Bilaterally Recorded Early Acoustic Responses

Abstract

Early acoustic responses (latencies from 1 to 8 ms) were recorded simultaneously from each mastoid to give records which were ipsilateral and contralateral to the stimulated ear. Six normally hearing subjects were tested at three stimulus levels; the ipsilateral and contralateral data were compared and their basic statistical properties evaluated. Many of these properties are common to both the ipsilateral and contralateral records. They differ mainly in that the ipsilateral record comprises the five peaks, N₁ to N₅, whereas the contralateral record comprises four peaks, N₂ to N₅; the ipsilateral response amplitudes are generally the greater and the contralateral latency variances are generally larger. These results are in agreement with data obtained from patients with pathological brainstem conditions.