Absolute Behavioral Auditory Thresholds in Mice

Abstract

The experiment was designed to obtain behavioral measures of absolute auditory thresholds and to compare them with cochlear potentials and with single-unit eighth-nerve-fiber thresholds. Mice were selected because certain strains display pathological conditions that appear similar to some congenital auditory defects found in humans. The present study deals only with normal mice. Results of avoidance and escape-conditioning techniques are compared, as are results of the psychophysical method of limits and the method of constant stimuli. The animal was trained to avoid shock (in avoidance-conditioning) by responding to the tone alone, or to terminate shock (in escape-conditioning) by making one response to tone plus shock and another to shock alone. The range of frequencies tested was 500–32 000 cps. The test chamber was placed inside a sound-shielded box. Tones were transmitted from one oscillator outside the box. The intensity of all tones and the noise level in the test chamber were measured by a wave analyzer. Shock was administered through the grid floor. Results are discussed in terms of the minimum sound intensity required at the various frequencies, response latency, and response variability. Some problems inherent in the training techniques are described.