NEURAL PROCESSES IN THE DORSAL COCHLEAR NUCLEUS OF THE ANESTHETIZED CAT INVESTIGATED FROM UNIT RESPONSES TO ELECTRICAL-STIMULATION OF THE AUDITORY-NERVE

Extracellular responses of dorsal cochlear nucleus single units were r ecorded in response to biphasic, bipolar electrical stimulation of spi ral ganglion cells and their peripheral processes using a banded elect rode array in the scala tympani of the barbiturate anaesthetised cat. The DCN responses to this stimulus were the result of excitatory and s uppressive (including inhibitory) processes. The excitatory responses from DCN units were usually within a range of 1.8-2.8 ms and these res ponses were probably the result of monosynaptic input from the auditor y nerve. Latencies > 2.8 ms were most likely due to activation of di- and poly-synaptic pathways from auditory nerve fibres, except that lat encies between 3.5-4.75 in hearing animals could have arisen from elec trophonic mechanisms. Suppression of spontaneous activity was usually long acting, lasting > 70 ms following each pulse of the pulse train, but short acting suppression with a latency of 3.5-4.75 ms and a durat ion of < 10 ms was occasionally observed. These suppressive responses probably resulted from synaptic inhibitory input, but neural membrane properties may have contributed. In hearing animals, excitatory latenc ies within the range 1.8-5.2 ms were similar for units with different response area types or different PSTH patterns in response to acoustic CF tones or noise.