Effects of contralateral noise on measurement of the psychophysical tuningcurve

The effects of the addition of contralateral noise on the psychophysical tu ning curve (PTC) were examined in subjects with normal hearing. The masking threshold of the tail part of the PTC tended to decrease with the addition of contralateral noise, although the threshold reduction was usually less than 5 dB. On the other hand, the effects of contralateral noise were relat ively small around the tip of the PTC contour. Focusing on the effects of c ontralateral noise on the masking threshold at the tail part of the PTC, th e effects of changing the time between initiation of masking the tone and t he presentation of the masked probe tone on the threshold reduction at the tail part of the PTC were also observed. The results indicate that the redu ction of the masking threshold by the addition of contralateral noise tende d to be larger when the presentation of the signal tone was delayed after t he onset of the masker. Usually, when the signal tone was presented under c onditions of the forward masking paradigm, the reduction of the threshold w as most remarkable. Results obtained in the present study are discussed bas ed on the known characteristics of the olivocochlear (OC)-efferent fibers a ctivated by contralateral noise. (C) 2000 Elsevier Science B.V. All rights reserved.