Disentangling global and domain-level adaptive behavior trajectories among children with autism spectrum disorder.

BACKGROUND: Heterogeneity in adaptive behavior abilities among people with autism spectrum disorder (ASD) is expressed not only as uneven levels of impairment across domains, but also in the developmental trajectories of adaptive skills. We studied the question of whether, after accounting for global adaptive behavior development, we find evidence of heterogeneity in the trajectories of specific domains of adaptive behavior. METHODS: A sample of 504 children with ASD was obtained by combining data from two independent natural history studies conducted in North America. We used a factor of curves model to explain growth between 36 and 138 months in Vineland Adaptive Behavior Scales, Second Edition (VABS) age equivalents as a function of domain-specific and global growth processes. RESULTS: The domain-specific trajectories in all three domains (Communication, Daily Living Skills, and Socialization) reflected impairment relative to age expectations as well as slower-than-expected growth with age, and the parameters of these trajectories were moderately-to-strongly correlated across domains. The global adaptive behavior trajectory had an initial (36-41 months of age) developmental level of about 22 age-equivalent months, and eventually slowed after initially increasing by about 6 months each year. The global trajectory accounted for the majority of variance in the domain-level processes; however, additional variance remained (14%-38%) in the domain-level intercepts, slopes, and quadratic processes. CONCLUSIONS: These results extend existing theoretical and empirical support for the hierarchical structure of adaptive behavior to include its development over time in clinical samples of children with ASD. A latent global trajectory may be sufficient to describe the growth of adaptive behavior in children with ASD; however, the remaining domain-specific variability after accounting for global adaptive behavior development allows for the possibility that differential effects of intervention on specific domains may be possible and detectable.

Prerequisite Skills in Cognitive Testing: Innovations in theory and recommendations for practice.

Testing cognitive skill development is important for diagnostic, prognostic, and monitoring purposes, especially for young children and individuals with neurodevelopmental disorders. Developmental tests have been created for infants and toddlers, while traditional IQ tests are often employed beginning in the later preschool period. However, IQ tests rely on developmental skills that are rapidly changing during early childhood. Here, we introduce the idea of prerequisite skills in developmental domains, which are discrete skills required for, but not explicitly tested by, traditional IQ tests. Focusing on general cognition, particularly among children with a chronological or mental age under 4 years, may fail to capture important nuances in skill development. New skill-based assessments are needed in general, and in particular for categorization, which is foundational to higher-order cognitive skills. Novel measures quantifying categorization skills would provide a more sensitive measure of development for young children and older individuals with low developmental levels.

Functional near-infrared spectroscopy in toddlers: Neural differentiation of communicative cues and relation to future language abilities.

The toddler and preschool years are a time of significant development in both expressive and receptive communication abilities. However, little is known about the neurobiological underpinnings of language development during this period, likely due to difficulties acquiring functional neuroimaging data. Functional near-infrared spectroscopy (fNIRS) is a motion-tolerant neuroimaging technique that assesses cortical brain activity and can be used in very young children. Here, we use fNIRS during perception of communicative and noncommunicative speech and gestures in typically developing 2- and 3-year-olds (Study 1, n = 15, n = 12 respectively) and in a sample of 2-year-olds with both fNIRS data collected at age 2 and language outcome data at age 3 (Study 2, n = 18). In Study 1, 2- and 3-year-olds differentiated between communicative and noncommunicative stimuli as well as between speech and gestures in the left lateral frontal region. However, 2-year-olds showed different patterns of activation from 3-year-olds in right medial frontal regions. In Study 2, which included two toddlers identified with early language delays along with 16 typically developing toddlers, neural differentiation of communicative stimuli in the right medial frontal region at age 2 predicted receptive language at age 3. Specifically, after accounting for variance related to verbal ability at age 2, increased neural activation for communicative gestures (vs. both communicative speech and noncommunicative gestures) at age 2 predicted higher receptive language scores at age 3. These results are discussed in the context of the underlying mechanisms of toddler language development and use of fNIRS in prediction of language outcomes.

