Sensory Gating in Neurodevelopmental Disorders: A Scoping Review.

This review aimed to explore the current understanding of sensory gating in neurodevelopmental disorders as a possible transdiagnostic mechanism. We applied methods according to the Joanna Briggs Institute Manual for Evidence Synthesis, following the population, concept, and context scoping review eligibility criteria. Using a comprehensive search strategy in five relevant research databases (Medline, EMBASE, CINAHL, PsychInfo, and Scopus), we searched for relevant peer-reviewed, primary research articles and unpublished data. Two independent reviewers screened the titles and abstracts, full-texts, and completed data extraction. We identified a total of 81 relevant articles and used descriptive analyses to summarize the characteristics and outcomes of all identified studies. Literature regarding sensory gating was most common in autistic populations with relatively fewer studies examining attention-deficit/hyperactivity disorder, tic disorders, and childhood-onset fluency disorder (COFD). The methods to assess sensory gating varied widely both within and between groups and included measures such as habituation, prepulse inhibition, affect-modulated inhibition, medication and other intervention trials. Most consistently, when participants complete questionnaires about their sensory experiences, those who have neurodevelopmental disorders report differences in their sensory gating. Affect-modulated inhibition appears to be discrepant between samples with and without neurodevelopmental disorder diagnoses. Habituation was the most commonly reported phenomenon and many differences in habituation have been found in autistic individuals and individuals with tic disorders whereas concerns with inhibition seemed more common in COFD. Overall, the evidence is inconsistent within and between disorders suggesting there is still much to learn about sensory gating in neurodevelopmental disorders.

Closing the species gap: Translational approaches to studying sensory processing differences relevant for autism spectrum disorder.

The study of sensory phenotypes has great potential for increasing research translation between species, a necessity to decipher the neural mechanisms that contribute to higher-order differences in neurological conditions such as autism spectrum disorder (ASD). Over the past decade, despite separate advances in our understanding of the structural and functional differences within the brain of autistic and non-autistic individuals and in rodent models for ASD, researchers have had difficulty translating the findings in murine species to humans, mostly due to incompatibility in experimental methodologies used to screen for ASD phenotypes. Focusing on sensory phenotypes offers an avenue to close the species gap because sensory pathways are highly conserved across species and are affected by the same risk-factors as the higher-order brain areas mostly responsible for the diagnostic criteria for ASD. By first reviewing how sensory processing has been studied to date, we direct our focus to electrophysiological and behavioral techniques that can be used to study sensory phenotypes consistently across species. Using auditory sensory phenotypes as a template, we seek to improve the accessibility of translational methods by providing a framework for collecting cohesive data in both rodents and humans. Specifically, evoked-potentials, acoustic startle paradigms, and psychophysical detection/discrimination paradigms can be created and implemented in a coordinated and systematic fashion across species. Through careful protocol design and collaboration, sensory processing phenotypes can be harnessed to bridge the gap that exists between preclinical animal studies and human testing, so that mutually held questions in autism research can be answered. LAY SUMMARY: It has always been difficult to relate results from animal research to humans. We try to close this gap by studying changes in sensory processing using careful protocol design and collaboration between clinicians and researchers. Sensory pathways are comparable between animals and humans, and are affected in the same way as the rest of the brain in ASD. Using changes in hearing as a template, we point the field in an innovative direction by providing a framework for collecting cohesive data in rodents and humans.

Factor Structure of Repetitive Behaviors Across Autism Spectrum Disorder and Attention-Deficit/Hyperactivity Disorder.

Restricted interests and repetitive behaviors (RRBs) are core symptoms of autism spectrum disorder (ASD), and commonly occur in attention-deficit/hyperactivity disorder (ADHD). Little is known about how RRBs manifest in ADHD. We quantified and compared factor structures of RRBs in children with ASD (n = 634) or ADHD (n = 448), and related factors to sex and IQ. A four-factor solution emerged, including Stereotypy, Self-Injury, Compulsions, and Ritualistic/Sameness. Factor structures were equivalent across diagnoses, though symptoms were more severe in ASD. IQ negatively correlated with Stereotypy, Self-Injury, and Compulsions in ASD, and negatively correlated with Compulsions and Ritualistic/Sameness behaviors in ADHD. In ASD only, females exhibited higher Self-Injury. Thus, patterns of RRBs are preserved across ASD and ADHD, but severity and relationship with IQ differed.

