Neural response patterns for frequency.changing signals

In previous studies, whole nerve AP's recorded from the guinea pig VIII nerve were shown to differ in response to 5‐ms rising and falling frequency tone glides (Shore and Cullen, 1978). The rising glide resulted in larger N1 and N2 amplitudes. The present study examined AP's in response to 2‐ms rising and falling glides with seven differing rates of frequency change. Waveform analysis indicates greater N1 and N2 amplitudes in response to the rising glides for rates of change up to 160 Hz/ms. At rates of change greater than 160 Hz/ms, amplitudes are larger for the falling glide. Later peaks show larger amplitudes for rising glides at all rates, suggesting convergence of neural input. These findings suggest that directional responses to frequency‐changing signals reported for higher‐order neurons are not solely a function of neuron type. Rather, differential coding is initiated at a cochlear level. [Work supported in part by NIH.]