The normal summating potential recorded from external ear canal.
With a "plastic leaf" electrode, cochlear summating potential (SP) and auditory nerve action potential (AP) responses to rectangular-pulse clicks were recorded from the ear canal skin surface of 96 normal-hearing ears of 48 subjects. The main goals of this investigation were to develop a more precise characterization of the relationship between SP and AP amplitudes across normal ears and to determine the confidence limits of this relationship so that a more accurate "normal limit" could be established for clinical testing. The results suggest that the across-subjects SP-AP amplitude relationship is linear. Also, SP scatter increases as AP amplitude increases, but the scatter is equalized by log transforming the data. The distance of the SP from the log-transformed SP-AP estimating line in SE ("AP-normalized SP amplitude") was found to be superior to the SP/AP amplitude ratio as a method of adjusting SP to AP amplitude, because the SP/AP ratio varied significantly with AP amplitude both across subjects and with different ear canal electrode positions.
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D000200:Action Potentials; D000293:Adolescent; D000328:Adult; D000375:Aging; D003055:Cochlear Microphonic Potentials; D004424:Ear Canal; D004566:Electrodes; D005072:Evoked Potentials, Auditory; D005260:Female; D006801:Humans; D008297:Male; D008433:Mathematics; D012737:Sex Factors; D000159:Vestibulocochlear Nerve / Q000502:physiology