Atypical Neural Activity in Males But Not Females with Autism Spectrum Disorder

Perceptual discrimination of action formidableness and friendliness and the impact of autistic traits

The ability to determine whether the actions of other individuals are friendly or formidable are key decisions we need to make to successfully navigate our complex social environment. In this study we measured perceptual performance when discriminating actions that vary in their friendliness or formidableness, and whether performance was related to the autistic traits of individuals. To do this, we developed an action morphing method to generate novel actions that lied along the action quality dimensions of formidableness and friendliness. In Experiment 1 we show that actions that vary along the formidableness or friendliness continua were rated as varying monotonically along the respective quality. In Experiment 2 we measured the ability of individuals with different levels of autistic traits to discriminate action formidableness and friendliness using adaptive 2-AFC procedures. We found considerable variation in perceptual thresholds when discriminating action formidableness (~ 540% interindividual variation) or friendliness (~ 1100% interindividual variation). Importantly, we found no evidence that autistic traits influenced perceptual discrimination of these action qualities. These results confirm that sensory enhancements with autistic traits are limited to lower level stimuli, and suggest that the perceptual processing of these complex social signals are not affected by autistic traits.

Differently different?: A commentary on the emerging social cognitive neuroscience of female autism

Autism is a neurodevelopmental condition, behaviourally identified, which is generally characterised by social communication differences, and restrictive and repetitive patterns of behaviour and interests. It has long been claimed that it is more common in males. This observed preponderance of males in autistic populations has served as a focussing framework in all spheres of autism-related issues, from recognition and diagnosis through to theoretical models and research agendas. One related issue is the near total absence of females in key research areas. For example, this paper reports a review of over 120 brain-imaging studies of social brain processes in autism that reveals that nearly 70% only included male participants or minimal numbers (just one or two) of females. Authors of such studies very rarely report that their cohorts are virtually female-free and discuss their findings as though applicable to all autistic individuals. The absence of females can be linked to exclusionary consequences of autism diagnostic procedures, which have mainly been developed on male-only cohorts. There is clear evidence that disproportionately large numbers of females do not meet diagnostic criteria and are then excluded from ongoing autism research. Another issue is a long-standing assumption that the female autism phenotype is broadly equivalent to that of the male autism phenotype. Thus, models derived from male-based studies could be applicable to females. However, it is now emerging that certain patterns of social behaviour may be very different in females. This includes a specific type of social behaviour called camouflaging or masking, linked to attempts to disguise autistic characteristics. With respect to research in the field of sex/gender cognitive neuroscience, there is emerging evidence of female differences in patterns of connectivity and/or activation in the social brain that are at odds with those reported in previous, male-only studies. Decades of research have excluded or overlooked females on the autistic spectrum, resulting in the construction of inaccurate and misleading cognitive neuroscience models, and missed opportunities to explore the brain bases of this highly complex condition. A note of warning needs to be sounded about inferences drawn from past research, but if future research addresses this problem of male bias, then a deeper understanding of autism as a whole, as well as in previously overlooked females, will start to emerge.

Brain glutathione and GABA+ levels in autistic children

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by social communication challenges and repetitive behaviors. Altered neurometabolite levels, including glutathione (GSH) and gamma-aminobutyric acid (GABA), have been proposed as potential contributors to the biology underlying ASD. This study investigated whether cerebral GSH or GABA levels differ between a cohort of children aged 8-12 years with ASD (n = 52) and typically developing children (TDC, n = 49). A comprehensive analysis of GSH and GABA levels in multiple brain regions, including the primary motor cortex (SM1), thalamus (Thal), medial prefrontal cortex (mPFC), and supplementary motor area (SMA), was conducted using single-voxel HERMES MR spectroscopy at 3T. The results revealed no significant differences in cerebral GSH or GABA levels between the ASD and TDC groups across all examined regions. These findings suggest that the concentrations of GSH (an important antioxidant and neuromodulator) and GABA (a major inhibitory neurotransmitter) do not exhibit marked alterations in children with ASD compared to TDC. A statistically significant positive correlation was observed between GABA levels in the SM1 and Thal regions with ADHD inattention scores. No significant correlation was found between metabolite levels and hyper/impulsive scores of ADHD, measures of core ASD symptoms (ADOS-2, SRS-P) or adaptive behavior (ABAS-2). While both GSH and GABA have been implicated in various neurological disorders, the current study provides valuable insights into the specific context of ASD and highlights the need for further research to explore other neurochemical alterations that may contribute to the pathophysiology of this complex disorder.

Examining whether adults with autism spectrum disorder encounter multiple problems in theory of mind: a study based on meta-analysis

Theory of mind (ToM) represents a complex ability, while persons with autism spectrum disorder (ASD) encounter difficulties in the processing of ToM. The present ToM-focused studies on adults with ASD report inconsistent results, possibly owing to the differences between tasks. For instance, different ToM-related tasks involve different cognitive abilities, but the development of these cognitive abilities is different among adults with ASD, thereby leading to different behaviors by the same individual with ASD in different tasks. Therefore, it is of vital significance to explore the potential reasons for inconsistencies in the existing studies based on the task classification perspective. Hence, this study primarily reviews the existing ToM tasks used in studies on adults with ASD; afterward, based on the forms and characteristics of the task, the current ToM tasks are classified into four categories-reading comprehension, perceptual scene comprehension, comprehensive scene comprehension , and self-other processing. Subsequently, a meta-analysis is undertaken to determine the difference in each ToM task category between the ASD group and the typically developing (TD) group. As a result, 110 research papers (including 3,205 adults with ASD and 3,675 TD adults) that fulfilled the stated criteria are examined in this study. The study findings suggest that adults with ASD demonstrate worse performance in terms of all four ToM task categories as compared to TD adults. Furthermore, compared with tasks of self-other processing and perceptual scene comprehension, adults with ASD perform worse in reading comprehension and comprehensive scene comprehension. This shows that the differences between tasks may exert a potential influence on the study results. Future studies should focus on different abilities involved in ToM processing and the choice of ToM tasks, in order to elucidate the critical problems of ToM in adults with ASD.

