THE EFFECTS OF MASKING ON VIBROTACTILE TEMPORAL SUMMATION IN THE DETECTION OF SINUSOIDAL AND NOISE SIGNALS

Thresholds for the detection of vibrotactile signals of varied duratio n applied to the thenar eminence were measured in the absence of and i n the presence of a masking stimulus. Signals were 250- and 500-Hz sin usoids and noise bursts with bandwidth limited to 250-1000 Hz. The mas king stimulus was either a 250-Hz sinusoid, which was presented in pha se with the signal when it was sinusoidal, or noise. Changes in thresh old as a function of changes in signal duration were found which were predicted accurately from Zwislocki's theory. [J. Acoust. Soc. Am. 32, 1046-1060 (1960)] of temporal summation when the signal was detected by the Pacinian channel, but not when it was detected by a non-Pacinia n channel (NP). However, when either the signal or the masking stimulu s or both were noise, NP thresholds were affected by changes in signal duration. Only when the signal and masking stimuli were both sinusoid s were NP thresholds independent of signal duration. It is concluded t hat signal duration effects in the NP channel are dot due to temporal integration, but rather to increases in information about the signal c ontent provided to the subject as exposure duration is increased.