Latency of brain stem responses to chirps (linear frequency-ramp bursts). Relationship between certain physical parameters of the stimulus and nervous activity.
The latency of Jewett wave V to 4-kHz tone (T) bursts was first studied on 55 normally hearing ears. In another group of 31 subjects, shift in latency was investigated as a function of certain physical parameters of the stimulus. Using T bursts and chirps--frequency-ramp (FR) bursts of 6 ms duration with an interstimulus interval of 33 ms and a constant attenuation, we noticed that (1) in all subjects, wave V latency was greater with ascending FR bursts than with descending ones; (2) in all subjects with even slight sensorineural hearing losses, the difference in latency between 1-kHz T bursts and 1- to 2-kHz FR bursts was less than that between 2-kHz T bursts and 2- to 4-kHz FR bursts, and (3) in subjects with normal internal ears on standard audiometry, the converse occurred, except in 4 subjects in a group of 6 who had been exposed to loud impact noises. Possible underlying mechanisms are discussed.
D000161:Acoustic Stimulation; D000293:Adolescent; D000328:Adult; D001299:Audiometry; D001309:Auditory Threshold; D001933:Brain Stem / Q000502:physiology*; D002648:Child; D005071:Evoked Potentials; D005260:Female; D006311:Hearing Disorders / Q000175:diagnosis / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged