Auditory Brain Stem and Cochlear Responses in the Guinea Pig

Abstract

Two kinds of auditory responses in the guinea pig were simultaneously recorded to study their relations, i.e., the auditory brain stem response (BSR) and the cochlear responses (CM and AP) to click stimuli. The components of BSR, CM, and AP were compared as to their latencies and input-output relations as a function of stimulus intensity. The initial deflection of BSR was identified as CM from their close correlation. The basal turn of the cochlea most likely contributes to CM of BSR. This wave was followed by four distinctive neural components labeled P₁, P₂, P₃ and P₄ within 5 msec after stimulation The peak latencies of P₁ and P₂ did not coincide with those of N₁ and N₂ components of AP. The start of N₁, however, coincided with that of P₁ When the stimulus increased in strength, latencies of P₁ and P₂ were shortened in parallel to those of N₁ and N₂. As propagating along the auditory nerve, the components of AP would contribute respectively to P₁ and P₂. The peak latencies of P₃ and P₄ were 2.0 to 2.5 msec and 3.0 to 3.5 msec, respectively. These value were shorter than those in the cat.