Hugging, holding hands, and stroking give us a psychological boost that is known to be important for emotional well-being and healthy development.
But until now it was unclear why this kind of touch gives us pleasure.
Now researchers at Washington University School of Medicine in St. Louis have identified a neuronal circuit and a neuropeptide – a chemical messenger that transmits signals between nerve cells – that transmit the sensation known as “pleasant touch” from the skin to the brain.
They claim that the discovery of the neural circuit and a neuropeptide in mice could help scientists better understand and treat disorders characterized by touch avoidance and impaired social development in humans, including autism spectrum disorders.
Pleasant touch sensations like a hug give us a psychological boost that is known to be important for emotional well-being and healthy development
A pleasant sense of touch is very important in all mammals. Now researchers have identified a neural circuit that relays this sensation from the skin to the brain
“A pleasant sense of touch is very important in all mammals,” said Dr. Zhou-Feng Chen, director of the Center for the Study of Itch & Sensory Disorders at Washington University, who led the study.
“Babies are nurtured primarily through touch. Holding the hand of a dying person is a very powerful, comforting force. Animals groom each other. People hug and shake hands. Massage therapy reduces pain and stress and may provide benefits to patients with psychiatric disorders.
“In these experiments in mice, we identified an important neuropeptide and hardwired neural pathway dedicated to this sensation.”
Chen’s team found that mice lacking the neuropeptide called prokinecticin 2 (PROK2) could not perceive pleasant touch cues, but continued to respond normally to itch and other stimuli.
“Now that we know which neuropeptide and which receptor transmit only pleasant touch sensations, it might be possible to amplify pleasant touch signals without disturbing other circuits,” he said.
‘[This] is crucial as pleasant touch boosts several hormones in the brain that are essential for social interactions and mental health.’
Chen’s team discovered that mice lacking PROK2 avoided activities like grooming and showed signs of stress not seen in normal mice.
The researchers also found that mice that lacked pleasant touch response from birth exhibited stronger stress responses and exhibited stronger social avoidance behaviors than mice whose pleasant touch response was blocked in adulthood.
Chen said the find underscores the importance of maternal touch in offspring development.
Holding the hand of a dying person is a very “powerful, comforting force,” researchers say
3D printed fingertips can “feel” like human skin.
British scientists have created a 3D-printed fingertip that has a sense of touch like human skin.
University of Bristol researchers found that the new fingertip was able to generate artificial nerve signals similar to those generated by signals from various human nerve endings.
They hope it could eventually help improve prosthetics for humans by creating artificial skin that’s just as good as real skin.
Read more here
“Mothers love to lick their puppies, and adult mice often groom each other for good reasons, such as promoting emotional bonding, sleep and stress reduction,” he said.
“But these mice avoid it. Even when their cagemates try to groom them, they withdraw. They don’t clean other mice either. They are withdrawn and isolated.”
One of the challenges of the study, Chen says, was figuring out how to get mice to allow themselves to be touched — and interpreting how certain types of touch made the mice feel.
“If an animal doesn’t know you, it usually shies away from any kind of touch because it may see it as a threat,” he said.
“Our difficult task was to design experiments that helped overcome the animals’ instinctive avoidance of touch.”
To get the mice to cooperate – and to see if they found touch pleasant – the researchers kept the mice away from their cagemates for a period of time, after which the animals were more receptive to being stroked with a soft brush, similar to Pets that are petted and cared for.
After several days of such brushing, the mice were then placed in a two-chamber environment. The animals were brushed in a chamber. There was no stimulus in the other chamber.
Given the choice, the mice went into the chamber where they were brushed.
Mice engage in a grooming behavior and experience a phenomenon that researchers call pleasant touch. The findings could eventually help scientists better understand and treat disorders characterized by touch avoidance and impaired social development.
Next, Chen’s team began identifying the neuropeptides that were activated by pleasant brushing.
They found that PROK2 communicated pleasant touch signals to the brain in sensory neurons and the spinal cord neural circuitry that expresses its receptor (PROKR2).
In further experiments, they found that the neuropeptide they focused on was not involved in transmitting other sensory signals, such as itch.
Chen, whose lab was the first to identify a similar, dedicated pathway for itch, said pleasurable touch sensations are transmitted by an entirely different, dedicated network.
“Just as we have itch-specific cells and peptides, we have now identified pleasingly touch-specific neurons and a peptide to transmit these signals,” he said.
The study was published in the journal Science.
YOU COULD SOON FEEL PAIN IN THE METAVERSUM
The idea of a bracelet that can mimic pain in the metaverse might sound like a concept from Black Mirror’s latest series.
But thanks to a Japanese start-up, the spooky device has become a reality.
H2L, a Tokyo-based Sony-backed company, has developed a bracelet that uses electrical stimulation to induce physical pain.
Dubbed the UnlimitedHand, the bracelet features muscle motion sensors that recognize your hand gestures and position, allowing your avatar to accurately copy your movements in the Metaverse.
It also uses electrical stimulation to manipulate arm muscles and mimic sensations.
“Feeling pain allows us to turn the metaverse world into a real world [world]with an increased sense of presence and immersion,’ said Emi Tamaki, CEO and co-founder of H2L.