Induced suppression in spike responses to tone-on-noise stimuli in the auditory nerve of the pigeon.
Spike potentials were recorded from single, afferent fibres in the pigeon auditory nerve. Pure-tone stimuli were presented in quiet and in combination with wide band noise. Presented alone, tones produced tuned response areas; noise generally drove spike rate to well above the spontaneous rate measured in quiet. When presented in combination with noise, tones up to 75 dB SPL at frequencies far from the fibre's response area had no effect on the noise-driven spike rate. As the tone frequency was shifted towards the response area, from above or below CF, suppression of the noise-driven spike rate became stronger until the tone reached the edge of the response area. Suppression of the noise-driven rate was directly proportional to the level of the tone. Within the area of response to the tone, tone-driven spike rates generally were unchanged or variably decreased (occasionally slightly increased) by tone-on-noise stimulation, depending on the relation of the tone frequency to CF and the level of the tone relative to that of the noise. Tuning properties were unaffected. It is suggested that in the pigeon, the suppression of driven spike rate during presentation of combination stimuli, which is common to all fibres, depends on the same mechanism as the suppression of spontaneous firing by tones that is observed in a proportion of fibres (Temchin, A.N. (1988), J. Comp. Physiol. A 163, 99-115; Hill et al., (1989) Hear. Res. 39, 37-48).
Hill
K G
KG
Developmental Neurobiology Group, Research School of Biological Sciences, Australian National University, Canberra.
Mo
J
J
Stange
G
G
D000161:Acoustic Stimulation; D000200:Action Potentials; D000818:Animals; D010856:Columbidae / Q000502:physiology*; D009433:Neural Inhibition; D009475:Neurons, Afferent / Q000502:physiology*; D009622:Noise; D000159:Vestibulocochlear Nerve / Q000502:physiology*