Marginal shell of the anteroventral cochlear nucleus: Single-unit response
properties in the unanesthetized decerebrate cat.
S. Ghoshal and D. O. Kim.
Division Otolaryngology, Surgical Research Center, Department of Surgery,
Neuroscience Program, Biomedical Engineering Program, University of
Connecticut Health Center, Farmington, CT 06030-1110, USA.
APStracts 4:0014N, 1997.
ABSTRACT
The marginal shell of the anteroventral cochlear nucleus (AVCN) is
anatomically different from its central core. We investigated 38 single units
in the shell of 10 cats and contrasted them with 62 single units in the core
of 15 cats. The sites of all shell units were localized using reconstructed
electrode tracks. The shell units were divided into acoustically well-driven
(68%) and weakly/not-driven (32%) subgroups. The shell units mostly exhibited
low spontaneous rates (SR). Among the well-driven shell units, a large
majority (68%) exhibited wide dynamic ranges (ò 50 dB) to tones, noise or
both, with some as wide as 89 dB. In contrast, a large majority (80%) of the
core units exhibited narrow dynamic ranges (< 50 dB) to tones and noise. The
post-stim ulus time histograms (PSTHs) of the well-driven shell units included
pause-build (29%), onset (24%) and unusual (33%) types while those of the core
units were mainly primarylike (47%) and chopper (29%) types. The excitatory-
inhibitory areas (EIAs) of the well-driven shell units included types I/III
(47%), III (22%), IV (13%) and II (9%) while those of the core units were
mainly types III (52%) and I/III (32%). Based on Fisher's exact tests, we
conclude that the shell and core neural groups of the AVCN are significantly
different regarding all of the following physiological characteristics: SR,
maximum driven rate, threshold and dynamic range to tones and noise, frequency
response area, PSTH type, latency, and EIA types. Wide dynamic ranges of the
well-driven shell units suggest that they may play a role in encoding absolute
intensity of acoustic stimulus.
Received 19 June 1996; accepted in final form 13 December 1996.
APS Manuscript Number J487-6.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 21 January 1997