Contralateral enhancement and suppression of vibrotactile sensation

A psychophysical matching procedure was used to measure the effect of a conditioning stimulus on the vibrotactile sensation magnitude of a test stimulus. When both stimuli were applied to the thenar eminence of the same hand, the conditioning stimulus enhanced the sensation magnitude of the test stimulus. Enhancement was also observed when the test stimulus was on the thenar eminence and the conditioning stimulus was either on the contralateral thenar eminence, the ipsilateral middle finger, or the contralateral middle finger. When the conditioning and test stimuli were applied to separate sites, enhancement was maximal when At between the stimuli was 150 msec. At Ate less than 100 msec, suppression was observed. Enhancement and suppression were observed only when the frequencies of the two stimuli were within the same vibrotactile information processing channel.