Neural Validation of Sensory Subtypes in Autism Spectrum Disorder
Distinct sensory subtypes in ASD have been identified (Ausderau et al, 2014; Lane et al, 2014). Sensory subtypes have been posited as a means of identifying clinically meaningful subgroups within ASD. In one subtype model, two dimensions of sensory function have been proposed to underlie sensory subtypes – sensory reactivity and multisensory integration (MSI; Lane et al, 2014). This model is based on parent-report of sensory symptoms. Further elucidation and validation of dimensions underlying sensory subtypes in ASD is needed using neural and behavioural measures. In doing so, hypotheses relating to the mechanisms of sensory disturbance in ASD will be further refined and a new framework for the application of customised therapies will be developed.
In this paper, findings from preliminary studies will be discussed to address the question: do children with ASD classified using Lane et al’s sensory subtype model differ in their neural response profiles to sensory paradigms assessing sensory reactivity and multisensory integration?
Findings from four preliminary studies investigating the neural correlates of Lane et al’s sensory subtype model will be summarised. The studies include the following: 2 x event-related potential studies assessing brain activation response to an auditory oddball paradigm (total ASD n=60), 1 x event-related potential study assessing steady state EEG response to an auditory-tactile multisensory integration paradigm (ASD n=10), and 1 x cardiac study assessing heart rate variability in response to a novel sensory challenge protocol (n=42). All studies included children with ASD aged between 3-15 years. ASD participants were classified initially using Lane et al’s sensory subtype model based on parent ratings of sensory function on the Short Sensory Profile (McIntosh et al, 1999). This model classifies children into one of four sensory subtypes: Reactive High/MSI Low, Reactive High/MSI High, Reactive Low/MSI High, Reactive Low/MSI Low. Analyses were then conducted to examine differences between groups on each of the neural measures and for each of the sensory paradigms.
Preliminary findings indicate that brain activation potentials of children with ASD classified as Reactive High display a sustained positive shift in later (post-400ms) processing of novel auditory stimuli. Children with ASD classified as Reactive Low display no differences in brain activation potentials in the later processing of novel and standard auditory stimuli. Further, children with ASD classified as Reactive High, show increased cardiac sympathetic activity (as measured by pre-ejection period) throughout a novel sensory challenge protocol. Data from the event-related potential study examining response to a MSI protocol is currently being collected.
On balance, the findings of these preliminary studies provide support for the hypothesis that neural profiles in response to sensory protocols assessing sensory reactivity vary on the basis of sensory subtype classification. Further study is required to confirm these differences particularly in response to sensory protocols assessing MSI. Neural validation of the sensory subtype model in ASD provides an important link between the ‘bench and the ball pit’ by establishing a framework for both mechanism discovery and clinical practice.