The approach of visual stimuli influences expectations about stimulus types for subsequent somatosensory stimuli.

It is known that perceiving a visual stimulus influences the processing of subsequent somatosensory stimuli. In particular, an emotion-laden visual stimulus influences the processing of types of subsequent somatosensory stimuli. Additionally, visual stimuli approaching the body facilitate spatial and temporal expectations about subsequent somatosensory stimuli even if the visual stimuli do not contain emotional information; however, it remains unclear whether the approach of non-emotional visual stimuli also influences such expectations. To investigate whether the approach of non-emotional visual stimuli influences expectations about types of subsequent somatosensory stimuli, event-related brain potentials (ERPs) during a simple reaction time task using somatosensory stimuli were recorded. Specific colors of visual stimuli and types of somatosensory stimuli were combined to form congruent and incongruent trials. In the congruent trials, specific combinations (e.g., blue color and a single pulse) were presented (80% of the trials), whereas in the incongruent trials, different combinations (e.g., blue color and a train pulse) were presented (20% of the trials). Under the approach condition, the visual stimuli sequentially approached the wrist to which the somatosensory stimulus was presented. In the neutral condition, the visual stimuli did not approach. The results of the ERP analysis showed that incongruence evoked a P3 response with larger amplitude under the approach condition than under the neutral condition. This result suggests that visual stimuli that approach the body function as clues regarding the types of subsequent somatosensory stimuli even if the visual stimuli do not contain emotional information.