Intracellularly Labeled Fusiform Cells in Dorsal Cochlear Nucleus
of the Gerbil. II. Comparison of Physiology and Anatomy
Kenneth E.
Hancock1 and
Herbert F.
Voigt1,2
1Department of Biomedical Engineering and
Hearing Research Center and 2Department of
Otolaryngology, Boston University, Boston, Massachusetts 02215-2407
The Journal of Neurophysiology Vol. 87 No. 5 May 2002, pp. 2520-2530.
Abstract
Hancock, Kenneth E. and
Herbert F. Voigt.
Intracellularly Labeled Fusiform Cells in Dorsal Cochlear Nucleus
of the Gerbil. II. Comparison of Physiology and Anatomy.
J. Neurophysiol. 87: 2520-2530, 2002.
Fusiform
cells represent the major class of dorsal cochlear nucleus (DCN)
projection neuron. Although much is understood abouttheir physiology
and anatomy, there remain unexplored issues withimportant functional
implications. These include interspeciesdifferences in DCN physiology
and the nature of the cell-to-cellvariations in fusiform cell
physiology. To address these issues,a quantitative examination was
made of the physiology and anatomyof 17 fusiform cells from a
companion study. The results suggestthat the basal dendrites
of gerbil fusiform cells may be electrotonicallymore compact than
those of the cat. This relative decrease inthe filtering of excitatory
inputs might account for the lowerincidence of type IV units in that
species. These data also suggestthat the gerbil DCN lacks the
high-frequency specialization describedin the cat, because the
tonotopic arrangement of the gerbil fusiformcells quantitatively
matches the place-frequency map for the gerbilcochlea. Certain
physiological properties have anatomical correlates.First, the basal
dendrites of low spontaneous rate cells are directedaway from the soma
only in the caudal direction, while the highspontaneous rate cells
have basal dendrites extending rostrallyand caudally. Second, input
resistance was dominated by the surfacearea of the apical dendrite.
Third, the discharge pattern wascorrelated with apical dendrite
orientation. Finally, there wasa spatial gradient of sensitivity to
broadband noise organizedat least partially within an isofrequency
axis. Such trends indicatethat neighboring fusiform cells are endowed
with different signalprocessingcapabilities.
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