Initial discharge latency and threshold considerations for some neurons in cochlear nuclear complex of the cat.

1. Latency behavior of neurons in the cochlear nuclear complex was studied in 45 barbiturate-anesthetized cats. Stimuli were tonal bursts usually 50-500 ms in duration. 2. Latency of the initial discharge is a systematic function of the frequency and intensity of the tone for a large class of neurons which are termed latency precedence cells. Most cells in the anteroventral cochlear nucleus and many neurons in the anterior division of the posteroventral nucleus belong to this class. Unless otherwise stated, all findings pertain to this cell group. 3. There is usually a correspondence between the discharge rate of a given neuron and the latency of the initial discharge, the higher the discharge rate the shorter the latency. Hence, for any intensity level evoking less than saturation discharge rate, initial discharge latency tends to be ‘shortest for best-frequency stimuli and lengthens systematically as the stimulating frequency departs in either direction from best frequency. However, for some cells, intense stimuli above best frequency evoke initial discharges at latencies which are similar to those produced by best-frequency stimuli. 4. An unexpected finding was that the initial discharge at threshold is a low probability event that can be evoked, except for a short initial time period, by any stimulus cycle throughout the tone duration. Hence, tone duration is a parameter in determining the threshold. Within limits, the longer the