healthy subjects, PPI was associated with increased activity in multiple brain regions, of which activation in the left middle frontal gyrus in the healthy controls showed a significant linear correlation with the degree of PPI measured outside of the magnet. Group comparisons identified nine regions where brain activity during PPI differed significantly between TS and healthy subjects. Among the TS subjects, activation in the left caudate was significantly correlated with current tic severity as measured by the total score on the Yale Global Tic Severity Scale. Differential activation of the caudate nucleus associated with current tic severity is consistent with neuropathological data and suggests that portions of cortical-striatal circuits may modulate the severity of tic symptoms in adulthood.

Heterogeneity within Autism Spectrum Disorders: What have We Learned from Neuroimaging Studies?

Autism spectrum disorders (ASD) display significant heterogeneity. Although most neuroimaging studies in ASD have been designed to identify commonalities among affected individuals, rather than differences, some studies have explored variation within ASD. There have been two general types of approaches used for this in the neuroimaging literature to date: comparison of subgroups within ASD, and analyses using dimensional measures to link clinical variation to brain differences. This review focuses on structural and functional magnetic resonance imaging studies that have used these approaches to begin to explore heterogeneity between individuals with ASD. Although this type of data is yet sparse, recognition is growing of the limitations of behaviorally defined categorical diagnoses for understanding neurobiology. Study designs that are more informative regarding the sources of heterogeneity in ASD have the potential to improve our understanding of the neurobiological processes underlying ASD.

Neural processing of intentional biological motion in unaffected siblings of children with autism spectrum disorder: an fMRI study

Despite often showing behaviorally typical levels of social cognitive ability, unaffected siblings of children with autism spectrum disorder have been found to show similar functional and morphological deficits within brain regions associated with social processing. They have also been reported to show increased activation to biological motion in these same regions, such as the posterior superior temporal sulcus (pSTS), relative to both children with autism and control children. It has been suggested that this increased activation may represent a compensatory reorganization of these regions as a result of the highly heritable genetic influence of autism. However, the response patterns of unaffected siblings in the domain of action perception are unstudied, and the phenomenon of compensatory activation has not yet been replicated. The present study used functional magnetic resonance imaging to determine the neural responses to intentional biological actions in 22 siblings of children with autism and 22 matched controls. The presented actions were either congruent or incongruent with the actor's emotional cue. Prior studies reported that typically developing children and adults, but not children with autism, show increased activation to incongruent actions (relative to congruent), within the pSTS and dorsolateral prefrontal cortex. We report that unaffected siblings did not show a compensatory response, or a preference for incongruent over congruent trials, in any brain region. Moreover, interaction analyses revealed a sub-region of the pSTS in which control children showed an incongruency preference to a significantly greater degree than siblings, which suggests a localized deficit in siblings. A sample of children with autism also did not show differential activation in the pSTS, providing further evidence that it is an area of selective disruption in children with autism and siblings. While reduced activation to both conditions was unique to the autism sample, lack of differentiation to incongruent and congruent intentional actions was common to both children with ASD and unaffected siblings.

Underconnectivity of the superior temporal sulcus predicts emotion recognition deficits in autism

Neurodevelopmental disconnections have been assumed to cause behavioral alterations in autism spectrum disorders (ASDs). Here, we combined measurements of intrinsic functional connectivity (iFC) from resting-state functional magnetic resonance imaging (fMRI) with task-based fMRI to explore whether altered activity and/or iFC of the right posterior superior temporal sulcus (pSTS) mediates deficits in emotion recognition in ASD. Fifteen adults with ASD and 15 matched-controls underwent resting-state and task-based fMRI, during which participants discriminated emotional states from point light displays (PLDs). Intrinsic FC of the right pSTS was further examined using 584 (278 ASD/306 controls) resting-state data of the Autism Brain Imaging Data Exchange (ABIDE). Participants with ASD were less accurate than controls in recognizing emotional states from PLDs. Analyses revealed pronounced ASD-related reductions both in task-based activity and resting-state iFC of the right pSTS with fronto-parietal areas typically encompassing the action observation network (AON). Notably, pSTS-hypo-activity was related to pSTS-hypo-connectivity, and both measures were predictive of emotion recognition performance with each measure explaining a unique part of the variance. Analyses with the large independent ABIDE dataset replicated reductions in pSTS-iFC to fronto-parietal regions. These findings provide novel evidence that pSTS hypo-activity and hypo-connectivity with the fronto-parietal AON are linked to the social deficits characteristic of ASD.