Developmental Associations between Cognition and Adaptive Behavior in Intellectual and Developmental Disability.

Background: Intellectual and developmental disabilities (IDDs) are associated with both cognitive challenges and difficulties in conceptual, social, and practical areas of living (DSM-5). Individuals with IDD often present with an intellectual disability in addition to a developmental disability such as autism or Down syndrome. Those with IDD may present with deficits in intellectual functioning as well as adaptive functioning that interfere with independence and living skills. The present study sought to examine associations of longitudinal developmental change in domains of cognition (NIH Toolbox Cognition Battery, NIHTB-CB) and adaptive behavior domains (Vineland Adaptive Behavior Scales-3; VABS-3) including Socialization, Communication, and Daily Living Skills (DLS) over a two-year period. Methods: Eligible participants for this multisite longitudinal study included those who were between 6 and 26 years at Visit 1, and who had a diagnosis of, or suspected intellectual disability (ID), including borderline ID. Three groups were recruited, including those with fragile X syndrome, Down syndrome, and other/idiopathic intellectual disability. In order to examine the association of developmental change between cognitive and adaptive behavior domains, bivariate latent change score (BLCS) models were fit to compare change in the three cognitive domains measured by the NIHTB-CB (Fluid, Crystallized, Composite) and the three adaptive behavior domains measured by the VABS-3 (Communication, DLS, and Socialization). Results: Over a two-year period, change in cognition (both Crystalized and Composite) was significantly and positively associated with change in daily living skills. Also, baseline cognition level predicted growth in adaptive behavior, however baseline adaptive behavior did not predict growth in cognition in any model. Conclusions: The present study demonstrated that developmental improvements in cognition and adaptive behavior are associated in children and young adults with IDD, indicating the potential for cross-domain effects of intervention. Notably, improvements in Daily Living Skills on the VABS-3 emerged as a primary area of adaptive behavior that positively related to improvements in cognition. This work provides evidence for the clinical, "real life" meaningfulness of the NIHTB-CB in IDD, and important empirical support for the NIHTB-CB as a fit-for-purpose performance-based outcome measure for this population.

Developmental associations between cognition and adaptive behavior in intellectual and developmental disability.

BACKGROUND: Intellectual and developmental disabilities (IDDs) are associated with both cognitive challenges and difficulties in conceptual, social, and practical areas of living, commonly referred to as adaptive behavior (DSM-5). Although cross-sectional associations between intelligence or cognition and adaptive behavior have been reported in IDD populations, no study to date has examined whether developmental changes in cognition contribute to or track with changes in adaptive behavior. The present study sought to examine associations of longitudinal developmental change in domains of cognition (NIH Toolbox Cognition Battery, NIHTB-CB) and adaptive behavior domains (Vineland Adaptive Behavior Scales-3; VABS-3) including Socialization, Communication, and Daily Living Skills (DLS) over a two year period in a large sample of children, adolescents and young adults with IDD. METHODS: Three groups were recruited, including those with fragile X syndrome, Down syndrome, and other/idiopathic intellectual disability. Eligible participants (n = 263) included those who were between 6 and 26 years (mage = 15.52, sd = 5.17) at Visit 1, and who had a diagnosis of, or suspected intellectual disability (ID), including borderline ID, with a mental age of at least 3.0 years. Participants were given cognitive and adaptive behavior assessments at two time points over a two year period (m = 2.45 years, range = 1.27 to 5.56 years). In order to examine the association of developmental change between cognitive and adaptive behavior domains, bivariate latent change score (BLCS) models were fit to compare change in the three cognitive domains measured by the NIHTB-CB (Fluid Cognition, Crystallized Cognition, Total Cognition) and the three adaptive behavior domains measured by the VABS-3 (Communication, DLS, and Socialization). RESULTS: Over a two year period, change in cognition (both Crystallized and Total Composites) was significantly and positively associated with change in daily living skills. Also, baseline cognition level predicted growth in adaptive behavior, however baseline adaptive behavior did not predict growth in cognition in any model. CONCLUSIONS: The present study demonstrated that developmental changes in cognition and adaptive behavior are associated in children and young adults with IDD, indicating the potential for cross-domain effects of intervention. Notably, improvements in DLS emerged as a primary area of adaptive behavior that positively related to improvements in cognition. This work provides evidence for the clinical, "real life" meaningfulness of changes in cognition detected by the NIHTB-CB in IDD, and provides empirical support for the NIHTB-CB as a fit-for-purpose performance-based outcome measure for this population.

