Latency of Action Potentials in the Cochlea of Guinea Pig

Abstract

The latency of the well-synchronized whole-nerve action potential (AP) in the cochlea of the guinea pig includes both neural and traveling-wave delays. The latency varies with the intensity and with the frequency of the acoustic stimulus. Selective local interference with the response was produced by (1) selective masking, (2) local fatigue of sensory elements, and (3) local injection of drugs. Such interference in the basal turn prolonged the latency of the AP response. Interference in higher turns suppressed later portions of the response without changing the modal latency. Apparently nearly all of the well-synchronized AP is due to neurons that arise in the first turn of the cochlea, regardless of the frequency of stimulation. The traveling wave delay appears as a component of latency only in the smaller AP responses that remain after the impulses arising in the first turn are suppressed. Apparently information about the time of onset of an acoustic signal is delivered to the central nervous system primarily by the well-synchronized initial portion of the AP response. (Supported by the Office of Naval Research, Contract N6onr 272.)