Study Identifies 16 Nerve Cell Types Involved in Human Sense of Touch

A study published in Nature Neuroscience has revealed the intricate nature of the human sense of touch, identifying 16 distinct types of nerve cells involved in somatic sensation. This collaborative research, conducted by scientists from Linköping University, Karolinska Institutet, and the University of Pennsylvania, challenges the conventional understanding of how we perceive touch, temperature, and pain.

The study employed deep RNA sequencing to analyze gene expression in individual nerve cells, grouping those with similar profiles into distinct sensory nerve cell types. Researchers then used microneurography to link gene expression with cellular function, allowing them to "listen in" on individual nerve cells as they responded to various stimuli.

This approach led to several surprising discoveries. For instance, a nerve cell type associated with pleasant touch was found to react unexpectedly to heating, capsaicin, and cooling. As co-senior author Håkan Olausson explains, "For ten years, we've been listening to the nerve signals from these nerve cells, but we had no idea about their molecular characteristics. In this study, we see what type of proteins these nerve cells express as well as what kind of stimulation they can respond to, and now we can link it. It's a huge step forward."

The research also compared findings across humans, mice, and macaques, revealing both similarities and significant differences. Notably, humans possess a higher proportion of rapidly conducting pain-sensing nerve cells compared to mice, possibly due to differences in body size and the need for faster signal transmission.

This study provides a comprehensive view of the human sense of touch and sets the stage for further exploration of each identified nerve cell type. As Associate Professor Saad Nagi concludes, "There's a common perception that nerve cells are very specific—that one type of nerve cell detects cold, another senses a certain vibration frequency, and a third reacts to pressure, and so on. It's often talked about in those terms. But we see that it's a lot more complicated than that."