title: Effects of click polarity on brainstem auditory-evoked potentials in cochlear hearing loss: a working hypothesis.
abstract: The rarefaction-condensation differential potential (RCDP) obtained by subtracting brainstem auditory-evoked potentials (BAEPs) to C clicks from those to R clicks has been studied in 32 normal subjects and 31 cases of cochlear hearing loss. In normal subjects, no RCDP was recorded along the lower 30-55 dB of the JV latency-intensity function, thus defining the pre-RCDP range. The pre-RCDP range was always abolished in losses unmasking BAEPs from lower ( < 1 kHz) tonotopic regions. When the BAEP originated from higher ( > 1 kHz) tonotopic regions, the pre-RCDP range was either reduced or abolished. These results led to a working hypothesis based on single-unit data and stating a dual dependence of polarity effects on variables distributed along the tonotopic and intensity dimensions, with respective break-points at 1 kHz, and at the junction of the tip and tail of unit frequency tuning curves. The 1 kHz break-point could represent the upper frequency limit for phase locking in man.
mesh_terms: D000293:Adolescent; D000328:Adult; D001301:Audiometry, Pure-Tone; D001309:Auditory Threshold; D002648:Child; D003051:Cochlea / Q000503:physiopathology*; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D006311:Hearing Disorders / Q000175:diagnosis* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D012720:Severity of Illness Index