Multisensory Interactions Between Somatosensory Stimulation and Vision in Autism Spectrum Disorders: An Electrophysiological Study

Background: Simultaneously presented multisensory stimuli are automatically integrated by typically developing individuals (TD) and frequently lead to enhancements in the ability to make behavioral discriminations in relation to unisensory inputs.  For example, simply looking at the body part where somatosensory stimulation is taking place appears to improve somatosensory discrimination (e.g., Taylor-Clarke & Haggard, 2002).  This may result from the coordination of visual and somatosensory spatial maps, and indeed the multimodal nature of spatial attention would argue for just this outcome.  Corresponding electrophysiological measures reveal that the somatosensory response is increased in amplitude when the stimulated location is observed compared to when it is not, suggesting that a magnification or better titrated tuning of the cortical response contributes to improved behavioral performance.   In Autism Spectrum Diagnoses (ASD) there is a hypothesized reduction in the integration of information across cortical areas and evidence for impaired multisensory processing. Since visual somatosensory integration requires long range connectivity, visual influences on somatosensory processing might be reduced in this population. 

Objectives: To examine the influence of vision on somatosensory processing in children with ASD, using a task with known behavioral and electrophysiological signatures.

Methods: A cohort of high functioning adolescents with ASD and IQ, gender, and handedness matched typically developing (TD ) adolescents will complete a forced choice intensity discrimination task to assay performance thresholds across four conditions: eyes closed (unisensory), view object (uninformative vision), view stimulated arm (informative vision), and view non-stimulated arm (vision directed at a different spatial location). Participants determine which of two stimulations presented simultaneously (in a staircase method) on the back of the left hand is more intense via a button press. Discrimination thresholds are acquired concurrently with ERPs.

Results: Preliminary analysis reveal significant interactions in behavioral discrimination thresholds between the informative vision and eyes closed conditions for the TD group, with better performance in the multisensory condition. We expect a different pattern of results for the adolescents with ASD with a) discrimination thresholds expected to be better for the ASD versus the TD group (e. g., Cascio et al., 2007; Tommerdahl et al., 2007) and b) less benefit in ASD from viewing the area where somatosensory stimulation is applied.

Conclusions: Individuals with ASD show enhanced discrimination abilities in relation to typically developing individuals across several modalities that includes touch (O'Riordan & Passetti, 2006; Tommerdahl, 2007) as well as instances of atypical multisensory integration (e.g. Bebko, et al., 2006; Russo et al., in prep; Smith & Bennetto, 2007). Together these findings suggest that behavioral and electrophysiological modulations of vision on somatosensation may differ in ASD. The findings from the present study will be discussed with respect to theories of multisensory integration and enhanced discrimination abilities, and will provide both behavioral and electrophysiological evidence regarding the integrity of multisensory systems and spatial tuning in children with ASD.