How do 3-year-olds do on the NIH Toolbox Cognitive Battery?

The NIH Toolbox includes a cognitive battery that provides an Early Childhood Composite score for children age 3-7. However, very few studies have evaluated feasibility when it is used in the youngest segment of this age range-3-year-olds. The current study evaluated performance on the four cognitive subtests composing the early childhood composite, two of which assess executive function, in a large sample of 3-year-olds enrolled in a Vanguard pilot of the National Children's Study. Results found that in a cohort of 609 3-year-olds (mean age = 39.6 months, SD = 1.6, 53% male, 64% White, 87% Non-Hispanic) who were administered four subtests included in the Early Childhood Composite, up to approximately 30% were unable to pass practice items on the Flanker, Dimensional Change Card Sort, and Picture Sequence Memory, whereas only approximately 3% were unable to pass practice items on the Picture Vocabulary Test. Furthermore, of those that did pass practice and achieve scores on the subtests, approximately 70% and 80% performed at or below chance level on the executive function tasks (Flanker and Dimensional Change Card Sort) and Picture Sequence Memory, respectively. Ultimately, the average 3-year-old has difficulty with three of the four NIH Toolbox tasks composing the Early Childhood Composite and may not yet have developed the requisite skills. These findings indicate that changes compatible with the developmental level of preschoolers are recommended to increase the feasibility and effectiveness of the NIH Toolbox in measuring individual cognition differences in 3-year-old children.

Simultaneous multimodal fNIRS-EEG recordings reveal new insights in neural activity during motor execution, observation, and imagery.

Motor execution, observation, and imagery are important skills used in motor learning and rehabilitation. The neural mechanisms underlying these cognitive-motor processes are still poorly understood. We used a simultaneous recording of functional near-infrared spectroscopy (fNIRS) and electroencephalogram (EEG) to elucidate the differences in neural activity across three conditions requiring these processes. Additionally, we used a new method called structured sparse multiset Canonical Correlation Analysis (ssmCCA) to fuse the fNIRS and EEG data and determine the brain regions of neural activity consistently detected by both modalities. Unimodal analyses revealed differentiated activation between conditions; however, the activated regions did not fully overlap across the two modalities (fNIRS: left angular gyrus, right supramarginal gyrus, as well as right superior and inferior parietal lobes; EEG: bilateral central, right frontal, and parietal). These discrepancies might be because fNIRS and EEG detect different signals. Using fused fNIRS-EEG data, we consistently found activation over the left inferior parietal lobe, superior marginal gyrus, and post-central gyrus during all three conditions, suggesting that our multimodal approach identifies a shared neural region associated with the Action Observation Network (AON). This study highlights the strengths of using the multimodal fNIRS-EEG fusion technique for studying AON. Neural researchers should consider using the multimodal approach to validate their findings.

NIH Toolbox Cognition Battery Feasibility in Individuals With Williams Syndrome.

The NIH Toolbox Cognition Battery (NIHTB-CB) was developed for epidemiological and longitudinal studies across a wide age span. Such a tool may be useful for intervention trials in conditions characterized by intellectual disability (ID), such as Williams syndrome (WS). Three NIHTB-CB tasks, including two executive functioning (Flanker, Dimensional Change Card Sort) and one episodic memory (Picture Sequence Memory) task, were given to 47 individuals with WS, ages 4 to 50, to evaluate feasibility (i.e., proportion of valid administrations) in this population. Findings indicated that NIHTB-CB tests showed good feasibility. Flanker and DCCS age-corrected scores were negatively correlated with age and showed floor effects, indicating these scores may not be useful for quantifying performance on these NIHTB-CB tests in ID.

