Electrically evoked single-fiber action potentials from cat: Responses to monopolar, monophasic stimulation

Charles A. Miller*, Paul J. Abbas, Barbara K. Robinson, Jay T. Rubinstein, Akihiro J. Matsuoka

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

106 Scopus citations

Abstract

We recorded action potentials from single auditory-nerve fibers of cats using monophasic current pulses delivered by a monopolar intracochlear electrode. These simple stimuli provided a means of investigating basic properties and hypotheses of electrical excitation. Standard micropipette recording techniques were used. Responses to anodic (positive) and cathodic (negative) stimulus pulses were recorded separately to evaluate stimulus polarity effects. Mean spike (action potential) latency was polarity dependent, with greater latencies for cathodic stimulation. Threshold stimulus level was also polarity dependent, with relatively lower cathodic thresholds. Both effects are consistent with trends reported in the compound action potential. Variability in single-fiber latency (i.e., jitter) was dependent upon stimulus polarity. In contrast, the slope of single-fiber input-output functions failed to show a clear polarity dependence, although such trends have been seen in the compound action potential data. We also observed a relatively greater degree of adaptation over time with anodic stimulation. Bimodal post-stimulus-time histograms were recorded in a small number (2%) of fibers, supporting the hypothesis that both the peripheral (dendritic) and central axonal processes are excitable with the same stimulus polarity, in a limited number of cases. This observation, together with analyses of interactions among measures of latency, threshold, and jitter, is consistent with the hypothesis that, with monopolar intracochlear stimulation, most fibers are stimulated at axonal (modiolar) sites and a minority of fibers nearest the electrode are stimulable at their peripheral processes.

Original languageEnglish (US)
Pages (from-to)197-218
Number of pages22
JournalHearing research
Volume130
Issue number1-2
DOIs
StatePublished - Apr 1999

Keywords

  • Auditory nerve
  • Cat
  • Cochlear implant
  • Electrical stimulation
  • Single fiber recording

ASJC Scopus subject areas

  • Sensory Systems

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