Temporal response properties of primary-like units in the anteroventral cochlear nucleus to acoustic and electrical stimulation [Abstract]

Abstract

Auditory information is encoded in the central auditory pathway in both the spatial and temporal domains. The magnitude of the contributing role of each domain remains unresolved. Scala tympani electrical stimulation of the auditory pathway may provide insights into the relative importance of these different coding domains. This study investigates the temporal response of acoustically-characterised primary-like units in the anteroventral cochlear nucleus (AVCN) to acoustic and electrical stimulation. Response synchrony to acoustic stimulation at and below the units characteristic frequency (CF) and to electrical stimulation at rates up to 1000 Hz has been analysed with respect to the phase of the stimulus and the intervals between successive spikes. Normal hearing adult cats were anaesthetised with pentobarbitone sodium (Nembutal; 45 mg/k.g l.V.) and the AVCN exposed via a dorsal approach. Micropipette electrodes (4 -30 M?) were advanced dorsoventrally through the AVCN and the response timing of isolated units recorded on computer for off-line analysis. To compare the variance in the timing of the response with respect to the phase of the stimulus and with respect to the intervals between successive responses, cross correlation of spike timing and cross-correlation of spike intervals were performed. For acoustic stimulation these results show that the variance in the timing of the response with respect to the phase of the stimulus is lower (i.e. higher correlation) than that seen in the interval variance. A similar result was not however found following electrical stimulation. Cross-correlations on different order intervals, (i.e. 1st, 2nd, 3rd etc.), show that variance across the different order intervals does not systematically vary. These data suggest that the temporal response to acoustic stimuli at this level of the auditory pathway more precisely codes stimulus phase than stimulus interval.