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Structural and functional properties distinguish two types of multipolar cells in the ventral cochlear nucleus
Author(s) -
Smith Philip H.,
Rhode William S.
Publication year - 1989
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.902820410
Subject(s) - biology , stimulus (psychology) , depolarization , neuroscience , cochlear nucleus , inhibitory postsynaptic potential , anatomy , population , sensory system , nucleus , biophysics , psychology , demography , sociology , psychotherapist
Abstract We distinguish two types of large multipolar cells designated sustained (C s ) and onset (O c ) choppers in the anterior posteroventral cochlear nucleus (A‐PVCN)/nerve root region on the basis of certain anatomical and physiological features. C s axons head into the trapezoid body, while O c axons use the intermediate acoustic stria of Held. At the electron microscopic (EM) level, collateral terminals of O c axons contain pleomorphic vesicles; C s terminals contain small round vesicles. C s dendritic trees tend to be distributed in a stellate fashion while O c dendritic trees tend to be elongated. At the EM level the sustained chopper somata are sparsely innervated while the proximal dendritic tree receives considerably more input. The O c somata are highly innervated and this heavy innervation continues out onto the proximal dendrites. Distally the dendritic innervation falls off considerably for both categories. Physiologically, members of the O c population have wider dynamic ranges at the characteristic frequency (CF), wider response areas that are typically not flanked by inhibitory sidebands, and responses to short tones that do not show the same form of regularity expressed by sustained choppers. Intracellularly the sustained choppers exhibit sustained depolarization to short tones for the duration of the stimulus with resultant regular spiking at a rate that is stimulus level dependent. The response to swept tone shows this same level‐dependent regularity. In response to tones, the O c cells also show a sustained depolarization whose amplitude is stimulus‐level dependent but whose range is much greater and whose onset is initiated more abruptly. Although the onset component of the O c spike output is reliably initiated by these levels of depolarization, regular firing to the sustained depolarization is not initiated at levels of depolarization that would surely generate regular firing in sustained choppers. This regularity is also absent in the swept tone response despite marked levels of excitation.