4aPP14. Psychophysical evidence of excitatory connections across auditory frequency channels.

Session: Thursday Morning, May 16

Time: 11:30

Author: Beverly A. Wright
Location: Keck Ctr., P.O. Box 0732, Univ. of California, San Francisco, CA 94143-0732


A simultaneously masked auditory signal becomes easier to detect as its onset is delayed from masker onset. This ``enhancement effect'' depends upon masking components presented outside of the signal's frequency channel, indicating the participation of an across-channel process. The nature of this process has not been clearly established due to the difficulty of separating the influence of excitation and inhibition in simultaneous masking. Here, the forward-masked threshold of a 20-ms, 1000-Hz tone was determined in the presence of one or two masking tones [M1 (1000 Hz, 50 dB) and M2 (variable from 500 to 3000 Hz, 70 dB)]. When the masker duration was 500 ms, adding M2 to M1 reduced signal threshold when M2 was presented at 1150 Hz (suppression), but had no influence on performance when M2 was above about 1300 Hz. In contrast, when the masker duration was 40 ms, adding M2 to M1 did not lower threshold at 1150 Hz, and always increased threshold when M2 was presented above 1300 Hz. This latter threshold increase was reduced when a third masking tone presented at 1150 Hz was added to M1 and M2. These results suggest that the across-channel process involved in the enhancement effect is excitatory, adapts, and is moderated by suppression. [Work supported by NIDCD.]

from ASA 131st Meeting, Indianapolis, May 1996