Brain Glutathione and GABA+ levels in autistic children

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by social communication challenges and repetitive behaviors. Altered neurometabolite levels, including glutathione (GSH) and gamma-aminobutyric acid (GABA), have been proposed as potential contributors to the biology underlying ASD. This study investigated whether cerebral GSH or GABA levels differ between a large cohort of children aged 8-12 years with ASD (n=52) and typically developing children (TDC, n=49). A comprehensive analysis of GSH and GABA levels in multiple brain regions, including the primary motor cortex (SM1), thalamus (Thal), medial prefrontal cortex (mPFC), and supplementary motor area (SMA), was conducted using single-voxel HERMES MR spectroscopy at 3T. The results revealed no significant differences in cerebral GSH or GABA levels between the ASD and TDC groups across all examined regions. These findings suggest that the concentrations of GSH (an important antioxidant and neuromodulator) and GABA (a major inhibitory neurotransmitter) do not exhibit marked alterations in children with ASD compared to TDC. A statistically significant positive correlation was observed between GABA levels in the SM1 and Thal regions with ADHD inattention scores. No significant correlation was found between metabolite levels and hyper/impulsive scores of ADHD, measures of core ASD symptoms (ADOS-2, SRS-P) or adaptive behavior (ABAS-2). While both GSH and GABA have been implicated in various neurological disorders, the current study provides valuable insights into the specific context of ASD and highlights the need for further research to explore other neurochemical alterations that may contribute to the pathophysiology of this complex disorder.

Exploring the role of autistic traits and eating disorder psychopathology on mentalising ability in the general population

BACKGROUND

This study evaluated the role of overlapping traits and characteristics related to autism spectrum disorder (autism) and anorexia nervosa (AN) in the general population, and the impact of these traits on mentalising ability.

METHODS

A sample of young adults (N = 306), aged 18-25 years, was recruited to complete an online study that consisted of 4 measures: the Autism-Spectrum Quotient, Eating Disorder Examination Questionnaire, the Mentalization Scale, and the Reading the Mind in the Eyes task.

RESULTS

Higher levels of autistic traits, particularly difficulty with attention switching, were associated with increased eating disorder psychopathology. Overall, autistic traits and eating disorder psychopathology were related among females, but not males. Difficulty with attention switching, however, was related to eating disorder psychopathology among both females and males. Autistic traits also appear to have a greater role in mentalising ability than does eating disorder psychopathology.

CONCLUSION

The role of attention switching in overlapping traits of autism and eating disorder psychopathology needs to be more comprehensively evaluated by future research, as does the role of biological sex. Expanded knowledge in this field will help to better understand and evaluate symptoms at presentation, leading to clearer diagnoses and potentially better treatment outcomes.

Autism and intention attribution test: a non-verbal evaluation with comic strips

BACKGROUND

Despite autism spectrum disorder (ASD) and mentalization being two words often associated in the literature, the assessment of this ability in individuals with ASD in the clinical setting is still limited. Indeed, there are no standardized Theory of Mind (ToM) tests that are adaptable to different cognitive profiles, such as individuals with language poverty, and intellectual or memory impairments. This study proposes a non-verbal test (Intentions Attribution-Comic Strip Test; IA-CST) to evaluate the ability to infer the intentions of others, a basic component of ToM, in the clinical setting.

METHOD

In Study 1, the test was administered to 261 healthy individuals and we performed structural validation using Exploratory Graph Analysis. In Study 2, the final version of the test was administered to 32 individuals with ASD to assess the known group validity of the measure by comparing their scores with a sample of IQ-matched controls. Moreover, we performed logistic regression and ROC curve to preliminarily assess the diagnostic performance of the IA-CST.

RESULTS

The IA-CST resulted in a 3-dimension measure with good structural stability. Group comparison indicated that the ASD group shows significantly lower performance in intention attribution but not in inferring causal consequences. The test demonstrated known group validity and that, preliminarily, it is suitable for implementation within the clinical practice.

CONCLUSIONS

The results support the IA-CST as a valid non-verbal task for evaluating intentions attribution in the clinical setting. Difficulties in ToM are early and relevant in ASD, so assessing these aspects is valuable for structuring individualized and evidence-based interventions.

Sex Differences in Functional Connectivity Between Resting State Brain Networks in Autism Spectrum Disorder

Functional brain connectivity (FBC) has previously been examined in autism spectrum disorder (ASD) between-resting-state networks (RSNs) using a highly sensitive and reproducible hypothesis-free approach. However, results have been inconsistent and sex differences have only recently been taken into consideration using this approach. We estimated main effects of diagnosis and sex and a diagnosis by sex interaction on between-RSNs FBC in 83 ASD (40 females/43 males) and 85 typically developing controls (TC; 43 females/42 males). We found increased connectivity between the default mode (DM) and (a) the executive control networks in ASD (vs. TC); (b) the cerebellum networks in males (vs. females); and (c) female-specific altered connectivity involving visual, language and basal ganglia (BG) networks in ASD-in suggestive compatibility with ASD cognitive and neuroscientific theories.

