Effect of gentle cutaneous stimulation on heat-induced autonomic response and subjective pain intensity in healthy humans

The present study examined whether touch influences the autonomic responses and subjective pain intensity induced by noxious heat stimulation in humans. Heart rate and digital pulse wave were recorded. Heat stimulation was applied to the right plantar foot before, during, and after touch. Subjective pain intensity was evaluated using a visual analog scale (VAS). Touch was applied over the right medial malleolus for 10 min. Two types of touch were employed in a cross-over double-blinded randomized manner. When touch was applied with a soft elastomer brush, heat-induced autonomic responses attenuated significantly, while VAS scores were unchanged. In contrast, touch with a flat disc was ineffective for any measurement. Participants hardly perceived a difference in the texture of the touching materials. The present study result suggests there are mechanisms in conscious humans where some sort of touch inhibits nociceptive transmission into autonomic reflex pathways independent of sensation and cognition.