Rhythmic discharge properties of caudal cochlear nucleus neurons during postnatal development in cats

Edward J. Walsh, Jo Ann McGee

Research output: Contribution to journalArticle

28 Scopus citations

Abstract

Action potentials recorded extracellularly from neurons within the caudal cochlear nuclei of developing cats exhibited distinctive temporal characteristics (i.e., rhythmic responses) in response to long-duration acoustic stimuli including both tone and noise bursts. Unlike the homogeneous response characteristics of auditory nerve fibers, cochlear nucleus neurons exhibited many variations in rhythmic discharge patterns. The majority of neurons within the caudal CN of kittens younger than 10 days of age responded rhythmically to long-duration acoustic stimuli, however, the percentage of neurons responding rhythmically steadily decreased thereafter, and by the end of the second postnatal week most tonically-responding neurons maintained sustained steady-state discharge rates throughout stimulation. Discharges of neurons recorded during the transitional ages (around 13 days) were rhythmic at low sensation levels and exhibited adultlike sustained patterns at higher levels. Using constant sensation level stimuli (re individual neuron thresholds), burst frequencies remained essentially constant during the period of development in which rhythmic responses were observed. Intervals separating discharge bursts decreased as stimulus intensities increased for all neurons studied during therelevant period, but were not related in an orderly way to stimulus frequency. The effects of intensity on response periodicity were not mimicked by altering the amount of neurotransmitter present at the postsynaptic cell through microionophoresis of excitatory amino acids and their antagonists onto the surface of neurons within the caudal CN. In addition, some immature neurons which responded phasically to acoustic stimuli responded rhythmically during the simultaneous presentation of acoustic stimuli and neuroexcitatory agents (i.e., glutamate). These results suggest that the source of the rhythmicity is not intrinsic to neurons in the caudal CN. Based on these and other observations we conclude that the most probable source of response periodicity observed early in development is the domination of inner hair cell output by efferent projections of the olivocochlear bundle, the temporal discharge patterns of which are also periodic.

Original languageEnglish (US)
Pages (from-to)233-247
Number of pages15
JournalHearing Research
Volume36
Issue number2-3
DOIs
StatePublished - Nov 1988

Keywords

  • Amino-phosphonovalerate
  • Auditory
  • Cochlear nucleus
  • Development
  • Glutamate/aspartate
  • Microiontophoresis

ASJC Scopus subject areas

  • Sensory Systems

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