Brainstem auditory evoked potentials (BAEPS) and selective attention revisited

Evidence of peripheral filtering of auditory information at the cochlear and brainstem levels was sought using brainstem auditory evoked potentials (BAEPs) recorded during auditory and visual tasks. It can be argued that the discrimination tasks used in the past to investigate peripheral filtering of sensory information in humans involve two levels of discrimination, the consequences of which result in two independent types of inhibition: crossmodal inhibition as a result of between-modality discrimination, and intramodal inhibition as a result of within-modality discrimination. Therefore, the observed effects on the BAEPs may reflect the extent to which these two types of inhibition are engaged. In this investigation a paradigm that included two non-discrimination (passive) tasks and two discrimination (active) tasks was employed. BAEPs recorded during listening (a passive auditory task) provided a baseline measure, against which comparisons of BAEPs recorded during auditory and visual discrimination could be made for independent evidence of crossmodal and intramodal inhibition. The data in this study did not support the presence of two types of inhibition proposed above, or show evidence of peripheral filtering of auditory information at the cochlear and brainstem levels. However, the sensitivity of BAEPs to efferent system activation at the cochlea and hence their value as a tool in investigations of peripheral filtering in humans was questioned.