Auditory Facilitation following Stimulation at Low Intensities

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Abstract
Auditory thresholds may become lower (improve) following stimulation by sound of low intensity. This shift in threshold was determined by comparing the reference threshold of a test pulse, presented alone, to the threshold for the test pulse preceded by a stimulating pulse. Duration, intensity, and frequency of the stimulating pulse were controlled, as were duration and frequency of the test pulse and duration of the interval between pulses. For pulses of 1000 cps, facilitation, or a lowering of the threshold, consistently follows stimulation by sound of 25 db SL or less; the lower the stimulating intensity, the more widespread the facilitation, over the various poststimulatory intervals tested. Facilitation reaches a maximum of 5 to 7 db 160 msec after the termination of the stimulating pulse, although some negative shift in threshold occurs after the longest interval (2 sec). Stimulation by white noise may depress the threshold for a pure tone, although a pure tone seems to have no effect upon the threshold for a white noise. When the stimulating pulse is a 1000‐cps tone, facilitation occurs for test tones between 500 and 2000 cps. The maximal shift is at 160 msec for all test tones except 2000 cps. The nature of the facilitatory process, auditory or attentional, and its locus, whether peripheral or central, are discussed.

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