Differentiating between sensory sensitivity and sensory reactivity in relation to restricted interests and repetitive behaviours.

Recent studies have suggested that individuals who exhibit heightened sensitivity also exhibit higher rates and severity of restricted interests and repetitive behaviours. This line of research has been conducted almost exclusively through caregiver reports of sensitivity. Here, a more rigorous psychophysics paradigm was applied to assess sensory sensitivity and relate hypersensitivity to restricted interests and repetitive behaviours. In addition, commonly used questionnaire measures of sensory sensitivity were collected to determine if self-reported measures accurately reflect behavioural measures of sensory sensitivity. In all, 90 typically developing participants completed a visual detection task, a questionnaire measure of sensory processing and a measure of restricted interests and repetitive behaviours. Visual sensitivity, measured both behaviourally and with questionnaires, is positively related to restricted interests and repetitive behaviours. Surprisingly, visual sensitivity as measured behaviourally and through self-report are unrelated. Furthermore, a regression analysis suggests that while restricted interests and repetitive behaviours can be predicted based on both behavioural and self-reported sensitivity, these two predictors account for different portions of the variance in restricted interests and repetitive behaviours. Thus, while these results provide evidence supporting the contribution of sensory sensitivity to restricted interests and repetitive behaviours, these results also indicate that behavioural and questionnaire measures of sensory sensitivity are measuring two distinct constructs. We hypothesize that behavioural measures are measuring sensory sensitivity, while questionnaires measures are in fact measuring sensory reactivity.

Sensory hypersensitivity predicts repetitive behaviours in autistic and typically-developing children.

The objective of this study was to examine the relationship between sensory hypersensitivity and restricted interests and repetitive behaviours associated with autism spectrum disorder and their typically-developing peers. Furthermore, the aims included the examination of the relationship across sensory modalities and various types of restricted interests and repetitive behaviours. Data were collected from the parents of 114 children: 49 of whom were diagnosed with autism spectrum disorder and 65 typically-developing children. Parents completed the Sensory Profile 2 - Child Version and the Repetitive Behaviours Questionnaire, Second Edition. The results suggested that sensory hypersensitivity is strongly related to the core autism spectrum disorder symptom of repetitive behaviours. This relationship was not specific to autism spectrum disorder; repetitive behaviours significantly increased with sensory hypersensitivity in typically-developing individuals as well. This effect was consistent across all modalities in both autism spectrum disorder and typically developing groups; group differences were observed in the oral and tactile modalities. Furthermore, sensory hypersensitivity was significantly predictive of repetitive behaviours in all participants, autism spectrum disorder and typically-developing, and importantly, autism spectrum disorder diagnosis did not add any predictive influence above and beyond sensory hypersensitivity. Finally, sensory hypersensitivity was significantly predictive of all subdomains of repetitive behaviours, including repetitive motor movements, rigidity and adherence to routine, preoccupation with restricted patterns of interest and unusual sensory interests, and diagnosis added no predictive ability beyond sensory hypersensitivity.

Increases in the autistic trait of attention to detail are associated with decreased multisensory temporal adaptation.

Recent empirical evidence suggests that autistic individuals perceive the world differently than their typically-developed peers. One theoretical account, the predictive coding hypothesis, posits that autistic individuals show a decreased reliance on previous perceptual experiences, which may relate to autism symptomatology. We tested this through a well-characterized, audiovisual statistical-learning paradigm in which typically-developed participants were first adapted to consistent temporal relationships between audiovisual stimulus pairs (audio-leading, synchronous, visual-leading) and then performed a simultaneity judgement task with audiovisual stimulus pairs varying in temporal offset from auditory-leading to visual-leading. Following exposure to the visual-leading adaptation phase, participants' perception of synchrony was biased towards visual-leading presentations, reflecting the statistical regularities of their previously experienced environment. Importantly, the strength of adaptation was significantly related to the level of autistic traits that the participant exhibited, measured by the Autism Quotient (AQ). This was specific to the Attention to Detail subscale of the AQ that assesses the perceptual propensity to focus on fine-grain aspects of sensory input at the expense of more integrative perceptions. More severe Attention to Detail was related to weaker adaptation. These results support the predictive coding framework, and suggest that changes in sensory perception commonly reported in autism may contribute to autistic symptomatology.