Visual stimuli approaching toward the body influence temporal expectations about subsequent somatosensory stimuli.

The present study investigated whether visual stimuli approaching the body influence temporal expectations about subsequent somatosensory stimuli. To examine this question, we recorded event-related brain potentials (ERPs) during a simple reaction time task using somatosensory stimuli. Fourteen participants were asked to place their arms on a desk, and three light-emitting diodes (LEDs) were placed at equal distances between their arms. Each trial was composed of three visual stimuli (i.e., LEDs), and one subsequent electrical stimulus (i.e., somatosensory stimulus) to one wrist. The stimulus onset asynchrony (SOA) between the visual stimuli was set to 1000ms. The SOA between the third visual stimulus and the somatosensory stimulus was set to 1000ms (standard; p=0.75), 500ms (early deviation; p=0.125), and 1500ms (late deviation; p=0.125). In the approach condition, the left, center, and right LEDs (or reverse) were turned sequentially toward the wrist to which the somatosensory stimulus was presented. In the neutral condition, the center LED was flashed three times. The N1 amplitudes for early deviations of stimuli were larger under the approach condition than under the neutral condition. These results show that prior visual stimuli facilitate temporal expectations about subsequent somatosensory stimuli, i.e., visual stimuli approaching toward the body facilitate the processing of early deviant stimuli. The present study indicates the existence of a function of supramodal temporal expectation and detection of deviation from this expectation using the approach of visual stimuli toward the body.