Effects of sound on the tactile perception of roughness in peri-head space

The aim of this study is to investigate whether or not spatial congruency between tactile and auditory stimuli would influence the tactile roughness discrimination of stimuli presented to the fingers or cheeks. In the experiment, when abrasive films were passively presented to the participants, white noise bursts were simultaneously presented from the same or different side, either near or far from the head. The results showed that when white noise was presented from the same side as the tactile stimuli, especially from near the head, the discrimination sensitivity on the cheeks was higher than when sound was absent or presented from a different side. A similar pattern was observed in discrimination by the fingers but it was not significant. The roughness discrimination by the fingers was also influenced by the presentation of sound close to the head, but significant differences between conditions with and without sounds were observed at the decisional level. Thus, the spatial congruency between tactile and auditory information selectively modulated the roughness sensitivity of the skin on the cheek, especially when the sound source was close to the head.