"Let Me Soothe It" Is Not Just a Saying: The Neuroscience Behind a Mother's Touch

Pain Signals Weakened by Stimulation of Specific Tactile Nerves
New Treatment Methods Expected Using Electricity and Vibration

A study has found that a mother's hand, which can calm a crying child with just a gentle, warm touch even without any medicine or special treatment, actually has a real effect. The research team announced that there is neuroscientific evidence for the so-called "mother's hand," which has long been regarded merely as a symbol of love and comfort.

On July 14, the Yomiuri Shimbun reported, citing research from Kyushu University in Japan, that Professor Makoto Tsuda and graduate student Daichi Sueto, along with their team, identified a specific group of sensory nerves involved in pain suppression among those that transmit skin touch signals to the spinal cord through mouse experiments. The research is scheduled to be published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS) by July 19, under the title "A primary afferent sensory neuron population mediating touch-induced analgesia through pain defense coping behaviors in mice."

Tripled Pain Behaviors After Eliminating Specific Sensory Nerves

Just as humans and animals instinctively touch or rub an injured area, mice also repeatedly licked a paw that received a painful stimulus. Although substances in saliva may influence wounds, it had not been clearly demonstrated whether the act of continuous "contact stimulation" from the tongue touching the skin itself reduces pain.

The research team focused on a specific subpopulation of sensory nerves in mice distinguished as "Npy2r-Cre nerves." This group refers to sensory nerves in experimental mice identified using the regulatory region of the neuropeptide Y receptor 2 gene. When the team removed this group of nerves and then applied a painful stimulus to the paw, the time mice spent licking their paw increased significantly—about three times longer than in normal mice, according to Japanese media reports.

Conversely, when only this particular nerve group was selectively stimulated, the duration of paw licking dropped to less than half of that observed before. The process through which pain signals generated in the skin are transmitted from the spinal cord to the brain was also weakened. The researchers concluded that the contact signal that occurs when the mouse licks its wound activates this sensory nerve, and this signal puts a sort of "brake" on the pain transmission circuit in the spinal cord.

Tactile Signals That "Close the Gate of Pain"

Nerves that transmit pain and those that detect touch information travel along separate pathways. Pain information generated at the skin excites spinal cord neurons and is then relayed to the brain, where the sensation of "pain" arises. However, when a touch signal occurs simultaneously, inhibitory neural circuits in the spinal cord can be activated, reducing the transmission of pain information.

This aligns with the "Gate Control Theory of Pain" proposed in 1965. Academic materials from the Korean Neurological Association also explain that tactile information entering through thick, myelinated sensory nerves can activate inhibitory neurons in the spinal cord to reduce pain transmission. The photo is unrelated to the specific content of the article. Pixabay

This aligns with the "Gate Control Theory of Pain" proposed in 1965. Academic materials from the Korean Neurological Association also explain that tactile information entering through thick, myelinated sensory nerves can activate inhibitory neurons in the spinal cord to reduce pain transmission. The practice of rubbing a painful area or using transcutaneous electrical nerve stimulation (TENS) can also be partially explained by this theory.

Previously, in 2017, the international journal Neuron published a study reporting that when nerves detecting gentle touch—so-called low-threshold mechanoreceptors—were activated at the same time as pain nerves, mice displayed a reduced acute mechanical pain response. The significance of the new research lies in its further step: it has identified, more specifically, the group of sensory nerves that mediate pain relief during "self-soothing behaviors" such as licking an injured area in animals.

Can "Healing Hands" Be Recreated with Electricity or Vibration?

The Kyushu University research team plans to investigate whether there is a group of nerves in humans with similar functions to those found in mice. If specific nerves can be effectively stimulated, this could be developed into a medical device that uses electricity, vibration, or pressure to reduce pain during injuries, injections, or treatments.

However, this study remains an animal experiment using only mice. It does not mean that all pain disappears whenever a mother touches an injury, nor does it suggest that simple rubbing can replace painkillers or medical treatments. Actual pain experienced by humans is influenced by a variety of factors, including not only peripheral nerves and the spinal cord but also anxiety, memory, attention, and emotional stability. The researchers also explained that a gentle touch may reduce pain by shifting one's focus away from pain or providing a sense of comfort and safety. They plan to further investigate not only the direct neural inhibition caused by contact signals but also these psychological and emotional factors.

Professor Tsuda said, "There is a traditional Japanese term 'teate,' which means 'to heal by laying on hands.' We have long known from experience that touching an aching area reduces pain," adding, "This research may have uncovered one of the mechanisms explaining why simple touch relieves pain."

This content was produced with the assistance of AI translation services.