Structured sparse multiset canonical correlation analysis of simultaneous fNIRS and EEG provides new insights into the human action-observation network.

The action observation network (AON) is a network of brain regions involved in the execution and observation of a given action. The AON has been investigated in humans using mostly electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI), but shared neural correlates of action observation and action execution are still unclear due to lack of ecologically valid neuroimaging measures. In this study, we used concurrent EEG and functional Near Infrared Spectroscopy (fNIRS) to examine the AON during a live-action observation and execution paradigm. We developed structured sparse multiset canonical correlation analysis (ssmCCA) to perform EEG-fNIRS data fusion. MCCA is a generalization of CCA to more than two sets of variables and is commonly used in medical multimodal data fusion. However, mCCA suffers from multi-collinearity, high dimensionality, unimodal feature selection, and loss of spatial information in interpreting the results. A limited number of participants (small sample size) is another problem in mCCA, which leads to overfitted models. Here, we adopted graph-guided (structured) fused least absolute shrinkage and selection operator (LASSO) penalty to mCCA to conduct feature selection, incorporating structural information amongst the variables (i.e., brain regions). Benefitting from concurrent recordings of brain hemodynamic and electrophysiological responses, the proposed ssmCCA finds linear transforms of each modality such that the correlation between their projections is maximized. Our analysis of 21 right-handed participants indicated that the left inferior parietal region was active during both action execution and action observation. Our findings provide new insights into the neural correlates of AON which are more fine-tuned than the results from each individual EEG or fNIRS analysis and validate the use of ssmCCA to fuse EEG and fNIRS datasets.

Using Functional Connectivity to Examine the Correlation between Mirror Neuron Network and Autistic Traits in a Typically Developing Sample: A fNIRS Study.

Mirror neuron network (MNN) is associated with one's ability to recognize and interpret others' actions and emotions and has a crucial role in cognition, perception, and social interaction. MNN connectivity and its relation to social attributes, such as autistic traits have not been thoroughly examined. This study aimed to investigate functional connectivity in the MNN and assess relationship between MNN connectivity and subclinical autistic traits in neurotypical adults. Hemodynamic responses, including oxy- and deoxy-hemoglobin were measured in the central and parietal cortex of 30 healthy participants using a 24-channel functional Near-Infrared spectroscopy (fNIRS) system during a live action-observation and action-execution task. Functional connectivity was derived from oxy-hemoglobin data. Connections with significantly greater connectivity in both tasks were assigned to MNN connectivity. Correlation between connectivity and autistic traits were performed using Pearson correlation. Connections within the right precentral, right supramarginal, left inferior parietal, left postcentral, and between left supramarginal-left angular regions were identified as MNN connections. In addition, individuals with higher subclinical autistic traits present higher connectivity in both action-execution and action-observation conditions. Positive correlation between MNN connectivity and subclinical autistic traits can be used in future studies to investigate MNN in a developing population with autism spectrum disorder.

Comparison of Functional Connectivity in the Prefrontal Cortex during a Simple and an Emotional Go/No-Go Task in Female versus Male Groups: An fNIRS Study.

Inhibitory control is a cognitive process to suppress prepotent behavioral responses to stimuli. This study aimed to investigate prefrontal functional connectivity during a behavioral inhibition task and its correlation with the subject's performance. Additionally, we identified connections that are specific to the Go/No-Go task. The experiment was performed on 42 normal, healthy adults who underwent a vanilla baseline and a simple and emotional Go/No-Go task. Cerebral hemodynamic responses were measured in the prefrontal cortex using a 16-channel near infrared spectroscopy (NIRS) device. Functional connectivity was calculated from NIRS signals and correlated to the Go/No-Go performance. Strong connectivity was found in both the tasks in the right hemisphere, inter-hemispherically, and the left medial prefrontal cortex. Better performance (fewer errors, faster response) is associated with stronger prefrontal connectivity during the simple Go/No-Go in both sexes and the emotional Go/No-Go connectivity in males. However, females express a lower emotional Go/No-Go connectivity while performing better on the task. This study reports a complete prefrontal network during a simple and emotional Go/No-Go and its correlation with the subject's performance in females and males. The results can be applied to examine behavioral inhibitory control deficits in population with neurodevelopmental disorders.