Altered metabolites in the plasma of autism spectrum disorder: a capillary electrophoresis time-of-flight mass spectroscopy study

Clinical diagnosis and severity of autism spectrum disorders (ASD) are determined by trained clinicians based on clinical evaluations of observed behaviors. As such, this approach is inevitably dependent on the expertise and subjective assessment of those administering the clinical evaluations. There is a need to identify objective biological markers associated with diagnosis or clinical severity of the disorder. To identify novel candidate metabolites as potential biomarkers for ASD, the current study applied capillary electrophoresis time-of-flight mass spectroscopy (CE-TOFMS) for high-throughput profiling of metabolite levels in the plasma of 25 psychotropic-naïve adult males with high-functioning ASD and 28 age-matched typically-developed control subjects. Ten ASD participants and ten age-matched controls were assigned in the first exploration set, while 15 ASD participants and 18 controls were included in the second replication set. By CE-TOFMS analysis, a total of 143 metabolites were detected in the plasma of the first set. Of these, 17 metabolites showed significantly different relative areas between the ASD participants and the controls (p<0.05). Of the 17 metabolites, we consistently found that the ASD participants had significantly high plasma levels of arginine (p = 0.024) and taurine (p = 0.018), and significantly low levels of 5-oxoproline (p<0.001) and lactic acid (p = 0.031) compared with the controls in the second sample set. Further confirmatory analysis using quantification of absolute metabolite concentrations supported the robustness of high arginine (p = 0.001) and low lactic acid (p = 0.003) in the combined sample (n = 53). The present study identified deviated plasma metabolite levels associated with oxidative stress and mitochondrial dysfunction in individuals with ASD.

[Neurobiology of autism and attention deficit hyperactivity disorder by means of neuroimaging techniques: convergences and divergences]

In the clinical area, some symptoms of attention deficit hyperactivity disorder (ADHD) also present in patients with autism spectrum disorders (ASD). Research has shown that there are alterations in brain circuits that have an impact upon specific cognitive and behavioural failures in each of these disorders. Yet, little research has been conducted on the brain correlates underlying both the similarities and the differences in the symptoms. In this review, the structural and functional meta-analytical studies that have been carried out to date on ADHD and ASD have been analysed. On the one hand, there are convergences in the attentional dorsal, executive functions, visual, somatomotor circuits and the default activation circuit. These similarities can account for the comorbid manifestations between the disorders, such as failure in the integration of information, fine motor control and specific attention processes. On the other hand, specifically in ADHD, there is a deficit in the reward circuit and in the attentional ventral, which are systems involved in the measurement of the effects of reinforcement and monitoring of attention. In ASD, the circuits that are most strongly affected are those involved in social cognition and language processes. In conclusion, there are neuronal correlates in both disorders that explain both the convergent and divergent clinical and behavioural manifestations.

Equivalent neural responses in children and adolescents with and without autism during judgments of affect

•

Carefully matched control and ASD groups (IQ, age, gender).

•

fMRI study of self- and other-referential processing.

•

Equivalent neural activation in emotion processing regions in ASD relative to controls.

Previous research has noted disrupted patterns of neural activation during emotion, processing in individuals with autism spectrum disorders (ASD). However, prior research relied on, designs that may place greater cognitive load on individuals with ASD. In order to address this issue, we adapted the fMRI task of Ochsner et al. (2004a) for children by, presenting fewer stimuli, with fewer valence levels, and longer stimuli duration. A localizer sample of, typically developing children (n = 26) was used to construct regions of interest involved in emotional, processing. Activations in these regions during self- and other-referential emotion processing was, compared in age, IQ, gender matched groups (n = 17 ASD, n = 16 TD). Matched samples replicate, condition contrasts of the localizer, but no group differences were found in behavior measures or, neural activation. An exploratory functional connectivity analysis in a subset of the matched groups, also did not detect striking differences between the groups. These findings suggest that disruptions in activation in emotion processing neural networks in ASD is partially a function of task related cognitive load.