A psychometric investigation of the multiple-choice version of Animated Triangles Task to measure Theory of Mind in adolescence

The Animated Triangles Task (AT) is commonly used to measure Theory of Mind (ToM). AT can be scored by clinicians based on participants’ verbal responses (AT-verbal) or using a multiple-choice paradigm (AT-MCQ). This study aimed to evaluate the validity of the less time-consuming AT-MCQ. To do this, we examined agreement and correlations between the AT-MCQ and the original AT-verbal scores in 1546 adolescents from a population-based sample. As a supplementary analysis of known-groups validity, we examined if AT-MCQ was as sensitive as AT-verbal in detecting ToM-limitations in 54 adolescents with autism spectrum disorder (ASD), using register-data. The agreement between AT-verbal and AT-MCQ varied markedly across test items. Scores on the two scoring methods were weakly correlated. Both scoring methods weakly detected differences between adolescents with and without ASD in this population-based sample. Most participants had appropriate responses on both AT-MCQ and AT-verbal, which yielded overall acceptable agreement. However, the feasibility of using either scoring methods to measure ToM-limitations in adolescents from the general population is questionable.

Sex/gender differences in the human autistic brains: A systematic review of 20 years of neuroimaging research

Our current understanding of autism is largely based on clinical experiences and research involving male individuals given the male-predominance in prevalence and the under-inclusion of female individuals due to small samples, co-occurring conditions, or simply being missed for diagnosis. There is a significantly biased 'male lens' in this field with autistic females insufficiently understood. We therefore conducted a systematic review to examine how sex and gender modulate brain structure and function in autistic individuals. Findings from the past 20 years are yet to converge on specific brain regions/networks with consistent sex/gender-modulating effects. Despite at least three well-powered studies identifying specific patterns of significant sex/gender-modulation of autism-control differences, many other studies are likely underpowered, suggesting a critical need for future investigation into sex/gender-based heterogeneity with better-powered designs. Future research should also formally investigate the effects of gender, beyond biological sex, which is mostly absent in the current literature. Understanding the roles of sex and gender in the development of autism is an imperative step to extend beyond the 'male lens' in this field.

Repetitive transcranial magnetic stimulation (rTMS) in autism spectrum disorder: protocol for a multicentre randomised controlled clinical trial

INTRODUCTION

There are no well-established biomedical treatments for the core symptoms of autism spectrum disorder (ASD). A small number of studies suggest that repetitive transcranial magnetic stimulation (rTMS), a non-invasive brain stimulation technique, may improve clinical and cognitive outcomes in ASD. We describe here the protocol for a funded multicentre randomised controlled clinical trial to investigate whether a course of rTMS to the right temporoparietal junction (rTPJ), which has demonstrated abnormal brain activation in ASD, can improve social communication in adolescents and young adults with ASD.

METHODS AND ANALYSIS

This study will evaluate the safety and efficacy of a 4-week course of intermittent theta burst stimulation (iTBS, a variant of rTMS) in ASD. Participants meeting criteria for Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition ASD (n=150, aged 14-40 years) will receive 20 sessions of either active iTBS (600 pulses) or sham iTBS (in which a sham coil mimics the sensation of iTBS, but no active stimulation is delivered) to the rTPJ. Participants will undergo a range of clinical, cognitive, epi/genetic, and neurophysiological assessments before and at multiple time points up to 6 months after iTBS. Safety will be assessed via a structured questionnaire and adverse event reporting. The study will be conducted from November 2020 to October 2024.

ETHICS AND DISSEMINATION

The study was approved by the Human Research Ethics Committee of Monash Health (Melbourne, Australia) under Australia's National Mutual Acceptance scheme. The trial will be conducted according to Good Clinical Practice, and findings will be written up for scholarly publication.

TRIAL REGISTRATION NUMBER

Australian New Zealand Clinical Trials Registry (ACTRN12620000890932).

Do animated triangles reveal a marked difficulty among autistic people with reading minds?

LAY ABSTRACT

Autistic people are thought to have difficulty with mentalising (our drive to track and understand the minds of other people). Mentalising is often measured by the Frith-Happé Animations task, where individuals need to interpret the interactions of abstract shapes. This review article collated results from over 3000 people to assess how autistic people performed on the task. Analysis showed that autistic people tended to underperform compared to non-autistic people on the task, although the scale of the difference was moderate rather than large. Also, autistic people showed some difficulty with the non-mentalising as well as mentalising aspects of the task. These results raise questions about the scale and specificity of mentalising difficulties in autism. It also remains unclear how well mentalising difficulties account for the social challenges diagnostic of autism.

Brain-based sex differences in autism spectrum disorder across the lifespan: A systematic review of structural MRI, fMRI, and DTI findings

Females with autism spectrum disorder (ASD) have been long overlooked in neuroscience research, but emerging evidence suggests they show distinct phenotypic trajectories and age-related brain differences. Sex-related biological factors (e.g., hormones, genes) may play a role in ASD etiology and have been shown to influence neurodevelopmental trajectories. Thus, a lifespan approach is warranted to understand brain-based sex differences in ASD. This systematic review on MRI-based sex differences in ASD was conducted to elucidate variations across the lifespan and inform biomarker discovery of ASD in females We identified articles through two database searches. Fifty studies met criteria and underwent integrative review. We found that regions expressing replicable sex-by-diagnosis differences across studies overlapped with regions showing sex differences in neurotypical cohorts. Furthermore, studies investigating age-related brain differences across a broad age-span suggest distinct neurodevelopmental patterns in females with ASD. Qualitative comparison across youth and adult studies also supported this hypothesis. However, many studies collapsed across age, which may mask differences. Furthermore, accumulating evidence supports the female protective effect in ASD, although only one study examined brain circuits implicated in "protection." When synthesized with the broader literature, brain-based sex differences in ASD may come from various sources, including genetic and endocrine processes involved in brain "masculinization" and "feminization" across early development, puberty, and other lifespan windows of hormonal transition. Furthermore, sex-related biology may interact with peripheral processes, in particular the stress axis and brain arousal system, to produce distinct neurodevelopmental patterns in males and females with ASD. Future research on neuroimaging-based sex differences in ASD would benefit from a lifespan approach in well-controlled and multivariate studies. Possible relationships between behavior, sex hormones, and brain development in ASD remain largely unexamined.

