The skin, the largest organ in the human body, envelops us from head to toe and lets us touch, feel and interact with the outside world. But there is a part of this organ even more attuned to the touch than any other.
A new study has revealed how receptive the sensory neurons in our fingers are: as it turns out, we can detect touch on the tiny scale of a single crest of fingerprints.
“A single papillary crest was expected to play a role, but it has not been proven [before]”, Said Ewa Jarocka, co-author of the study at Umeå University in Sweden The guardian.
The sensory neurons attached to the receptors are splattered just below the surface of the skin, allowing us to detect touch, vibration, pressure, pain and more. Our hands alone contain tens of thousands of these neurons, each with receptors on a small surface of the skin, called the receptive field.
To map these fields, the researchers tied the arms of 12 healthy people and stuck their nails to the plastic supports to really make sure they couldn’t move. A machine then rolled small cones 0.4 millimeters wide to about 7 mm apart through its skin (you can see what is seen below) and the team recorded the response of each neuron by an electrode in the arms of the participants.
The configuration. (Jarocka et al., J. Neurosci, 2021)
Specifically, they mapped the most sensitive areas (known as subfields) within these receptive fields.
By calculating the detection areas of sensory neurons and mapping them to the fingerprint, the team found that the width of the detection area was equivalent to the width of a fingerprint ridge.
These subfields also did not move when the machine rolled the dots faster or slower, or changed direction, suggesting that these sensitive areas are anchored to the same ridges of fingerprints.
“We report that the sensitivity of the subfield arrangement for both types of neurons corresponds on average to a spatial period of ~ 0.4 mm and we provide evidence that the spatial selectivity of a subfield arises because its associated receptor organ measures mechanical events limited to a single papillary crest “. the researchers write in their new article.
Receptive fields projected on a fingerprint. (Jarocka et al., J. Neurosci, 2021)
Excitingly, this is the first study to show that our fingerprint crests help us feel the world around us more accurately.
“We have all these multiple access points and each responds to the details of 0.4 millimeters, which is the approximate width of the [fingerprint] crest, ”Jarocka said New scientist.
“Then our brain gets all this information. This really offers an explanation of how we might be so skilled and have such a high sensitivity at our fingertips.”
The research has been published in The Journal of Neuroscience.