Sex differences in the development of brain mechanisms for processing biological motion

Disorders related to social functioning including autism and schizophrenia differ drastically in incidence and severity between males and females. Little is known about the neural systems underlying these sex-linked differences in risk and resiliency. Using functional magnetic resonance imaging and a task involving the visual perception of point-light displays of coherent and scrambled biological motion, we discovered sex differences in the development of neural systems for basic social perception. In adults, we identified enhanced activity during coherent biological motion perception in females relative to males in a network of brain regions previously implicated in social perception including amygdala, medial temporal gyrus, and temporal pole. These sex differences were less pronounced in our sample of school-age youth. We hypothesize that the robust neural circuitry supporting social perception in females, which diverges from males beginning in childhood, may underlie sex differences in disorders related to social processing.

Effects of child characteristics on the Autism Diagnostic Interview-Revised: implications for use of scores as a measure of ASD severity

The Autism Diagnostic Interview-Revised (ADI-R) is commonly used to inform diagnoses of autism spectrum disorders (ASD). Considering the time dedicated to using the ADI-R, it is of interest to expand the ways in which information obtained from this interview is used. The current study examines how algorithm totals reflecting past (ADI-Diagnostic) and current (ADI-Current) behaviors are influenced by child characteristics, such as demographics, behavioral problems and developmental level. Children with less language at the time of the interview had higher ADI-Diagnostic and ADI-Current. ADI-Diagnostic totals were also associated with age; parents of older children reported more severe past behaviors. Recommendations are provided regarding the use of the ADI-R as a measure of ASD severity, taking language and age into account.

The perils of global signal regression for group comparisons: a case study of Autism Spectrum Disorders

We have previously argued from a theoretical basis that the standard practice of regression of the Global Signal from the fMRI time series in functional connectivity studies is ill advised, particularly when comparing groups of participants. Here, we demonstrate in resting-state data from participants with an Autism Spectrum Disorder and matched controls that these concerns are also well founded in real data. Using the prior theoretical work to formulate predictions, we show: (1) rather than simply altering the mean or range of correlation values amongst pairs of brain regions, Global Signal Regression systematically alters the rank ordering of values in addition to introducing negative values, (2) it leads to a reversal in the direction of group correlation differences relative to other preprocessing approaches, with a higher incidence of both long-range and local correlation differences that favor the Autism Spectrum Disorder group, (3) the strongest group differences under other preprocessing approaches are the ones most altered by Global Signal Regression, and (4) locations showing group differences no longer agree with those showing correlations with behavioral symptoms within the Autism Spectrum Disorder group. The correlation matrices of both participant groups under Global Signal Regression were well predicted by our previous mathematical analyses, demonstrating that there is nothing mysterious about these results. Finally, when independent physiological nuisance measures are lacking, we provide a simple alternative approach for assessing and lessening the influence of global correlations on group comparisons that replicates our previous findings. While this alternative performs less well for symptom correlations than our favored preprocessing approach that includes removal of independent physiological measures, it is preferable to the use of Global Signal Regression, which prevents unequivocal conclusions about the direction or location of group differences.

A nexus model of the temporal-parietal junction

The temporal-parietal junction (TPJ) has been proposed to support either specifically social functions or non-specific processes of cognition such as memory and attention. To account for diverse prior findings, we propose a nexus model for TPJ function: overlap of basic processes produces novel secondary functions at their convergence. We present meta-analytic evidence that is consistent with the anatomical convergence of attention, memory, language, and social processing in the TPJ, leading to a higher-order role in the creation of a social context for behavior. The nexus model accounts for recent examples of TPJ contributions specifically to decision making in a social context and provides a potential reconciliation for competing claims about TPJ function.

Neural mechanisms of improvements in social motivation after pivotal response treatment: two case studies

Pivotal response treatment (PRT) is an empirically validated behavioral treatment that has widespread positive effects on communication, behavior, and social skills in young children with autism spectrum disorder (ASD). For the first time, functional magnetic resonance imaging was used to identify the neural correlates of successful response to PRT in two young children with ASD. Baseline measures of social communication, adaptive behavior, eye tracking and neural response to social stimuli were taken prior to treatment and after 4 months of PRT. Both children showed striking gains on behavioral measures and also showed increased activation to social stimuli in brain regions utilized by typically developing children. These results suggest that neural systems supporting social perception are malleable through implementation of PRT.

