Elevated Thresholds for Light Touch in Children With Autism Reflect More Conservative Perceptual Decision-Making Rather Than a Sensory Deficit

Sensory Phenotypes in Autism: Making a Case for the Inclusion of Sensory Integration Functions

Sensory features are part of the diagnostic criteria for autism and include sensory hypo/hyper reactivity and unusual sensory interest; however, additional sensory differences, namely differences in sensory integration, have not been routinely explored. This study characterized sensory integration differences in a cohort of children (n = 93) with a confirmed diagnosis of autism (5-9 years) using a standardized, norm-referenced battery. Mean z scores, autism diagnostic scores, and IQ are reported. Participants showed substantial deficits in tactile perception, praxis, balance, visual perception, and visual-motor skills. Relationship with autism diagnostic test scores were weak or absent. Findings suggest additional sensory difficulties that are not typically assessed or considered when characterizing sensory features in autism. These data have implications for a greater understanding of the sensory features in the autism phenotype and the development of personalized treatments.

A working taxonomy for describing the sensory differences of autism

BACKGROUND

Individuals on the autism spectrum have been long described to process sensory information differently than neurotypical individuals. While much effort has been leveraged towards characterizing and investigating the neurobiology underlying the sensory differences of autism, there has been a notable lack of consistency in the terms being used to describe the nature of those differences.

MAIN BODY

We argue that inconsistent and interchangeable terminology-use when describing the sensory differences of autism has become problematic beyond mere pedantry and inconvenience. We begin by highlighting popular terms that are currently being used to describe the sensory differences of autism (e.g. "sensitivity", "reactivity" and "responsivity") and discuss why poor nomenclature may hamper efforts towards understanding the aetiology of sensory differences in autism. We then provide a solution to poor terminology-use by proposing a hierarchical taxonomy for describing and referring to various sensory features.

CONCLUSION

Inconsistent terminology-use when describing the sensory features of autism has stifled discussion and scientific understanding of the sensory differences of autism. The hierarchical taxonomy proposed was developed to help resolve lack of clarity when discussing the sensory differences of autism and to place future research targets at appropriate levels of analysis.

Antivax attitude in the general population along the autism-schizophrenia continuum and the impact of socio-demographic factors

Introduction

One of the most important inventions in human history is vaccines. However, to date a consistent amount of people exhibit a hesitant approach toward them and mixed results have emerged in the attempt to characterize which factors may play a role in predicting such negative attitude. Here, we aimed at investigating how the individual scoring along the autism-schizophrenic continuum component and socio-cultural factors contribute toward vaccination attitudes in the general population.

Methods

To test whether individual position along the autism-schizophrenic continuum could predict vaccine attitude, we used principal component analysis (PCA) to extract the component showing diametric loading between the Schizotypal Personality Questionnaire (SPQ) and Autistic Quotient (AQ) subscales. Then, we performed a series of multiple linear regression analyses to understand the relation between the ASD-SSD continuum component and Vax scores. We also included socio-demographic factors (i.e., gender, education level, and age) as predictors.

Results

Multiple regression analysis revealed that the closer the individual lied on the positive schizotypal pole, the higher was their negative attitude toward vaccines. A diametric, more favorable disposition was found for individuals closer to the autistic end of the continuum. Furthermore, we reported that among the socio-cultural factors, only age can be considered a significant predictor of vaccination attitudes, with younger participants showing a more positive attitudes toward vaccination, while the level of education is an important protective factor in mitigating the negative impact that the proximity to the SSD pole and age play against vaccination disposition.

Discussion

These findings are relevant to improve targeted public health interventions, highlighting the crucial role of demographic, psychological, and social correlates in predicting anti-vax beliefs, which have the devasting potential to increase the spread of infectious disease.

A Multidimensional Investigation of Sensory Processing in Autism: Parent- and Self-Report Questionnaires, Psychophysical Thresholds, and Event-Related Potentials in the Auditory and Somatosensory Modalities

Background

Reconciling results obtained using different types of sensory measures is a challenge for autism sensory research. The present study used questionnaire, psychophysical, and neurophysiological measures to characterize autistic sensory processing in different measurement modalities.

Methods

Participants were 46 autistic and 21 typically developing 11- to 14-year-olds. Participants and their caregivers completed questionnaires regarding sensory experiences and behaviors. Auditory and somatosensory event-related potentials (ERPs) were recorded as part of a multisensory ERP task. Auditory detection, tactile static detection, and tactile spatial resolution psychophysical thresholds were measured.

Results

Sensory questionnaires strongly differentiated between autistic and typically developing individuals, while little evidence of group differences was observed in psychophysical thresholds. Crucially, the different types of measures (neurophysiological, psychophysical, questionnaire) appeared to be largely independent of one another. However, we unexpectedly found autistic participants with larger auditory Tb ERP amplitudes had reduced hearing acuity, even though all participants had hearing acuity in the non-clinical range.

Limitations

The autistic and typically developing groups were not matched on cognitive ability, although this limitation does not affect our main analyses regarding convergence of measures within autism.

