The effects of congenital deafness on auditory nerve synapses and globular bushy cells in cats

Elizabeth E. Redd, Tan Pongstaporn, David K. Ryugo

Research output: Contribution to journalArticle

Abstract

It is well known that auditory deprivation affects the structure and function of the central nervous system. Congenital deafness represents one form of deprivation, and in the adult white cat, it has been shown to have a clear effect upon the synaptic interface between endbulbs of Held and spherical bushy cells. It is not known, however, whether all primary synapses are affected and/or whether they are affected in the same way and to the same extent. Thus, we studied a second neuronal circuit in the deaf white cat involving modified (small) endbulbs and globular bushy cells. Compared to normal hearing cats, modified endbulbs of congenitally deaf cats were 52.2% smaller but unchanged in structural complexity. There was also a striking loss of extracellular space between ending and cell body. The somata of postsynaptic globular bushy cells were 13.4% smaller and had enlarged postsynaptic densities. These data reveal that axosomatic synapses demonstrate abnormal structure as a consequence of deafness and that the extent of the abnormalities can vary with respect to the circuits involved. The implication of these observations is that synaptic anomalies would introduce differential delays within separate circuits, thereby desynchronizing neural activity from sound stimuli. This loss of synchronization could in turn disrupt temporal processing and compromise a host of related functions, including language comprehension. (C) 2000 Elsevier Science B.V.

Original languageEnglish (US)
Pages (from-to)160-174
Number of pages15
JournalHearing Research
Volume147
Issue number1-2
DOIs
StatePublished - Sep 2000

Keywords

  • Endbulb
  • Extracellular cisterna
  • Hearing
  • Postsynaptic density

ASJC Scopus subject areas

  • Sensory Systems

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