Limitations on the developing preterm brain: impact of periventricular white matter lesions on brain connectivity and cognition

Brain lesions to the white matter in peritrigonal regions, periventricular leukomalacia, in children who were born prematurely represent an important model for studying limitations on brain development. The lesional pattern is of early origin and bilateral, that constrains the compensatory potential of the brain. We suggest that (i) topography and severity of periventricular lesions may have a long-term predictive value for cognitive and social capabilities in preterm birth survivors; and (ii) periventricular lesions may impact cognitive and social functions by affecting brain connectivity, and thereby, the dissociable neural networks underpinning these functions. A further pathway to explore is the relationship between cerebral palsy and cognitive outcome. Restrictions caused by motor disability may affect active exploration of surrounding and social participation that may in turn differentially impinge on cognitive development and social cognition. As an outline for future research, we underscore sex differences, as the sex of a preterm newborn may shape the mechanisms by which the developing brain is affected.

Functional magnetic resonance imaging of autism spectrum disorders

This review presents an overview of functional magnetic resonance imaging findings in autism spectrum disorders (ASDS), although there is considerable heterogeneity with respect to results across studies, common themes have emerged, including: (i) hypoactivation in nodes of the "social brain" during social processing tasks, including regions within the prefrontal cortex, the posterior superior temporal sulcus, the amygdala, and the fusiform gyrus; (ii) aberrant frontostriatal activation during cognitive control tasks relevant to restricted and repetitive behaviors and interests, including regions within the dorsal prefrontal cortex and the basal ganglia; (iii) differential lateralization and activation of language processing and production regions during communication tasks; (iv) anomalous mesolimbic responses to social and nonsocial rewards; (v) task-based long-range functional hypoconnectivity and short-range hyper-connectivity; and (vi) decreased anterior-posterior functional connectivity during resting states. These findings provide mechanistic accounts of ASD pathophysiology and suggest directions for future research aimed at elucidating etiologic models and developing rationally derived and targeted treatments.

Enhanced neural responses to rule violation in children with autism: a comparison to social exclusion

The present study aimed to explore the neural correlates of two characteristic deficits in autism spectrum disorders (ASD); social impairment and restricted, repetitive behavior patterns. To this end, we used comparable experiences of social exclusion and rule violation to probe potentially atypical neural networks in ASD. In children and adolescents with and without ASD, we used the interactive ball-toss game (Cyberball) to elicit social exclusion and a comparable game (Cybershape) to elicit a non-exclusive rule violation. Using functional magnetic resonance imaging (fMRI), we identified group differences in brain responses to social exclusion and rule violation. Though both groups reported equal distress following exclusion, the right insula and ventral anterior cingulate cortex were hypoactive during exclusion in children with ASD. In rule violation, right insula and dorsal prefrontal cortex were hyperactive in ASD. Right insula showed a dissociation in activation; it was hypoactive to social exclusion and hyperactive to rule violation in the ASD group. Further probed, different regions of right insula were modulated in each game, highlighting differences in regional specificity for which subsequent analyses revealed differences in patterns of functional connectivity. These results demonstrate neurobiological differences in processing social exclusion and rule violation in children with ASD.

Impaired global, and compensatory local, biological motion processing in people with high levels of autistic traits

People with Autism Spectrum Disorder (ASD) are hypothesized to have poor high-level processing but superior low-level processing, causing impaired social recognition, and a focus on non-social stimulus contingencies. Biological motion perception provides an ideal domain to investigate exactly how ASD modulates the interaction between low and high-level processing, because it involves multiple processing stages, and carries many important social cues. We investigated individual differences among typically developing observers in biological motion processing, and whether such individual differences associate with the number of autistic traits. In Experiment 1, we found that individuals with fewer autistic traits were automatically and involuntarily attracted to global biological motion information, whereas individuals with more autistic traits did not show this pre-attentional distraction. We employed an action adaptation paradigm in the second study to show that individuals with more autistic traits were able to compensate for deficits in global processing with an increased involvement in local processing. Our findings can be interpreted within a predictive coding framework, which characterizes the functional relationship between local and global processing stages, and explains how these stages contribute to the perceptual difficulties associated with ASD.

Structural and functional brain correlates of behavioral outcomes during adolescence

Several studies have described an association between very preterm birth and behavioral and psychiatric outcomes in childhood and adolescence. The exact mechanisms underlying this association are unknown, but impaired neurodevelopment has been proposed as a possible etiological factor. Existing research suggests a selective vulnerability of brain regions associated with a variety of behavioral and psychiatric outcomes following very preterm birth. This article reviews studies that have directly explored the structural and functional brain correlates of behavioral outcomes in ex-preterm individuals, with an emphasis on attentional problems, overall mental health functioning including internalizing and externalizing scores, and psychosocial adjustment. The focus here is on neuroimaging research conducted during adolescence, a period of life associated with the emergence and early expression of several psychiatric disorders. The neurodevelopmental hypothesis is used as a theoretical framework, according to which early brain lesions interact with the developing brain to increase later vulnerability to psychopathology.