A novel measure of matching categories for early development: Item creation and pilot feasibility study.

BACKGROUND: Many cognitive tests assess a limited developmental span, making longitudinal measurement for trials aimed at improving cognition challenging. Tests targeting transitional skills, which integrate foundational abilities into complex schemas, may be amenable to assessment across a wide developmental span. Furthermore, tablet-based tests permit computer adaptive testing (CAT), which is psychometrically more efficient and could increase testing motivation, especially for children with developmental delays. Such measures may be useful for research and clinical practice. AIMS: Outline the creation of a novel, tablet-based concept formation test, and evaluate its feasibility in individuals with mental ages less than 24-months. METHODS AND PROCEDURES: Item generation, user interface construction, and pre-piloting were conducted in consultation with subject matter experts. Item content and interface parameters underwent iterative revisions, resulting in the pilot test. OUTCOMES AND RESULTS: We created and piloted a tablet-based test of concept formation suitable for CAT-based administration with items of increasing difficulty based on target salience. We show feasibility in individuals with mental ages less than 24-months-old. CONCLUSIONS AND IMPLICATIONS: Tablet-based assessment of concept formation may be a useful outcome measure of an aspect of cognitive ability in young children. Future work will address optimizing the user interface and developing CAT administration.

Characterizing the Action-Observation Network Through Functional Near-Infrared Spectroscopy: A Review.

Functional near-infrared spectroscopy (fNIRS) is a neuroimaging technique that has undergone tremendous growth over the last decade due to methodological advantages over other measures of brain activation. The action-observation network (AON), a system of brain structures proposed to have "mirroring" abilities (e.g., active when an individual completes an action or when they observe another complete that action), has been studied in humans through neural measures such as fMRI and electroencephalogram (EEG); however, limitations of these methods are problematic for AON paradigms. For this reason, fNIRS is proposed as a solution to investigating the AON in humans. The present review article briefly summarizes previous neural findings in the AON and examines the state of AON research using fNIRS in adults. A total of 14 fNIRS articles are discussed, paying particular attention to methodological choices and considerations while summarizing the general findings to aid in developing better protocols to study the AON through fNIRS. Additionally, future directions of this work are discussed, specifically in relation to researching AON development and potential multimodal imaging applications.

Parent-reported measure of repetitive behavior in Phelan-McDermid syndrome.

BACKGROUND: Phelan McDermid syndrome (PMS) is a neurogenetic condition associated with a high prevalence of intellectual disability (ID) and autism spectrum disorder (ASD). This study provides a more comprehensive and quantitative profile of repetitive behaviors within the context of ID seen with the condition. METHODS: Individuals age 3-21 years with a confirmed PMS diagnosis participated in a multicenter observational study evaluating the phenotype and natural history of the disorder. We evaluated data collected from this study pertaining to repetitive behaviors from the Repetitive Behavior Scales-Revised (RBS-R). RESULTS: There were n = 90 participants who were part of this analysis. Forty-seven percent (n = 42/90) were female, and the average age at baseline evaluation was 8.88 ± 4.72 years. The mean best estimate IQ of the cohort was 26.08 ± 17.67 (range = 3.4-88), with n = 8 with mild ID (or no ID), n = 20 with moderate ID, and n = 62 with severe-profound ID. The RBS-R total overall score was 16.46 ± 13.9 (compared to 33.14 ± 20.60 reported in previous studies of ASD) (Lam and Aman, 2007), and the total number of items endorsed was 10.40 ± 6.81 (range = 0-29). After statistical correction for multiple comparisons, IQ correlated with the RBS-R stereotypic behavior subscale score (rs = - 0.33, unadjusted p = 0.0014, adjusted p = 0.01) and RBS-R stereotypic behavior total number of endorsed items (rs = - 0.32, unadjusted p = 0.0019, adjusted p = 0.01). IQ did not correlate with any other RBS-R subscale scores. CONCLUSIONS: The RBS-R total overall score in a PMS cohort appears milder compared to individuals with ASD characterized in previous studies. Stereotypic behavior in PMS may reflect cognitive functioning.

