Convergent validity of cortical auditory evoked potential indices of central auditory nervous system inhibition in people with and without tinnitus

Tinnitus is the perception of a ringing, buzzing, or other sound without the presence of an external stimulus. Reduced central auditory nervous system inhibition is a commonly reported mechanism contributing to a person's tinnitus perception. Different cortical auditory evoked potential (CAEP) studies have supported the presence of reduced inhibition in people with tinnitus. Although previous CAEPs used to study tinnitus do broadly represent inhibitory function, it is not entirely clear if the different CAEPs present similarly within an individual. To address this gap in knowledge, the current study evaluated the convergent validity between different CAEPs that broadly reflect inhibitory function, called sensory gating and onset-offset CAEPs. Convergent validity between sensory gating and onset-offset CAEPs was evaluated as a function of participant tinnitus status, stimulus frequency, and CAEP quantification approach. The results indicated that sensory gating and onset-offset CAEP responses indicative of inhibitory function did not demonstrate strong convergent validity. Further, the strength of convergent validity did not differ between people with and without tinnitus. However, experimental factors that yielded more robust CAEPs, such as broadband stimuli, and more comprehensive measures of amplitude, such as total response area, resulted in better convergent validity compared to higher frequency stimuli and more isolated measures of amplitude like peak amplitude. Overall, these findings suggest that the specific inhibitory mechanisms represented by sensory gating and onset-offset CAEPs differ. Therefore, each CAEP may be better suited to study distinct populations and/or inhibitory functions.