Cochlear summating potential to broadband clicks detected from the human external auditory meatus. A study of...

The cochlear summating potential (SP) preceding the auditory nerve compound action potential (AP) was elicited by broadband alternating condensation and rarefaction clicks and recorded by noninvasive electrodes from the external auditory meatus (EAM) of 60 volunteers of both sexes, 12 to 67 years old, who had normal hearing for age. Quantitative data were obtained on: the number of ears displaying measurable SPs; the SP detection level; the SP onset, peak and rise times; the duration of the SP-AP complex; the SP amplitude; and the SP/AP amplitude ratio. Previously unknown relationships were unveiled between the amplitude, but not the temporal, measures of the SP and laterality, sex, age, and audiometrically determined hearing thresholds to 4 to 8 kHz tones. The highest correlations were obtained with these last thresholds, which suggested that receptors in the basal turn of the cochlea played a dominant role in the generation of the EAM-detected SP. To improve on existing techniques for determining abnormal SP elevation, a multiple regression method was devised that utilized sex, age, 4 to 8 kHz hearing thresholds, and AP voltage to establish upper normal limits of SP amplitude for individual subjects and ears.