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

2aPP31. Changes in cochlear frequency selectivity caused by sound stimulation of the contralateral ear.

Deirdre M. Williams

Ann M. Brown

Lab. of Exp. Psychol., Univ. of Sussex, Brighton BN1 9QG, England

Suppression of the 2f[sub 1]-f[sub 2] distortion product by a third ipsilateral suppressor tone was measured in the presence and absence of contralateral broadband noise. The amount of ipsilateral suppression varied with suppressor frequency but was maximum close to the f[sub 2] primary frequency as previously demonstrated using similar stimulus parameters [A. M. Brown and D. T. Kemp, Hear. Res. 13, 29--37 (1984); F. P. Harris et al., Hear. Res. 64, 133--141 (1992)]. In general, the amount of ipsilateral suppression of the distortion product was reduced under contralateral stimulation. This interaction may indicate a common mechanism for ipsilateral and contralateral suppression. The decrease in ipsilateral suppression under contralateral stimulation was most pronounced at the peak of the distortion tuning curves and this produced some broadening of the tuning curves. In the majority of tuning curves, the peak ipsilateral suppression frequency was observed to shift upwards. These results suggest that contralateral stimulation alters the frequency-selective properties of the cochlear response. [Work supported by the Wellcome Trust.]