Action potentials in the cat at low sound intensities: Thresholds, latencies, and rates of change

Abstract

The interpretation of whole-nerve action potentials is a topic of increasing importance in both clinical and research settings. This effort is hampered by a lack of data on the action potential that are theoretically interpretable and systematically measured over a wide range of frequencies and at low sound intensities. The thresholds, latencies and rates of change in the whole-nerve action potential were measured in response to constant-spectral-width tone pips at 8 frequencies between 0.5-20 kHz in the cat ear. These quantities were calculated by a linear regression technique from round-window potentials in 28 normal ears. They were consistently within approximately 18 dB of previously published behavioral measures, a difference attributable to temporal integration. The interanimal variability had a SD of about 5 dB and the intra-animal variability was extremely low. The growth of amplitude across frequencies, the rate of change of latency with intensity changes and the latency at threshold demonstrated orderly relationships. The data were all consistent with contention that the potentials were being produced by a single population of cells located at a place consistent with the frequency of the eliciting tone. The methods used provide exceedingly stable measures and should be applicable in clinical and research settings.