Brain mechanisms for processing affective touch

Despite the crucial role of touch in social development, there is very little functional magnetic resonance imaging (fMRI) research on brain mechanisms underlying social touch processing. The "skin as a social organ" hypothesis is supported by the discovery of C-tactile (CT) nerves that are present in hairy skin and project to the insular cortex. CT-fibers respond specifically well to slow, gentle touch such as that which occurs during close social interactions. Given the social significance of such touch researchers have proposed that the CT-system represents an evolutionarily conserved mechanism important for normative social development. However, it is currently unknown whether brain regions other than the insula are involved in processing CT-targeted touch. In the current fMRI study, we sought to characterize the brain regions involved in the perception of CT-supported affective touch. Twenty-two healthy adults received manual brush strokes to either the arm or palm. A direct contrast of the blood-oxygenation-level-dependent (BOLD) response to gentle brushing of the arm and palm revealed the involvement of a network of brain regions, in addition to the posterior insula, during CT-targeted affective touch to the arm. This network included areas known to be involved in social perception and social cognition, including the right posterior superior temporal sulcus and the medial prefrontal cortex (mPFC)/dorso anterior cingulate cortex (dACC). Connectivity analyses with an mPFC/dACC seed revealed coactivation with the left insula and amygdala during arm touch. These findings characterize a network of brain regions beyond the insula involved in coding CT-targeted affective touch.

Reduced neural sensitivity to social stimuli in infants at risk for autism

In the hope of discovering early markers of autism, attention has recently turned to the study of infants at risk owing to being the younger siblings of children with autism. Because the condition is highly heritable, later-born siblings of diagnosed children are at substantially higher risk for developing autism or the broader autism phenotype than the general population. Currently, there are no strong predictors of autism in early infancy and diagnosis is not reliable until around 3 years of age. Because indicators of brain functioning may be sensitive predictors, and atypical social interactions are characteristic of the syndrome, we examined whether temporal lobe specialization for processing visual and auditory social stimuli during infancy differs in infants at risk. In a functional near-infrared spectroscopy study, infants aged 4–6 months at risk for autism showed less selective neural responses to social stimuli (auditory and visual) than low-risk controls. These group differences could not be attributed to overall levels of attention, developmental stage or chronological age. Our results provide the first demonstration of specific differences in localizable brain function within the first 6 months of life in a group of infants at risk for autism. Further, these differences closely resemble known patterns of neural atypicality in children and adults with autism. Future work will determine whether these differences in infant neural responses to social stimuli predict either later autism or the broader autism phenotype frequently seen in unaffected family members.

Developmental meta-analysis of the functional neural correlates of autism spectrum disorders

OBJECTIVE

There is a pressing need to elucidate the brain-behavior interactions underlying autism spectrum disorders (ASD) given the marked rise in ASD diagnosis over the past decade. Functional magnetic resonance imaging (fMRI) has begun to address this need, but few fMRI studies have evaluated age-related changes in ASD. Therefore, we conducted a developmental analysis of activation likelihood estimation (ALE) meta-analysis to compare child versus adult ASD fMRI studies. We hypothesized that children and adolescents with ASD (<18 years old) would rely less on prefrontal cortex structures than adults (≥18 years old).

METHOD

PubMed and PsycInfo literature searches were conducted to identify task-dependent fMRI studies of children or adults with ASD. Then recent GingerALE software improvements were leveraged to perform direct comparisons of child (n = 18) versus adult (n = 24) studies.

RESULTS

ALE meta-analyses of social tasks showed that children and adolescents with ASD versus adults had significantly greater hyperactivation in the left post-central gyrus, and greater hypoactivation in the right hippocampus and right superior temporal gyrus. ALE meta-analyses of nonsocial tasks showed that children with ASD versus adults had significantly greater hyperactivation in the right insula and left cingulate gyrus, and hypoactivation in the right middle frontal gyrus.

