Neurons in the cochlear nucleus investigated with tone and noise stimuli.

1. Responses of cochlear nucleus neurons to stationary and amplitude modulated noise stimulation are investigated and compared with responses to tonal stimuli. 2. Cross-correlation functions, computed from responses to stationary noise stimulation, showing a clear oscillation could be most easily obtained from low CF fibres presumed to be auditory nerve fibres and low CF cochlear nucleus neurons showing only activation response and a primarylike temporal pattern of response to tone bursts. This reflects good quality of phase locking in these neurons. 3. The CCF reflects strongly the frequency selectivity of the neuron as revealed in its response area but not the temporal pattern of response to tone bursts. 4. Responses to noise bursts are correlated with the responses to tone bursts of many different frequencies in both their sign (i.e. activation or suppression) and their temporal pattern. 5. The concept of two independently operating mechanisms, one depending on the fine time structure of the stimulus (the carrier) and the other on its amplitude, and determining respectively the fine time structure of the response pattern and its magnitude, is introduced. Experimental data are presented which lend support to the adequacy of the description in the majority of cases and reveal its shortcomings in others.