Coding of information in single auditory-nerve fibers of the goldfish.

Patterns of activity in single fibers of the saccular branch of the auditory nerve of goldfish were analyzed in response to acoustic stimulation. Neurons were categorized on the basis of differences in spontaneous activity patterns, rates of adaptation, and frequency response areas. The sensitivity and responsiveness of neurons are presented both in terms of impulse rate and synchronization (phase locking). Nonspontaneous neurons fall into two clear frequency response area categories based upon impulse rate criteria. Spontaneously active neurons have continuously distributed frequency response characteristics based upon synchronization criteria. Functions relating impulse rate responsiveness to frequency indicate that frequency is coded only crudely as an across-fiber pattern of impulse rates. Synchronization responsiveness functions show that frequency is coded temporally with the same precision in the goldfish auditory nerve that it is in mammals, at 1000 Hz and below.