Thalamic and prefrontal GABA concentrations but not GABAA receptor densities are altered in high-functioning adults with autism spectrum disorder

The gamma aminobutyric acid (GABA) neurotransmission system has been implicated in autism spectrum disorder (ASD). Molecular neuroimaging studies incorporating simultaneous acquisitions of GABA concentrations and GABAA receptor densities can identify objective molecular markers in ASD. We measured both total GABAA receptor densities by using [18F]flumazenil positron emission tomography ([18F]FMZ-PET) and GABA concentrations by using proton magnetic resonance spectroscopy (1H-MRS) in 28 adults with ASD and 29 age-matched typically developing (TD) individuals. Focusing on the bilateral thalami and the left dorsolateral prefrontal cortex (DLPFC) as our regions of interest, we found no differences in GABAA receptor densities between ASD and TD groups. However, 1H-MRS measurements revealed significantly higher GABA/Water (GABA normalized by water signal) in the left DLPFC of individuals with ASD than that of TD controls. Furthermore, a significant gender effect was observed in the thalami, with higher GABA/Water in males than in females. Hypothesizing that thalamic GABA correlates with ASD symptom severity in gender-specific ways, we stratified by diagnosis and investigated the interaction between gender and thalamic GABA/Water in predicting Autism-Spectrum Quotient (AQ) and Ritvo Autism Asperger's Diagnostic Scale-Revised (RAADS-R) total scores. We found that gender is a significant effect modifier of thalamic GABA/Water's relationship with AQ and RAADS-R scores for individuals with ASD, but not for TD controls. When we separated the ASD participants by gender, a negative correlation between thalamic GABA/Water and AQ was observed in male ASD participants. Remarkably, in female ASD participants, a positive correlation between thalamic GABA/Water and AQ was found.

Quantitative and Qualitative Sex Modulations in the Brain Anatomy of Autism

BACKGROUND

Sex-based neurobiological heterogeneity in autism is poorly understood. Research is disproportionately biased to males, leading to an unwarranted presumption that autism neurobiology is the same across sexes. Previous neuroimaging studies using amalgamated multicenter datasets to increase autistic female samples are characterized by large statistical noise.

METHODS

We used a better-powered dataset of 1183 scans of 839 individuals-299 (467 scans) autistic males, 74 (102 scans) autistic females, 240 (334 scans) control males, and 226 (280 scans) control females-to test two whole-brain models of overall/global sex modulations on autism neuroanatomy, by summary measures computed across the brain: the local magnitude model, in which the same brain regions/circuitries are involved across sexes but effect sizes are larger in females, indicating quantitative sex modulation; and spatial dissimilarity model, in which the neuroanatomy differs spatially between sexes, indicating qualitative sex modulation. The male and female autism groups were matched on age, IQ, and autism symptoms. Autism brain features were defined by comparisons with same-sex control individuals.

RESULTS

Across five metrics (cortical thickness, surface area, volume, mean absolute curvature, and subcortical volume), we found no evidence supporting the local magnitude model. We found indicators supporting the spatial dissimilarity model on cortical mean absolute curvature and subcortical volume, but not on other metrics.

CONCLUSIONS

The overall/global autism neuroanatomy in females and males does not simply differ quantitatively in the same brain regions/circuitries. They may differ qualitatively in spatial involvement in cortical curvature and subcortical volume. The neuroanatomy of autism may be partly sex specific. Sex stratification to inform autism preclinical/clinical research is needed to identify sex-informed neurodevelopmental targets.

Attributing social meaning to animated shapes: A new experimental study of apparent behavior

In 1944, Heider and Simmel reported that observers could perceive simple animated geometric shapes as characters with emotions, intentions, and other social attributes. This work has been cited over 3000 times and has had wide and ongoing influence on the study of social cognition and social intelligence. However, many researchers in this area have continued to use the original Heider and Simmel black-and-white video. We asked whether the original findings could be reproduced 75 years later by creating 32 new colored animated shape videos designed to depict various social plots and testing whether they can evoke similar spontaneous social attributions. Participants (N = 66) viewed our videos and were asked to write narratives which we coded for indicia of different types of social attributions. Consistent with Heider and Simmel, we found that participants spontaneously attributed social meaning to the videos. We observed that responses to our videos were also similar to responses to the original video reported by Klin (2000), despite being only 13-23 s and portraying a broader range of social plots. Participants varied in how many social attributions they made in response, and the videos varied in how much they elicited such responses. Our set of animated shape videos is freely available online for all researchers to use and forms the basis of a multiple-choice assessment of social intelligence (Brown et al., 2019).

Towards robust and replicable sex differences in the intrinsic brain function of autism

BACKGROUND

Marked sex differences in autism prevalence accentuate the need to understand the role of biological sex-related factors in autism. Efforts to unravel sex differences in the brain organization of autism have, however, been challenged by the limited availability of female data.

METHODS

We addressed this gap by using a large sample of males and females with autism and neurotypical (NT) control individuals (ABIDE; Autism: 362 males, 82 females; NT: 409 males, 166 females; 7-18 years). Discovery analyses examined main effects of diagnosis, sex and their interaction across five resting-state fMRI (R-fMRI) metrics (voxel-level Z > 3.1, cluster-level P < 0.01, gaussian random field corrected). Secondary analyses assessed the robustness of the results to different pre-processing approaches and their replicability in two independent samples: the EU-AIMS Longitudinal European Autism Project (LEAP) and the Gender Explorations of Neurogenetics and Development to Advance Autism Research.

RESULTS

Discovery analyses in ABIDE revealed significant main effects of diagnosis and sex across the intrinsic functional connectivity of the posterior cingulate cortex, regional homogeneity and voxel-mirrored homotopic connectivity (VMHC) in several cortical regions, largely converging in the default network midline. Sex-by-diagnosis interactions were confined to the dorsolateral occipital cortex, with reduced VMHC in females with autism. All findings were robust to different pre-processing steps. Replicability in independent samples varied by R-fMRI measures and effects with the targeted sex-by-diagnosis interaction being replicated in the larger of the two replication samples-EU-AIMS LEAP.

