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 no rmal-hearing, human subjects. The CAP was recorded using a wick electr ode placed on the tympanic membrane. The effects of a 4000-Hz, 97-dB S PL conditioning stimulus on CAP amplitude in response to a 4000-Hz pro be 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 interv al of 1359 ms, similar to that observed in chinchilla (Relkin, E.M., D oucet, J.R., Sterns, A., 1995. Recovery of the compound action potenti al following prior stimulation: evidence for a slow component that ref lects recovery of low spontaneous-rare auditory neurons, Hear. Res. 83 , 183-189). The present results are interpreted as a consequence of th e slow recovery of low spontaneous-rate (SR), high threshold neurons f rom prior stimulation (Relkin, E.M., Doucet, J.R., 1991. Recovery from prior stimulation. I: Relationship to spontaneous firing rates of pri mary auditory neurons. Hear. Res. 55, 215-222) and may provide indirec t physiological evidence for the existence of a class of low-SR audito ry neurons in humans. (C) 1998 Published by Elsevier Science B.V. All rights reserved.