Researchers have long known that the sense of touch is a result of sensory receptors sending signals through the nerve cells to the brain, but the exact mechanisms behind this process have been unclear. Now, scientists from Columbia University Medical Center in New York, NY, say they have identified the key cells involved in touch sensation.
This is according to a study recently published in the journal Nature.
The research team, led by Dr. Ellen Lumpkin, associate professor of somatosensory biology at Columbia University Medical Center, says the findings could lead to the development of new "smart" prosthetics that restore sense of touch for limb amputees, and may even lead to new treatments for skin diseases, such as chronic itch.
According to the investigators, scientists have increasingly learned how the senses of sight, smell, taste and hearing work, but that understanding of the cells and molecules responsible for initiating the sense of touch has been lacking.
With this in mind, the research team set out to learn more about the process.
Merkel cells in skin work with neurons to allow perception of sensitive touch
Using optogenetics on mice - a technique that uses light to switch neurons on and off on demand - the researchers were able to see how skin cells communicate and function. This study is the first to use such a method.
The scientists found that Merkel cells in our skin are able to sense touch and work closely with the skin's neurons to allow us to perceive fine details and textures. In other words, the Merkel cells in our skin interact with neurons to enable us to recognize sensitive touch.
A video showing the Merkel cells responding to touch can be viewed below:
Commenting on the findings, Dr. Lumpkin says:
"These experiments are the first direct proof that Merkel cells can encode touch into neural signals that transmit information to the brain about the objects in the world around us."
She adds that not only do these findings advance the understanding of the sense of touch, but they could also prompt further research into loss of sensitive-touch perception.
Many conditions, such as diabetes, some chemotherapy treatments for cancer and the normal aging process, are all known to lower perception of sensitive touch. Dr. Lumpkin says that Merkel cells start to diminish when a person hits their early 20s - the same time as a person's tactile acuity (sharpness of sense of touch) begins to decline.
This picture shows Merkel cells (pink) and neurons (blue) under the skin surface. These interact to allow us to feel sensitive touch.
Image credit: Kara Marshall
Because of this, Dr. Lumpkin says the team is interested in looking at whether loss of Merkel cells is associated with loss of function during the aging process.
In collaboration with investigators from the Scripps Research Institute in La Jolla, CA, the research team conducted a second study that identified a touch-activated molecule in skin cells, called Piezo2. The researchers say the discovery of this molecule could advance the field of touch perception even further.
In addition, the researchers say that using the optogenetics method could lead to the discovery of other types of skin cells that play a part in touch sensation, and even skin irritation, such as itch.
"It's an exciting time in our field because there are still big questions to answer, and the tools of modern neuroscience give us a way to tackle them," concludes Dr. Lumpkin.
Medical News Today recently reported on a study revealing that babies positively respond to pleasant touch, which helps build bonds between infants and parents.