Investigation of cochlear mechanisms using combined acoustical and electrical stimulations

Electrically-evoked VIIIth nerve CAP responses evoked by electrical stimulation and derived by masking with sounds are recorded in the guinea pig, using different masking paradigms (pure tones and high-pass filtered white noise). CAP frequency threshold curves correlate with threshold curves determined by other means, in normal as well as in pathological guinea pigs. Amplitudes of the responses as a function of pure tones frequency and intensity are also measured. Such measurements provide an estimate of the number of fibers activated by the pure tones. These responses can be further analysed using masking with high-pass filtered white noise.