Recovery of the human compound action potential following prior stimulation.

The recovery from prior stimulation of the compound action potential (CAP) was measured using a forward masking stimulus paradigm in four normal-hearing, human subjects. The CAP was recorded using a wick electrode placed on the tympanic membrane. The effects of a 4000-Hz, 97-dB SPL conditioning stimulus on CAP amplitude in response to a 4000-Hz probe were measured as a function of conditioner-probe interval for three probe levels. The normalized probe response amplitude was completely recovered to the control values at an average conditioner-probe interval of 1359 ms, similar to that observed in chinchilla (Relkin, E.M., Doucet, J.R., Sterns, A., 1995. Recovery of the compound action potential following prior stimulation: evidence for a slow component that reflects recovery of low spontaneous-rate auditory neurons, Hear. Res. 83, 183-189). The present results are interpreted as a consequence of the slow recovery of low spontaneous-rate (SR), high threshold neurons from prior stimulation (Relkin, E.M., Doucet, J.R., 1991. Recovery from prior stimulation. I: Relationship to spontaneous firing rates of primary auditory neurons. Hear. Res. 55, 215-222) and may provide indirect physiological evidence for the existence of a class of low-SR auditory neurons in humans.