LIMITATIONS

Given the lack of a priori harmonization among the discovery and replication datasets available to date, sample-related variation remained and may have affected replicability.

CONCLUSIONS

Atypical cross-hemispheric interactions are neurobiologically relevant to autism. They likely result from the combination of sex-dependent and sex-independent factors with a differential effect across functional cortical networks. Systematic assessments of the factors contributing to replicability are needed and necessitate coordinated large-scale data collection across studies.

Challenges Surrounding the Diagnosis of Autism in Children

This comprehensive thematic review aims to highlight and familiarize readers with the challenges and pitfalls encountered in differential diagnosis of autism spectrum disorders (ASD) in children to facilitate the process of accurate identification by stakeholders. Accordingly, articles that best answer our questions and highlight our concerns were chosen from well-established publishers with prime peer reviewed journals. Included are studies showing alternate views of the issues so as to point readers to other possibilities. ASD, a complex dynamic biological-neurodevelopmental disorder, is underscored by its heterogeneous symptomology, severity, and phenotypes - all characterized by social communication deficits and presence of restricted interests and repetitive behaviours (RRBs), the core symptoms in ASD. Language and intellectual capacities do not form ASD core symptoms although vary considerably. Accurate identification is challenging as ASD is often enmeshed with other neurodevelopmental disorders, and medical comorbidities, a situation now recognized as the rule rather than the exception in child psychiatry and developmental medicine. ASD is a disorder with varying performance and severity of symptoms over time, including unexpected loss of early skills, and lost diagnosis in some children following treatment. The review reiterates the urgency in accurate diagnosis in face of the rapid rise in ASD prevalence globally, and risk-increase in delayed or denied treatment with undesirable life-long consequences for most of the affected children. In addition, a call for change is advised to circumvent the ethical dilemma posed by the present "deficit model" in ASD diagnosis. Here, ASD prevalence is presented first, followed by emphasis on importance of accurate early diagnosis, and challenges in its accomplishment due to flaws in diagnostic instruments and other contributing factors. Next follow the required criteria for accurate identification, and its difficulties attributed to comorbid conditions, gender differences, and socio-economic and cultural influences. The conclusion includes future directions and a take away message.

Neural Correlates of Theory of Mind Are Preserved in Young Women With Anorexia Nervosa

People with anorexia nervosa (AN) commonly exhibit social difficulties, which may be related to problems with understanding the perspectives of others, commonly known as Theory of Mind (ToM) processing. However, there is a dearth of literature investigating the neural basis of these differences in ToM and at what age they emerge. This study aimed to test for differences in the neural correlates of ToM processes in young women with AN, and young women weight-restored (WR) from AN, as compared to healthy control participants (HC). Based on previous findings in AN, we hypothesized that young women with current or prior AN, as compared to HCs, would exhibit a reduced neural response in the medial prefrontal cortex (mPFC), the inferior frontal gyrus, and the temporo-parietal junction (TPJ) whilst completing a ToM task. We recruited 73 young women with AN, 45 WR young women, and 70 young women without a history of AN to take part in the current study. Whilst undergoing a functional magnetic resonance imaging (fMRI) scan, participants completed the Frith-Happé task, which is a commonly used measure of ToM with demonstrated reliability and validity in adult populations. In this task, participants viewed the movements of triangles, which depicted either action movements, simple interactions, or complex social interactions. Viewing trials with more complex social interactions in the Frith-Happé task was associated with increased brain activation in regions including the right TPJ, the bilateral mPFC, the cerebellum, and the dorsolateral prefrontal cortex. There were no group differences in neural activation in response to the ToM contrast. Overall, these results suggest that the neural basis of spontaneous mentalizing is preserved in most young women with AN.

Fixel Based Analysis Reveals Atypical White Matter Micro- and Macrostructure in Adults With Autism Spectrum Disorder: An Investigation of the Role of Biological Sex

Atypical white matter (WM) microstructure is commonly implicated in the neuropathophysiology of autism spectrum disorder (ASD). Fixel based analysis (FBA), at the cutting-edge of diffusion-weighted imaging, can account for crossing WM fibers and can provide indices of both WM micro- and macrostructure. We applied FBA to investigate WM structure between 25 (12 males, 13 females) adults with ASD and 24 (12 males, 12 females) matched controls. As the role of biological sex on the neuropathophysiology of ASD is of increasing interest, this was also explored. There were no significant differences in WM micro- or macrostructure between adults with ASD and matched healthy controls. When data were stratified by sex, females with ASD had reduced fiber density and cross-section (FDC), a combined metric comprised of micro- and macrostructural measures, in the corpus callosum, a finding not detected between the male sub-groups. We conclude that micro- and macrostructural WM aberrations are present in ASD, and may be influenced by biological sex.

Neural Mechanisms of Vicarious Reward Processing in Adults with Autism Spectrum Disorder

Previous studies examining the neural substrates of reward processing in ASD have explored responses to rewards for oneself but not rewards earned for others (i.e., vicarious reward). This omission is notable given that vicarious reward processing is a critical component of creating and maintaining social relationships. The current study examined the neural mechanisms of vicarious reward processing in 15 adults with ASD and 15 age- and gender-matched typically developing controls. Individuals with ASD demonstrated attenuated activation of reward-related regions during vicarious reward processing. Altered connectivity was also observed in individuals with ASD during reward receipt. These findings of altered neural sensitivity to vicarious reward processing may represent a mechanism that hinders the development of social abilities in ASD.

