Assessment of Stimulus Overselectivity with Tactile Compound Stimuli in Children with Autism

Autism spectrum disorder in the scope of tactile processing

Sensory processing abnormalities are among the most common behavioral phenotypes seen in autism spectrum disorder (ASD), typically characterized by either over- or under-responsiveness to stimulation. In this review, we focus on tactile processing dysfunction in ASD. We firstly review clinical studies wherein sensitivity to tactile stimuli has traditionally been assessed by self-, parent- and experimenter-reports. We also discuss recent investigations using psychophysical paradigms that gauge individual tactile thresholds. These more experimentally rigorous studies allow for more objective assessments of tactile abnormalities in ASD. However, little is understood about the neurobiological mechanisms underlying these abnormalities, or the link between tactile abnormalities and ASD symptoms. Neurobiological research that has been conducted has pointed toward dysfunction in the excitation/inhibition balance of the central nervous system of those with ASD. This review covers recent efforts that have investigated tactile dysfunction in ASD from clinical and behavioral perspectives, and some of the efforts to link these to neurobiology. On the whole, findings are inconsistent, which can be ascribed to the subjectivity of clinical assessments, the heterogeneity of ASD cohorts, and the diversity of tactile sensitivity measures. Future endeavors into understanding tactile processing differences in ASD will greatly benefit from controlled experiments driven by neurobiological hypotheses.

Examination of the prevalence of stimulus overselectivity in children with ASD

Many individuals with autism spectrum disorders (ASD) display stimulus overselectivity, wherein a subset of relevant components in a compound stimulus controls responding, which impairs discrimination learning. The original experimental research on stimulus overselectivity in ASD was conducted several decades ago; however, interventions for children with ASD now typically include programming to target conditional discriminations in ways that might minimize the prevalence of stimulus overselectivity. The present study assessed 42 children who had been diagnosed or educationally identified with ASD using a discrimination learning assessment. Of these 42 children, 19% displayed overselective responding, which is a lower percentage than that seen in early research. Possible explanations for this decreased percentage, implications for intervention, and future directions for research are discussed.

Stimulus overselectivity in typical development: implications for teaching children with autism

Stimulus overselectivity is widely accepted as a stimulus control abnormality in autism spectrum disorders and subsets of other populations. Previous research has demonstrated a link between both chronological and mental age and overselectivity in typical development. However, the age at which children are developmentally ready to respond to discriminations involving simultaneous multiple cues has not been established. Thirty-seven typically developing preschoolers completed a task requiring response to simultaneous cues (color and shape) to establish the age at which typically developing children can successfully respond to multiple cues. Results demonstrate that typically developing children under 36 months of age have difficulty responding to multiple cues. Implications for behavioral treatment for autism are discussed.

A retrospective review of the effectiveness of aripiprazole in the treatment of sensory abnormalities in autism

Although sensory deficits are frequently observed in autistic individuals, pharmacologic interventions targeting these abnormalities are lacking. The goal of this investigation was to assess the effectiveness of aripiprazole in targeting sensory deficits in children and adolescents with autism. Using an outpatient clinic registry for pervasive developmental disorder, 13 individuals who had received aripiprazole for treating disruptive behaviors and had completed behavioral rating scales (aberrant behavior checklist [ABC] and sensory profile questionnaire [SPQ]) were identified. Mean treatment duration was 24.4 weeks with a mean final aripiprazole dosage of 10.8 mg. Aripiprazole yielded improvements in the total ABC and in several items of the SPQ including registration, inattention/distractibility, auditory processing, and modulation of visual input affecting emotional responses and activity level, suggesting that aripiprazole might be beneficial in targeting sensory abnormalities in autism.

Stimulus overselectivity four decades later: a review of the literature and its implications for current research in autism spectrum disorder

This review of several topics related to "stimulus overselectivity" (Lovaas et al., J Abnormal Psychol 77:211-222, 1971) has three main purposes: (1) To outline the factors that may contribute to overselectivity; (2) to link the behavior-analytical notion of overselectivity to current nonbehavior-analytical research and theory; and (3) to suggest remedial strategies based on the behavior-analytical approach. While it is clear that overselectivity is not specific to autism spectrum disorder (ASD) and also that not all persons with ASD exhibit overselectivity, it is prevalent in ASD and has critical implications for symptoms, treatment, research, and theory. Weak Central Coherence and Enhanced Perceptual Functioning theories are briefly considered. The research areas addressed here include theory of mind, joint attention, language development, and executive function.

Over-selectivity as a learned response

An experiment investigated the effects of different levels of task complexity in pre-training on over-selectivity in a subsequent match-to-sample (MTS) task. Twenty human participants were divided into two groups; exposed either to a 3-element, or a 9-element, compound stimulus as a sample during MTS training. After the completion of training, both groups were tested on an MTS task using a novel 6-element compound sample stimulus. The level of over-selectivity at test was influenced by the training. Specifically, the group exposed to a more complex (9-element) training task displayed higher levels of over-selectivity at test than the group with a less complex training task. The results suggest that over-selectivity may be a learned response to complex situations, and are discussed with respect to theories and treatments for over-selectivity.