Perceptual metrics of individuals with autism provide evidence for disinhibition

Adults with autism exhibit inhibitory deficits that are often manifested in behavioral modifications, such as repetitive behaviors, and/or sensory hyper-responsiveness. If such behaviors are the result of a generalized deficiency in inhibitory neurotransmission, then it stands to reason that deficits involving localized cortical-cortical interactions--such as in sensory discrimination tasks--could be detected and quantified. This study exemplifies a newly developed method for quantifying sensory testing metrics. Our novel sensory discrimination tests may provide (a) an effective means for biobehavioral assessment of deficits specific to autism and (b) an efficient and sensitive measure of change following treatment. The sensory discriminative capacity of ten subjects with autism and ten controls was compared both before and after short duration adapting stimuli. Specifically, vibrotactile amplitude discriminative capacity was obtained both in the presence and absence of 1 sec adapting stimuli that were delivered 1 sec prior to the comparison stimuli. Although adaptation had a pronounced effect on the amplitude discriminative capacity of the control subjects, little or no impact was observed on the sensory discriminative capacity of the subjects with autism. This lack of impact of the adapting stimuli on the responses of the subjects with autism was interpreted to be consistent with the reduced GABAergic-mediated inhibition described in previous reports. One significant aspect of this study is that the methods could prove to be a useful and efficient way to detect specific neural deficits and monitor the efficacy of pharmacological or behavioral treatments in autism.