Auditory brainstem responses of the cat: on- and off-responses

The auditory brainstem on- and off-responses evoked by tone and noise bursts have been studied in the cat. The number and amplitude of the off-response waves are proportional to the frequency specificity of the on-response, being greatest for the 4-kHz tone burst and smallest for the noise burst. The threshold of the 0.5-kHz off-response is lower than that of the on-response, but the amplitude of the former does not increase at higher stimulus levels. Derived-band studies show that at 4 kHz the on-and off-responses have identical frequency content, the 0.5-kHz off-response is restricted to the 2- to 8-kHz frequency band, while the noise burst off-response is entirely high frequency. The off-response is an on-response and is evoked by acoustic transients from the loudspeaker transducer.