Reductions in gain from pre-masker stimulation at the signal frequency

Abstract

Normal hearing individuals can detect a short duration signal at a lower signal-to-masker ratio when the signal is delayed from masker onset compared to near it. This is often referred to as the temporal effect. This effect is interesting because it may be related to changes in cochlear gain. It has been proposed that gain is high at masker onset and decreases, in a frequency specific manner, through the course of the masker. If this hypothesis was true, it is expected that frequency selectivity also decreases through the course of the masker. Using a forward masking paradigm, the current study examines the hypothesis that frequency selectivity decreases with pre-masker stimulation at the signal frequency. Growth of masking (GOM) functions and psychophysical tuning curves (PTC) were measured for the signal using a short masker preceded by a long duration precursor set at the signal frequency or well below the signal frequency. Preliminary results reveal a relatively broader PTC and a steeper GOM function when the precursor was at the signal frequency and are consistent with the hypothesis that preceding stimulation at the signal frequency reduces gain. [Work supported by the Hazelton Fund.]