James C. Makous
Inst. for Sensory Res., Syracuse Univ., Merrill Ln., Syracuse, NY 13244-5290
George A. Gescheider
Hamilton College, Clinton, NY 13323
Stanley J. Bolanowski
Inst. for Sensory Res., Syracuse Univ., Syracuse, NY 13244-5290
Four subjects were tested with a forward masking paradigm to determine the time course of masking in the Pacinian (P) and a non-Pacinian (NPI) channel. Stimuli presented to the thenar eminence were either centered below 27 Hz or at 500 Hz to preferentially activate the NPI or P channels, respectively. Two-interval forced-choice tracking was used to measure thresholds. A masking stimulus was presented 100 ms after each interval onset and a test occurred in one of the two intervals at some specified delay (delay t) relative to the masking stimulus. Delta t was varied from 10 to 1000 ms and the masking stimulus level varied from 5 to 25 dB above thresholds in 5-dB steps. The results showed that the masking functions varied significantly with delta t. At longer delta t's there was less masking that followed an exponential decay. The results from the individual channels differed from each other with respect to the slope of the masking functions and the exponential decay of masking with delta t. The time constants for the PC channel ranged from 20 to 40 ms, whereas the time constants for NPI ranged from 50 to 120 ms. [Work supported by NIH, NIDCD.]