Responses of dorsal cochlear nucleus units to noise and electrical stimulation of the auditory nerve [Abstract]

Abstract

The synaptic organisation and physiology of the dorsal cochlear nucleus (DCN) have been investigated by electrical stimulation of the auditory nerve (1). Whether electrical and acoustic stimulation activate the same pathways to the DCN is not clear (2). To examine this question we have explored the extracellular response of DCN units to both acoustic and electrical stimuli in the barbiturate anaesthetised cat. The electrical stimulus was a train of biphasic current pulses and 2mA, 100-200 μsec/phase and presented at 200 pulses per second via a bipolar electrode inserted into the scala tympani. The acoustic stimulus was pseudorandom noise. These stimuli have been observed to cause auditory nerve activation throughout the length of the cochlea and were the same duration, 100 ms. The larger number of units, group I, had action potentials with latencies of < 2.9 ms in response to an electrical stimulus and a similar discharge rate of both the electrical stimulus and noise. Group II had latencies of > 2.9 ms, a high discharge rate to noise and a low discharge rate to the electrical stimulus. These discharge rate phenomena could have arisen from both stimuli activating the same pathways and the temporal interaction of excitatory and inhibitory drives received by the DCN unit.