The measurement of electrodermal activity (EDA) provides a window into sympathetic nervous system activation via detection of change in sweat gland activity. Using EDA measures, the innovative Sensory Challenge Protocol (SCP) enables researchers to study sympathetic reactivity to sensory stimuli in a controlled laboratory environment. The SCP is specifically designed for studies of children with developmental and behavioral conditions involving impaired sensory modulation (Miller et al., 1999; Miller et al., 2001). It is a painless and non-intrusive psychophysiological assessment in which a series of sensory stimuli are administered in a child-friendly laboratory.
The purpose was to provide empirical evidence regarding differences in reactivity to sensory stimulation of children with and without autism. This study uses the SCP, which includes 3 phases (baseline, “sensory challenge”, and recovery), to measure sympathetic reactivity via EDA data at rest and in response to stimuli. Six types of stimulation were included in the “sensory challenge”: auditory (tone and siren), visual (strobe light), tactile (feather), olfactory (wintergreen-scented oil), and vestibular (automated back-tilted chair) stimulations. Each stimulus lasts 3 seconds, and 8 trials were given for each type of sensory stimuli.
Twenty-two children diagnosed with autism (AD) and 18 typically-developing children (TD) ages 5-12 were recruited from neighborhood clinics and communities. No age differences between the 2 groups were found. The Social Communication Questionnaire was used to confirm the diagnosis of autism, and the Sensory Processing Measure Home Form (SPM) was used to measure children’s behavioral responses to sensory stimuli in natural environments, via parental report. Data from the TD group were included in the final analysis only if both of their sub-scores and total scores (in the SPM) were in the typical range.
Independent t-tests were used to evaluate differences between the AD and TD groups. For the parental reports on the SPM, the two groups are significantly different in all subscores and the total scores. For the EDA, at the two resting periods (baseline and recovery), the AD group demonstrated significantly higher levels of skin conductance (baseline: p=0.01; recovery: p=0.04). The AD group also showed significantly higher mean magnitude of the skin conductance orienting response (SCOR) to the visual (p<0.01), siren (p=0.03), olfactory (p=0.02), and vestibular (p<0.01) input than the TD group.
Results suggest that children with autism tend to have higher arousal levels and are more physiologically reactive to sensory input than the typically-developing children. Additional analysis of amplitude revealed that a small number of children in the TD and AD groups were non-responders in different sensory input. Moreover, a preliminary analysis indicates that children’s responses to different types of sensory inputs in the laboratory were correlated with the parental observation in the natural environment reported in the SPM Home Form. These issues will be further investigated in future studies.