Individual differences in autonomic activity affects brainstem auditory frequency-following response amplitude in humans.

Innervation of the cochlea by sympathetic fibers suggests that the autonomic nervous system (ANS) may influence auditory information processing. The brainstem frequency-following response (FFR) and spontaneous skin conductance activity (SCA) were measured while subjects discriminated between long (rare) and short (frequent) duration tones. When subjects were divided into three groups on the basis of SCA, those with low SCA variability had larger FFR amplitudes. These results agree with the only other study to report ANS effects on brainstem auditory evoked responses [28]. It is proposed that individual differences in autonomic response patterns may account for some of the amplitude variation reported in brainstem evoked potential studies.