Autism spectrum disorder

Autism spectrum disorder is a construct used to describe individuals with a specific combination of impairments in social communication and repetitive behaviours, highly restricted interests and/or sensory behaviours beginning early in life. The worldwide prevalence of autism is just under 1%, but estimates are higher in high-income countries. Although gross brain pathology is not characteristic of autism, subtle anatomical and functional differences have been observed in post-mortem, neuroimaging and electrophysiological studies. Initially, it was hoped that accurate measurement of behavioural phenotypes would lead to specific genetic subtypes, but genetic findings have mainly applied to heterogeneous groups that are not specific to autism. Psychosocial interventions in children can improve specific behaviours, such as joint attention, language and social engagement, that may affect further development and could reduce symptom severity. However, further research is necessary to identify the long-term needs of people with autism, and treatments and the mechanisms behind them that could result in improved independence and quality of life over time. Families are often the major source of support for people with autism throughout much of life and need to be considered, along with the perspectives of autistic individuals, in both research and practice.

Sex/gender differences in neurology and psychiatry: Autism

Autism is a heterogenous set of early-onset neurodevelopmental conditions that are more prevalent in males than in females. Due to the high phenotypic, neurobiological, developmental, and etiological heterogeneity in the autism spectrum, recent research programs are increasingly exploring whether sex- and gender-related factors could be helpful markers to clarify the heterogeneity in autism and work toward a personalized approach to intervention and support. In this chapter, we summarize recent clinical and neuroscientific research addressing sex/gender influences in autism and explore how sex/gender-based investigations shed light on similar or different underlying neurodevelopmental mechanisms of autism by sex/gender. We review evidence that may help to explain some of the underlying sex-related biological mechanisms associated with autism, including genetics and the effects of sex steroid hormones in the prenatal environment. We conclude that current research points toward coexisting quantitative and, perhaps more evidently, qualitative sex/gender-modulation effects in autism across multiple neurobiological aspects. However, converging findings of specific neurobiological presentations and sex/gender-informed mechanisms cutting across the many subgroups within the autism spectrum are still lacking. Future research should use big data approaches and new stratification methods to decompose sex/gender-related heterogeneity in autism and work toward personalized, sex/gender-informed intervention and support for autistic people.

Neural self-representation in autistic women and association with 'compensatory camouflaging'

Prior work has revealed sex/gender-dependent autistic characteristics across behavioural and neural/biological domains. It remains unclear whether and how neural sex/gender differences are related to behavioural sex/gender differences in autism. Here, we examined whether atypical neural responses during mentalizing and self-representation are sex/gender-dependent in autistic adults and explored whether ‘camouflaging’ (acting as if behaviourally neurotypical) is associated with sex/gender-dependent neural responses. In total, N = 119 adults (33 typically developing males, 29 autistic males, 29 typically developing females and 28 autistic females) participated in a task-related functional magnetic resonance imaging paradigm to assess neural activation within right temporo-parietal junction and ventromedial prefrontal cortex during mentalizing and self-representation. Camouflaging in autism was quantified as the discrepancy between extrinsic behaviour in social–interpersonal contexts and intrinsic status. While autistic men showed hypoactive right temporo-parietal junction mentalizing and ventromedial prefrontal cortex self-representation responses compared to typically developing men, such neural responses in autistic women were not different from typically developing women. In autistic women only, increasing camouflaging was associated with heightened ventromedial prefrontal cortex self-representation response. There is a lack of impaired neural self-representation and mentalizing in autistic women compared to typically developing women. Camouflaging is heightened in autistic women and may relate to neural self-representation response. These results reveal brain-behaviour relations that help explain sex/gender-heterogeneity in social brain function in autism.

Do you know what I'm thinking? Temporal and spatial brain activity during a theory-of-mind task in children with autism

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First MEG study of neural underpinnings of theory of mind differences in autism.

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Children with autism show decreased LTPJ activity from 300 to 375 and 425 to 500 ms.

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Children with autism also show increased RIFG activity from 325 to 375 ms.

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Co-incident lower LTPJ and higher RIFG activity implies compensatory use of RIFG.

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Executive functions may augment impaired theory of mind in autism.

The social impairments observed in children with autism spectrum disorder are thought to arise in part from deficits in theory of mind, the ability to understand other people’s thoughts and feelings. To determine the temporal-spatial dynamics of brain activity underlying these atypical theory-of-mind processes, we used magnetoencephalography to characterize the sequence of functional brain patterns (i.e. when and where) related to theory-of-mind reasoning in 19 high-functioning children with autism compared to 22 age- and sex-matched typically-developing children aged 8–12 during a false-belief (theory-of-mind) task. While task performance did not differ between the two groups, children with autism showed reduced activation in the left temporoparietal junction between 300–375 and 425–500 ms, as well as increased activation in the right inferior frontal gyrus from 325 to 375 ms compared to controls. The overlap in decreased temporoparietal junction activity and increased right inferior frontal gyrus activation from 325 to 375 ms suggests that in children with autism, the right inferior frontal gyrus may compensate for deficits in the temporoparietal junction, a neural theory-of-mind network hub. As the right inferior frontal gyrus is involved in inhibitory control, this finding suggests that children with autism rely on executive functions to bolster their false-belief understanding.

Abilities to Explicitly and Implicitly Infer Intentions from Actions in Adults with Autism Spectrum Disorder

Previous research suggests that Autism Spectrum Disorder (ASD) might be associated with impairments on implicit but not explicit mentalizing tasks. However, such comparisons are made difficult by the heterogeneity of stimuli and the techniques used to measure mentalizing capabilities. We tested the abilities of 34 individuals (17 with ASD) to derive intentions from others' actions during both explicit and implicit tasks and tracked their eye-movements. Adults with ASD displayed explicit but not implicit mentalizing deficits. Adults with ASD displayed typical fixation patterns during both implicit and explicit tasks. These results illustrate an explicit mentalizing deficit in adults with ASD, which cannot be attributed to differences in fixation patterns.