CONCLUSION

Our data suggest that the neural alterations associated with ASD are not static, occurring only in early childhood. Instead, children with ASD have altered neural activity compared to adults during both social and nonsocial tasks, especially in fronto-temporal structures. Longitudinal neuroimaging studies are required to examine these changes prospectively, as potential targets for brain-based treatments for ASD.

Functional connectivity-based signatures of schizophrenia revealed by multiclass pattern analysis of resting-state fMRI from schizophrenic patients and their healthy siblings

BACKGROUND

Recently, a growing number of neuroimaging studies have begun to investigate the brains of schizophrenic patients and their healthy siblings to identify heritable biomarkers of this complex disorder. The objective of this study was to use multiclass pattern analysis to investigate the inheritable characters of schizophrenia at the individual level, by comparing whole-brain resting-state functional connectivity of patients with schizophrenia to their healthy siblings.

METHODS

Twenty-four schizophrenic patients, twenty-five healthy siblings and twenty-two matched healthy controls underwent the resting-state functional Magnetic Resonance Imaging (rs-fMRI) scanning. A linear support vector machine along with principal component analysis was used to solve the multi-classification problem. By reconstructing the functional connectivities with high discriminative power, three types of functional connectivity-based signatures were identified: (i) state connectivity patterns, which characterize the nature of disruption in the brain network of patients with schizophrenia; (ii) trait connectivity patterns, reflecting shared connectivities of dysfunction in patients with schizophrenia and their healthy siblings, thereby providing a possible neuroendophenotype and revealing the genetic vulnerability to develop schizophrenia; and (iii) compensatory connectivity patterns, which underlie special brain connectivities by which healthy siblings might compensate for an increased genetic risk for developing schizophrenia.

RESULTS

Our multiclass pattern analysis achieved 62.0% accuracy via leave-one-out cross-validation (p < 0.001). The identified state patterns related to the default mode network, the executive control network and the cerebellum. For the trait patterns, functional connectivities between the cerebellum and the prefrontal lobe, the middle temporal gyrus, the thalamus and the middle temporal poles were identified. Connectivities among the right precuneus, the left middle temporal gyrus, the left angular and the left rectus, as well as connectivities between the cingulate cortex and the left rectus showed higher discriminative power in the compensatory patterns.

CONCLUSIONS

Based on our experimental results, we saw some indication of differences in functional connectivity patterns in the healthy siblings of schizophrenic patients compared to other healthy individuals who have no relations with the patients. Our preliminary investigation suggested that the use of resting-state functional connectivities as classification features to discriminate among schizophrenic patients, their healthy siblings and healthy controls is meaningful.

Developmental changes in point-light walker processing during childhood: a two-year follow-up ERP study

Event-related potentials were measured in twenty-four children aged 6-15 years, at one-year intervals for two years, to investigate developmental changes in each subject's neural response to a point-light walker (PLW) and a scrambled PLW (sPLW) stimulus. One positive peak (P1) and two negative peaks (N1 and N2) were observed in both occipitotemporal regions at approximately 130, 200, and 300-400ms. The amplitude and latency of the P1 component measured by the occipital electrode decreased during development over the first one-year period. Negative amplitudes of both N1 and N2, induced by the PLW stimulus, were significantly larger than those induced by the sPLW stimulus. Moreover, for the P1-N1 amplitude, the values for the eight-year-old children were significantly larger than those for the twelve-year-old children. N1 and N2 latency at certain electrodes decreased with age, but no consistent changes were observed. These results suggest that enhanced electrophysiological responses to PLW can be observed in all age groups, and that the early components were changed even over the course of a single year at the age of twelve.

Brain mechanisms of plasticity in response to treatments for core deficits in autism

Autism spectrum disorders (ASD) are neurodevelopmental disorders characterized by social communication impairments and repetitive behaviors. Although the prevalence of ASD is estimated at 1 in 88, understanding of the neural mechanisms underlying the disorder is still emerging. Regions including the amygdala, superior temporal sulcus, orbitofrontal cortex, fusiform gyrus, medial prefrontal cortex, and insula have been implicated in social processing. Neuroimaging studies have demonstrated both anatomical and functional differences in these areas of the brain in individuals with ASD when compared to controls; however, research on the neural basis for response to treatment in ASD is limited. Results of the three studies that have examined the neural mechanisms underlying treatment response are promising; following treatment, the brains of individuals with ASD seem to "normalize," responding more similarly to those of typically developing individuals. The research in this area is in its early stages, and thus a focused effort examining the neural basis of treatment response in ASD is crucial.