Differential Response of Neurons of the Cochlear Nucleus to TTS-Producing Tones

Abstract

The I/O functions of neurons in the chinchilla cochlear nucleus were measured before and after exposure to 8 min of a 95-dB-SPL tone at the characteristic frequency of the neurons. The exposure produced virtually no change in whole nerve AP but produced 14–19-dB shifts in auditory evoked response thresholds. “Flat primary” and “chopper” neurons showed a general decrease in spontaneous activity (SA), an 8–12-dB decrease in sensitivity, and no truncation of the neuron I/O function. “Pauser” and “primary” units showed little, if any, shift in sensitivity with relatively no change in SA. “On” neurons had higher SA after.exposure; their I/O function was depressed at low intensities and elevated at high intensities relative to the pre-exposure I/O. During the exposure, the activity of “on” neurons dropped below SA, while all other classes of neutrons showed marked increases in activity over the SA rate.