Short communication: Sex-linked differences in gamma-aminobutyric acid (GABA) are related to social functioning in autism spectrum disorder

Magnetic resonance spectroscopy (MRS) was utilized to investigate sex differences in gamma-aminobutyric acid (GABA) between adults with autism spectrum disorder (ASD) and neurotypical (NT) controls. GABA at the right superior temporal sulcus (STS) is reported for 12 ASD and 14 NT participants. The results show no group differences in GABA. There was, however, a significant positive association between GABA at the STS and autism-related social impairments in females with ASD. These findings provide preliminary support for sex differences in GABAergic distribution and processes that contribute to social functioning in ASD.

Altered perspective-dependent brain activation while viewing hands and associated imitation difficulties in individuals with autism spectrum disorder

Background

Individuals with autism spectrum disorder (ASD) appear to have a unique awareness of their own body, which may be associated with difficulties of gestural interaction. In typically developing (TD) individuals, the perception of body parts is processed in various brain regions. For instance, activation of the lateral occipito-temporal cortex (LOTC) is known to depend on perspective (i.e., first- or third-person perspective) and identity (i.e., own vs. another person's body). In the present study, we examined how perspective and identity affect brain activation in individuals with ASD, and how perspective- and identity-dependent brain activation is associated with gestural imitation abilities.

Methods

Eighteen young adults with ASD and 18 TD individuals participated in an fMRI study in which the participants observed their own or another person's hands from the first- and third-person perspectives. We examined whether the brain activation associated with perspective and identity was altered in individuals with ASD. Furthermore, we identified the brain regions the activity of which correlated with gestural imitation difficulties in individuals with ASD.

Results

In the TD group, the left LOTC was more strongly activated by viewing a hand from the third-person perspective compared with the first-person perspective. This perspective effect in the left LOTC was significantly attenuated in the ASD group. We also observed significant group differences in the perspective effect in the medial prefrontal cortex (mPFC). Correlation analysis revealed that the perspective effect in the inferior parietal lobule (IPL) and cerebellum was associated with the gestural imitation ability in individuals with ASD.

Conclusions

Our study suggests that atypical visual self-body recognition in individuals with ASD is associated with an altered perspective effect in the LOTC and mPFC, which are thought to be involved in the physical and core selves, respectively. Furthermore, the gestural imitation difficulty in individuals with ASD might be associated with the altered activation in the IPL and cerebellum, but not in the LOTC. These findings shed light on common and divergent neural mechanisms underlying atypical visual self-body awareness and gestural interaction in ASD.

Sex Differences in Autism Spectrum Disorder: a Review

PURPOSE OF REVIEW

Neurodevelopmental disorders disproportionately affect males. The mechanisms underlying male vulnerability or female protection are not known and remain understudied. Determining the processes involved is crucial to understanding the etiology and advancing treatment of neurodevelopmental disorders. Here, we review current findings and theories that contribute to male preponderance of neurodevelopmental disorders, with a focus on autism.

RECENT FINDINGS

Recent work on the biological basis of the male preponderance of autism and other neurodevelopmental disorders includes discussion of a higher genetic burden in females and sex-specific gene mutations or epigenetic changes that differentially confer risk to males or protection to females. Other mechanisms discussed are sex chromosome and sex hormone involvement. Specifically, fetal testosterone is involved in many aspects of development and may interact with neurotransmitter, neuropeptide, or immune pathways to contribute to male vulnerability. Finally, the possibilities of female underdiagnosis and a multi-hit hypothesis are discussed. This review highlights current theories of male bias in developmental disorders. Topics include environmental, genetic, and epigenetic mechanisms; theories of sex chromosomes, hormones, neuroendocrine, and immune function; underdiagnosis of females; and a multi-hit hypothesis.

Changes in brain metabolic connectivity underlie autistic-like social deficits in a rat model of autism spectrum disorder

The neurobiological basis of social dysfunction and the high male prevalence in autism spectrum disorder (ASD) remain poorly understood. Although network alterations presumably underlie the development of autistic-like behaviors, a clear pattern of connectivity differences specific to ASD has not yet emerged. Because the heterogeneous nature of ASD hinders investigations in human subjects, we explored brain connectivity in an etiologically homogenous rat model of ASD induced by exposure to valproic acid (VPA) in utero. We performed partial correlation analysis of cross-sectional resting-state ¹⁸F-fluorodeoxyglucose positron emission tomography scans from VPA-exposed and control rats to estimate metabolic connectivity and conducted canonical correlation analysis of metabolic activity and behavior scores. VPA-treated rats exhibited impairments in social behaviors, and this difference was more pronounced in male than female rats. Similarly, current analyses revealed sex-specific changes in network connectivity and identified distinct alterations in the distributed metabolic activity patterns associated with autistic-like social deficits. Specifically, diminished activity in the salience network and enhanced activity in a cortico-cerebellar circuit correlated with the severity of social behavioral deficits. Such metabolic connectivity features may represent neurobiological substrates of autistic-like behavior, particularly in males, and may serve as a pathognomonic sign in the VPA rat model of ASD.

The Default Mode Network in Autism

Autism spectrum disorder (ASD) is characterized by deficits in social communication and interaction. Since its discovery as a major functional brain system, the default mode network (DMN) has been implicated in a number of psychiatric disorders, including ASD. Here we review converging multimodal evidence for DMN dysfunction in the context of specific components of social cognitive dysfunction in ASD: 'self-referential processing' - the ability to process social information relative to oneself and 'theory of mind' or 'mentalizing' - the ability to infer the mental states such as beliefs, intentions, and emotions of others. We show that altered functional and structural organization of the DMN, and its atypical developmental trajectory, are prominent neurobiological features of ASD. We integrate findings on atypical cytoarchitectonic organization and imbalance in excitatory-inhibitory circuits, which alter local and global brain signaling, to scrutinize putative mechanisms underlying DMN dysfunction in ASD. Our synthesis of the extant literature suggests that aberrancies in key nodes of the DMN and their dynamic functional interactions contribute to atypical integration of information about the self in relation to 'other', as well as impairments in the ability to flexibly attend to socially relevant stimuli. We conclude by highlighting open questions for future research.

