Intracellular study of synaptic events related to phase-locking responses of cat cochlear nucleus cells to low frequency tones.

In this study intracellular recording techniques were used to study the synaptic events related to phase-locking of cochlear nucleus cells to low frequency stimuli. A variable degree of phase-locking was noted even with units of the same low characteristic frequency. With low frequency phase-locking units an excitatory postsynaptic potential (EPSP) occurred in response to each period of the frequency stimulus, but the probability of an action potential occurring decreased as the frequency of the stimulus was raised. Complex units were described which phase-locked at lower frequencies of stimulation but did not at higher frequencies where the temporal pattern of firing to tone burst stimulation changed as well. Results are discussed as they relate to the frequency following response recorded with gross electrodes in the lower auditory pathway and the relationship to frequency coding in the auditory pathway.