Central Nervous System Responses to Comfortable Thermal Stimuli to the Soles of the Feet with Simultaneous Presentation of Other Sensory Stimuli

Abstract

The current study sought to examine differences in physiological responses to comfortable thermal stimuli applied to the soles of the feet during the simultaneous presentation of other sensory stimuli. As relaxing stimuli, underwater movie footage, classical music, light blue illumination, vibration of the trunk, and the odor of grapefruit oil were each presented simultaneously with a thermal stimulus. Electroencephalography of parietal and cerebral blood flow in the prefrontal cortex were measured. An increase in α-wave activity and a decrease in cerebral blood flow were found for all combinations of stimuli compared with baseline. Additionally, the results revealed differences in response speed depending on the stimulus presentation condition. However, the tendency suggesting a difference in response times depending on the stimulus condition was similar to that of the thermal stimulus alone. The results indicated that thermal stimulation has a substantial effect on the feeling of relaxation.