Quantitative assessments of neuroadaptation in autism

Background:

Adults with autism exhibit inhibitory deficits that are often manifested in behavioral excesses, 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

Objectives:

This study exemplifies newly developed methods 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) efficient and sensitive measures of change following treatment.

Methods:

The sensory discriminative capacity of 10 subjects with autism and 10 controls was compared both before and after short duration conditioning stimuli and in the presence/absence of synchronizing stimuli. Specifically, vibrotactile amplitude discriminative capacity was obtained both in the presence and absence of 1 sec conditioning stimuli that were delivered 1 sec prior to the comparison stimuli. Additionally, temporal order judgment was obtained in the presence and absence of synchronizing tactile stimuli.

Results:

Although conditioning stimuli had a pronounced effect on the amplitude discriminative capacity of the control subjects, the conditioning stimuli had little or no impact on the sensory discriminative capacity of the subjects with autism. Similarly, while synchronizing stimuli had a significant effect on sensory perception in the control subjects, it had little impact on the sensory percepts of individuals with autism.

Conclusions:

The lack of impact of the conditioning 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 in autism and perhaps monitor the efficacy of pharmacological or behavioral treatments.