Cerebral hemodynamic response during a live action-observation and action-execution task: A fNIRS study.

Although many studies have examined the location of the action observation network (AON) in human adults, the shared neural correlates of action-observation and action-execution are still unclear partially due to lack of ecologically valid neuroimaging measures. In this study, we aim to demonstrate the feasibility of using functional near infrared spectroscopy (fNIRS) to measure the neural correlates of action-observation and action execution regions during a live task. Thirty adults reached for objects or observed an experimenter reaching for objects while their cerebral hemodynamic responses including oxy-hemoglobin (HbO) and deoxy-hemoglobin (HbR) were recorded in the sensorimotor and parietal regions. Our results indicated that the parietal regions, including bilateral superior parietal lobule (SPL), bilateral inferior parietal lobule (IPL), right supra-marginal region (SMG) and right angular gyrus (AG) share neural activity during action-observation and action-execution. Our findings confirm the applicability of fNIRS for the study of the AON and lay the foundation for future work with developmental and clinical populations.

Probing Neurovisceral Integration via Functional Near-Infrared Spectroscopy and Heart Rate Variability.

The neurovisceral integration model (NVM) proposes that an organism's ability to flexibly adapt to its environment is related to biological flexibility within the central autonomic network (CAN). One important aspect of this flexibility is behavioral inhibition (Thayer and Friedman, 2002). During a behavioral inhibition task, the CAN, which comprises a series of feedback loops, must be able to integrate information and react to these inputs flexibly to facilitate optimal performance. The functioning of the CAN is shown to be associated with respiratory sinus arrhythmia (RSA), as the vagus nerve is part of this feedback system. Although the NVM has been examined through neural imaging and RSA, only a few studies have examined these measures simultaneously during the neuroimaging procedure. Furthermore, these studies were done at rest or used tasks that were not targeted at processes associated with the NVM, such as behavioral inhibition and cognitive flexibility. For this reason, the present study assessed RSA and neural activation in the pre-frontal cortex simultaneously while participants completed a behavior inhibition task. RSA and functional near-infrared spectroscopy were collected in 38 adults, and resting levels of pre-frontal activation were negatively related to RSA, but pre-frontal activation during the behavior inhibition task was not. The negative relationship between RSA and oxygenated hemoglobin is consistent with previous functional magnetic resonance imaging work examining the NVM at baseline and should be further studied. Additional research investigating how this relationship may change based on task demands or environmental contexts would help clarify the applicability of the model.

Restricted repetitive behaviors in autism spectrum disorder: A systematic review from the neurovisceral integration perspective.

The neurovisceral integration model posits that cognitive-behavioral inflexibility arises from biological inflexibility of feedback loops within the central autonomic network. The parasympathetic nervous system (PNS) is integral in this network. Activity of the PNS, which is normally tonically inhibited, can be indexed through respiratory sinus arrhythmia (RSA). When the PNS becomes disinhibited, indicating decreased flexibility within the network, RSA is reduced and cognitive-behavioral flexibility is impaired. Using this theoretical framework, cognitive-behavioral inflexibility is discussed from the Research Domain Criteria (RDoC) perspective. Restricted repetitive behaviors in autism spectrum disorder (ASD) are proposed as exemplars of cognitive-behavioral inflexibility, and behavioral and RSA literature in ASD are reviewed. RSA differences and their relation to inflexibility in ASD are discussed to support the model and to propose RSA as a biomarker for cognitive-behavioral inflexibility. Considerations for future research are discussed, in addition to implications the model might have on assessment and transdiagnostic treatment practices.

