ASA 127th Meeting M.I.T. 1994 June 6-10

4aPP21. Does recovery from forward masking reflect two neural channels?

Lance Nizami

Bruce A. Schneider

Dept. of Psychol., Erindale College, Univ. of Toronto, 3359 Mississauga Rd., Mississauga, ON L5L 1C6, Canada

Recovery rates differ significantly [E. M. Relkin and J. R. Doucet, Hear. Res. 55, 215--222 (1991)] for nerve fiber groups believed to be separate channels for loud and soft sounds [e.g., Winslow et al., in Auditory Processing of Complex Sounds (Erlbaum, Hillsdale, NJ, 1987), pp. 212--224]. Such differences could produce two distinct portions in the auditory recovery curve. Forward-masked detection thresholds were obtained from three experienced listeners using a two-interval forced-choice task, at masker-target time gaps (recovery times) of 0--10 ms with a resolution of 1 ms or less. The masker, a 97 dB SPL, 2-kHz, 200-ms tone, preceded a 2-kHz Gaussian-shaped tone pip ((sigma)=0.5 ms). A cusp appeared in the curve relating forward-masked thresholds to recovery time at 3--6 ms, indicating that recovery followed a two-part decay curve. Forward-masked thresholds rise over 0--2 ms replicating a pattern found earlier [H. Duifhuis, J. Acoust. Soc. Am. 54, 1471--1488 (1973); M. J. Penner, J. Acoust. Soc. Am. 56, 179--182 (1974)]. [Work supported by NSERC.]