Physiological response properties of cells labeled intracellularly with horseradish peroxidase in cat ventral cochlear nucleus

Abstract

To determine the correspondence between anatomical and physiological cell types in the ventral cochlear nucleus of the cat, intracellular injections of horseradish peroxidase were made into cells whose extracellular and intracellular responses to sound had been studied. Three identified cells responded to a short tone burst at their characteristic frequencies with an onset pattern. This pattern is characterized by a strong response to the onset of the stimulus. One was an octopus cell. The second cell, located in the octopus-cell area, was a giant cell with a few somatic spines and thin tapering dendrites; the intracellular record revealed that even in the absence of sound it received continuous synaptic input, while tones at characteristic frequency produced a sustained depolarization. A third cell, which had an onset response at low intensities and a chopper response at high intensities, was a stellate cell located in the intermediate acoustic stria with dendrites oriented parallel to the fiber tract. This cell had an unusually broad dynamic range in response to changes in intensity. Two cells with transient chopper response patterns were stellate cells in the posteroventral cochlear nucleus with many branched and beaded dendrites. Three cells with more sustained chopper response patterns were stellate cells in the anteroventral cochlear nucleus with fewer, less-branched, smooth dendrites. Two cells with primarylike responses to tones were bushy cells with numerous short, thin, highly branched dendrites in the posterior division of the anteroventral cochlear nucleus. Intracellular responses to tones at the characteristic frequency consisted of large brief depolarizations, which were not sustained. Another cell, which responded to tones in a phase-locked fashion, was also located in the anteroventral cochlear nucleus. It was a small, stellate cell with relatively few, smooth dendrites. The labeled cells largely support previous attempts at physiological-morphological correlations: (1) bushy cells exhibit primarylike pattern; (2) stellate cells exhibit chopper patterns; and (3) octopus cells exhibit an onset pattern. It was also demonstrated that more than one cell type can exhibit a particular response pattern.

Loudness Perception in the Domestic Cat: Reaction Time Estimates of Equal Loudness Contours and Recruitment Effects

“…9A). T-stellate neurons, the anatomical counterpart of the chopper response class, provide a major ascending projection to the contralateral inferior colliculus (Rhode et al 1983) and therefore may contribute to the abnormal AEPs that are recorded in humans who experience loudness recruitment.…”

Identification of cell types in brain slices of the inferior colliculus

“…5,8,10,24,27,28,60,61 In some cells, these membrane properties are correlated with the ability to follow trains of synaptic stimuli. 5,28 In vivo, the bushy cell exhibits phase locking to low-frequency acoustic stimuli 8,49 and plays a key role in pathways devoted to processing interaural temporal differences (ITD) where phase locking is an important requirement. 56 In contrast, sustained ®ring to current in vitro is seen in stellate neurons in the cochlear nucleus 61 as is a regular response to acoustic stimuli in vivo.…”

“…56 In contrast, sustained ®ring to current in vitro is seen in stellate neurons in the cochlear nucleus 61 as is a regular response to acoustic stimuli in vivo. 4,8,49,62 Such responses may disrupt the faithful transmission of temporal information, 28 particularly above 1 kHz where their phase locking is diminished. 48 Moreover, stellate cells bypass the ITD centers of the superior olive and project directly to the IC.…”

“…In the cochlear nucleus, discharge patterns correlate well with speci®c morphological cell types. 35,49,50 Efforts to characterize the intrinsic electrical properties of IC neurons are, however, just beginning 21,58,59 and discharge patterns have not been correlated with morphology. A more detailed analysis is needed to test the hypothesis that cell types are indicated by discharge pattern, and whether functionally de®ned cell types are correlated with other morphological properties such as Nissl pattern, cell body size or shape, dendritic branching, dendritic spines, or synaptic distribution.…”

Response patterns to sound associated with labeled globular/bushy cells in cat

“…Subsequently, PSTH response patterns have been greatly elaborated (Bourk, 1978;Blackburn and Sachs, 1989), and the relation of these PSTH patterns to the underlying morphology has been a subject of study. The introduction of intracellular labeling of physiologically characterized cells provided a firm basis for correlating physiological and morphological cell types (e.g., Rhode et al, 1983;Rouiller and Ryugo, 1984). Intracellular studies in brain-slices resulted in the biophysical characterization of several types of ion channels for many CN cell types, which also aided in the search for physiologicalmorphological correlations (e.g., Oertel, 1983;Manis and Marx, 1991;Rothman and Manis, 2003a;Cao et al, 2007).…”