Maternal Affect During a Challenging Mother-Child Interaction: The Effects of Broad Autism Phenotype and Respiratory Sinus Arrhythmia Reactivity in Mothers of Children With and Without Autism Spectrum Disorder.

Respiratory sinus arrhythmia (RSA) is proposed to index cognitive and behavioral inflexibility. Broad autism phenotype (BAP) traits are prevalent in family members of children with autism spectrum disorder (ASD). The study investigated whether RSA and BAP traits in mothers of typically developing (TD) children and mothers of children with ASD influence maternal affect. It was hypothesized that these factors would interact to influence mother-child interactions. Twenty-three mother-child dyads participated in a challenging interaction while measuring mother's RSA. Results indicated that mothers of children with ASD show different RSA reactivity than mothers of TD children. Furthermore, preliminary analyses revealed RSA reactivity moderated the relationship between mothers' rigidity and maternal affect during this interaction. Implications for future research and interventions are discussed.

Gender differences in restricted and repetitive behaviors and interests in youth with autism.

Previous work has found gender differences in restricted and repetitive behaviors and interests (RRBI) for autism spectrum disorder (ASD). Compared to girls, affected boys have increased stereotyped and restricted behaviors; however much less is known about gender differences in other areas of RRBI. This study aims to identify whether specific RRBI (i.e., stereotyped, self-injurious, compulsive, insistence on sameness, ritualistic, and restricted), as measured by item-level data on the Repetitive Behavior Scale-Revised (RBS-R), can distinguish girls from boys with ASD. Participants included 615 individuals with ASD (507 boys; 82.4%), ages 3-18 years of age (M = 10.26, SD = 4.20), who agreed to share data with the National Database for Autism Research (NDAR). Multivariate analysis of variance and discriminant function analysis (DFA) were used to determine whether item-level RBS-R data could correctly classify cases by gender. DFA results suggest that RBS-R items significantly differentiate gender. Strongly differentiating RBS-R items had greater success in correctly classifying affected boys (67.90%) than girls (61.00%). Items that best-discriminated gender were heightened stereotyped behaviors and restricted interests items in boys and compulsive, sameness, restricted, and self-injurious behavior items in girls. This study is the first to find that girls with ASD may have increased compulsive, sameness, and restricted RRBI compared to boys. Additionally, findings support heightened self-injurious behaviors in affected girls. Future research should disentangle whether elevated rates of RRBI in girls are central to the presentation of ASD in girls or an epiphenomenon of the high rates of co-occurring disorders (e.g., anxiety) noted in girls. Autism Res 2019, 12: 274-283 © 2018 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: This study is the first to examine a comprehensive measure of repetitive behavior in children with autism, with findings of increased compulsive, insistence on sameness, and self-injurious behavior characterizing girls and increased stereotyped and restricted behavior characterizing boys. Future research should determine whether these elevated behaviors in girls are directly part of the autism presentation in girls or symptoms of co-occurring psychopathology. It is important for autism diagnostic measures to best capture the types of repetitive behavior girls may demonstrate.

Respiratory Sinus Arrhythmia Predicts Restricted Repetitive Behavior Severity.

In addition to social communication deficits, restricted repetitive behaviors (RRBs) are a key diagnostic feature of autism spectrum disorder (ASD). Dysfunction of the autonomic nervous system (ANS) in ASD has been posited as a mechanism of RRBs; however, most studies investigating ANS activity in ASD have focused on its relation to social functioning. This study used respiratory sinus arrhythmia (RSA) patterns to measure ANS functioning and analyze its relation to RRBs in children with and without an ASD diagnosis. Baseline RSA and RSA reactivity predicted RRB severity and exploratory analyses revealed these measures may be associated with RRB subgroups. These results are discussed in regards to the behavioral literature on RRBs and the benefits of finding biomarkers for these behaviors.