Behavioural and cognitive sex/gender differences in autism spectrum condition and typically developing males and females

Studies assessing sex/gender differences in autism spectrum conditions often fail to include typically developing control groups. It is, therefore, unclear whether observed sex/gender differences reflect those found in the general population or are particular to autism spectrum conditions. A systematic search identified articles comparing behavioural and cognitive characteristics in males and females with and without an autism spectrum condition diagnosis. A total of 13 studies were included in meta-analyses of sex/gender differences in core autism spectrum condition symptoms (social/communication impairments and restricted/repetitive behaviours and interests) and intelligence quotient. A total of 20 studies were included in a qualitative review of sex/gender differences in additional autism spectrum condition symptoms. For core traits and intelligence quotient, sex/gender differences were comparable in autism spectrum conditions and typical samples. Some additional autism spectrum condition symptoms displayed different patterns of sex/gender differences in autism spectrum conditions and typically developing groups, including measures of executive function, empathising and systemising traits, internalising and externalising problems and play behaviours. Individuals with autism spectrum conditions display typical sex/gender differences in core autism spectrum condition traits, suggesting that diagnostic criteria based on these symptoms should take into account typical sex/gender differences. However, awareness of associated autism spectrum condition symptoms should include the possibility of different male and female phenotypes, to ensure those who do not fit the 'typical' autism spectrum condition presentation are not missed.

Different aberrant mentalizing networks in males and females with autism spectrum disorders: Evidence from resting-state functional magnetic resonance imaging

Previous studies have found that individuals with autism spectrum disorders show impairments in mentalizing processes and aberrant brain activity compared with typically developing participants. However, the findings are mainly from male participants and the aberrant effects in autism spectrum disorder females and sex differences are still unclear. To address these issues, this study analyzed intrinsic functional connectivity of mentalizing regions using resting-state functional magnetic resonance imaging data of 48 autism spectrum disorder males and females and 48 typically developing participants in autism brain imaging data exchange. Whole-brain analyses showed that autism spectrum disorder males had hyperconnectivity in functional connectivity of the bilateral temporal-parietal junction, whereas autism spectrum disorder females showed hypoconnectivity in functional connectivity of the medial prefrontal cortex, precuneus, and right temporal-parietal junction. Interaction between sex and autism was found in both short- and long-distance functional connectivity effects, confirming that autism spectrum disorder males showed overconnectivity, while autism spectrum disorder females showed underconnectivity. Furthermore, a regression analysis revealed that in autism spectrum disorder, males and females demonstrated different relations between the functional connectivity effects of the mentalizing regions and the core autism spectrum disorder deficits. These results suggest sex differences in the mentalizing network in autism spectrum disorder individuals. Future work is needed to examine how sex interacts with other factors such as age and the sex differences during mentalizing task performance.

Single Pulse Transcranial Magnetic Stimulation-Electroencephalogram Reveals No Electrophysiological Abnormality in Adults with High-Functioning Autism Spectrum Disorder

OBJECTIVE

Neuroimaging and electrophysiological research have revealed a range of neural abnormalities in autism spectrum disorder (ASD), but a comprehensive understanding remains elusive. We utilized a novel methodology among individuals with ASD and matched controls, combining transcranial magnetic stimulation (TMS) with concurrent electroencephalogram (EEG) recording (TMS-EEG) to explore cortical function and connectivity in three sites implicated in the neuropathophysiology of ASD (dorsolateral prefrontal cortex, primary motor cortex, and temporoparietal junction). As there is evidence for neurobiological gender differences in ASD, we also examined the influence of biological sex.

METHODS

TMS pulses were applied to each of the three sites (right lateralized) during 20-channel EEG recording.

RESULTS

We did not identify any differences in the EEG response to TMS between ASD and control groups. This finding remained when data were stratified by sex. Nevertheless, traits and characteristics associated with ASD were correlated with the neurophysiological response to TMS.

CONCLUSION

While TMS-EEG did not appear to clarify the neuropathophysiology of ASD, the relationships identified between the neurophysiological response to TMS and clinical characteristics warrant further investigation.

Speech Discrimination Difficulties in High-Functioning Autism Spectrum Disorder Are Likely Independent of Auditory Hypersensitivity

Autism Spectrum Disorder (ASD), characterized by impaired communication skills and repetitive behaviors, can also result in differences in sensory perception. Individuals with ASD often perform normally in simple auditory tasks but poorly compared to typically developed (TD) individuals on complex auditory tasks like discriminating speech from complex background noise. A common trait of individuals with ASD is hypersensitivity to auditory stimulation. No studies to our knowledge consider whether hypersensitivity to sounds is related to differences in speech-in-noise discrimination. We provide novel evidence that individuals with high-functioning ASD show poor performance compared to TD individuals in a speech-in-noise discrimination task with an attentionally demanding background noise, but not in a purely energetic noise. Further, we demonstrate in our small sample that speech-hypersensitivity does not appear to predict performance in the speech-in-noise task. The findings support the argument that an attentional deficit, rather than a perceptual deficit, affects the ability of individuals with ASD to discriminate speech from background noise. Finally, we piloted a novel questionnaire that measures difficulty hearing in noisy environments, and sensitivity to non-verbal and verbal sounds. Psychometric analysis using 128 TD participants provided novel evidence for a difference in sensitivity to non-verbal and verbal sounds, and these findings were reinforced by participants with ASD who also completed the questionnaire. The study was limited by a small and high-functioning sample of participants with ASD. Future work could test larger sample sizes and include lower-functioning ASD participants.