Conclusion

Overall, based on these results, measures in different sensory modalities appear to capture distinct aspects of sensory processing in autism, with relatively limited convergence between questionnaires and laboratory-based tasks. Generally, this might reflect the reality that laboratory tasks are often carried out in controlled environments without background stimuli to compete for attention, a context which may not closely resemble the busier and more complex environments in which autistic people's atypical sensory experiences commonly occur. Sensory questionnaires and more naturalistic laboratory tasks may be better suited to explore autistic people's real-world sensory challenges. Further research is needed to replicate and investigate the drivers of the unexpected association we observed between auditory Tb ERP amplitudes and hearing acuity, which could represent an important confound for ERP researchers to consider in their studies.

Predictive waves in the autism-schizophrenia continuum: A novel biobehavioral model

The brain is a predictive machine. Converging data suggests a diametric predictive strategy from autism spectrum disorders (ASD) to schizophrenic spectrum disorders (SSD). Whereas perceptual inference in ASD is rigidly shaped by incoming sensory information, the SSD population is prone to overestimate the precision of their priors' models. Growing evidence considers brain oscillations pivotal biomarkers to understand how top-down predictions integrate bottom-up input. Starting from the conceptualization of ASD and SSD as oscillopathies, we introduce an integrated perspective that ascribes the maladjustments of the predictive mechanism to dysregulation of neural synchronization. According to this proposal, disturbances in the oscillatory profile do not allow the appropriate trade-off between descending predictive signal, overweighted in SSD, and ascending prediction errors, overweighted in ASD. These opposing imbalances both result in an ill-adapted reaction to external challenges. This approach offers a neuro-computational model capable of linking predictive coding theories with electrophysiological findings, aiming to increase knowledge on the neuronal foundations of the two spectra features and stimulate hypothesis-driven rehabilitation/research perspectives.

Region-specific elevations of glutamate + glutamine correlate with the sensory symptoms of autism spectrum disorders

Individuals on the autism spectrum are often reported as being hyper- and/or hyporeactive to sensory input. These sensory symptoms were one of the key observations that led to the development of the altered excitation-inhibition (E-I) model of autism, which posits that an increase ratio of excitatory to inhibitory signaling may explain certain phenotypical expressions of autism spectrum disorders (ASD). While there has been strong support for the altered E-I model of autism, much of the evidence has come from animal models. With regard to in-vivo human studies, evidence for altered E-I balance in ASD come from studies adopting magnetic resonance spectroscopy (MRS). Spectral-edited MRS can be used to provide measures of the levels of GABA + (GABA + macromolecules) and Glx (glutamate + glutamine) in specific brain regions as proxy markers of inhibition and excitation respectively. In the current study, we found region-specific elevations of Glx in the primary sensorimotor cortex (SM1) in ASD. There were no group differences of GABA+ in either the SM1 or thalamus. Higher levels of Glx were associated with more parent reported difficulties of sensory hyper- and hyporeactivity, as well as reduced feed-forward inhibition during tactile perception in children with ASD. Critically, the finding of elevated Glx provides strong empirical support for increased excitation in ASD. Our results also provide a clear link between Glx and the sensory symptoms of ASD at both behavioral and perceptual levels.

Somatosensory Temporal Discrimination in Autism Spectrum Disorder

Sensory differences are common in Autism Spectrum Disorder (ASD). While there is no well-accepted method to measure sensory differences objectively, there is accumulating evidence from recent years concerning sensory perception, including data concerning temporal discrimination thresholds of individuals with ASD as measured by different measures. The somatosensory temporal discrimination (STD) test measures the threshold at which an individual can temporally discriminate multiple tactile stimuli delivered in succession. We aimed to investigate tactile perception in ASD and hypothesized that children with ASD have impaired STD related to their subjective sensory symptoms and daily difficulties. Thirty adolescents with ASD and 30 typically developed subjects were recruited. The Childhood Autism Rating Scale, Strengths and Difficulties Questionnaire, and Adolescent/Adult Sensory Profile were implemented before STD evaluation. Average somatosensory detection (1.48 ± 0.42) and discrimination thresholds (112.70 ± 43.45) of the children with ASD were significantly higher (P = 0.010, P = 0.001, respectively) than those of the controls (1.18 ± 0.42, 79.95 ± 31.60, respectively). Sensory seeking scores of the ASD group (40.8 ± 7.60) were significantly lower (P = 0.024) than those of the control group (45.83 ± 9.17). However, the psychophsycal thresholds did not have any statistically significant relationships with subjective sensory symptoms or daily difficulties. This study demonstrates impaired sensory processing in ASD evaluated by STD and its lack of relationship with subjective sensory symptoms and daily difficulties. This psychophysical evidence of increased STD thresholds and decreased sensory seeking profile supports the disturbances in the regulation of sensory processing in ASD. LAY SUMMARY: Sensory differences are common in autism; however, there is no well-accepted method to measure them objectively. This study aims to investigate somatosensory differences and their relation with sensory and emotional/behavioral difficulties of children with autism. We show that autistic children have higher tactile discrimination thresholds and fewer sensory seeking behaviors. This supports the presence of impairments in sensory processing in autism. Measuring the sensory differences may help understanding clinical symptoms and neurobiological underpinings of autism. Autism Res 2021, 14: 656-667. © 2021 International Society for Autism Research and Wiley Periodicals LLC.