A new study out of UCLA's Semel Institute demonstrates that children diagnosed with autism spectrum disorder (ASD) have difficulty processing multiple sensory stimuli. The research was presented Thursday at the 13th Annual International Meeting for Autism Research (IMFAR) in Atlanta. The event presents research of The International Society for Autism Research (INSAR).
The researchers, led by Dr. Ted Hutman, studied the brain activity of adolescents diagnosed with ASD, as well as typically developing adolescents, when presented with mildly unpleasant sensations, such as loud traffic sounds or a rough wool cloth. Remarkably, when the stimuli were presented in isolation, brain activity was uniform across participants. These results were surprising because over-reaction to aversive stimuli is typically a hallmark of ASD.
However, stark differences were noted when both stimuli were presented simultaneously. Over-reactivity was displayed in two regions of the brain in ASD participants, the amygdala and sensory cortex, which are responsible for the understanding and evaluation of sensations, namely distinguishing whether that stimuli is a perceived threat. This indicates that the primary reaction isn't the issue, but rather that the deficit lies at the level of interpretation and processing of the sensation. This implies that children with ASD may have difficulty coping with certain sensory stimuli or a combination of stimuli.
Each set of sensations were presented four times. Brain scans of the amygdala indicated that non-ASD participants displayed habituation to the stimuli on each successive trial. That is, activity in that region of the brain decreased. Conversely, children with ASD either did not adjust to the stimuli or took longer to adapt. The results of the brain scans also correlated to parent reports of such reactions to sensory stimuli.
The results of this study are relevant to certain treatments and approaches to caring for those diagnosed on the autism spectrum, as well as anxiety disorders. When introducing an individual to a new environment, change in routine, novel sensory stimuli or new people, it's advisable to introduce only one novel stimulus at a time. In other words, ensure that the individual is comfortable on some level before bringing in a change to their environment.
The scientists also pointed out that this may be an indicator of individuals who are prone to anxiety, but not necessarily ASD. Further research into sensory issues associated with autism spectrum disorders is needed, especially given the updated diagnostic criteria in the DSM-V, which includes sensory deficits.