The skin – the largest organ in the human body – envelops us from head to toe, allowing us to touch, feel and interact with the outside world. But there is a part of that organ that is more attuned to touch than any other.
A new study has revealed just how responsive the sensory neurons in our fingers are: It turns out that we can detect touch on the miniscule scale of a single fingerprint edge.
You would expect a single papillary ridge to play a role, but that hasn’t been proven [before], ”Said Ewa Jarocka, co-author of the study from Umeå University in Sweden The Guardian
Sensory neurons attached to receptors are located just below the surface of the skin, allowing us to detect touch, vibrations, pressure, pain, and much more. Our hands alone contain tens of thousands of these neurons, each with receptors on a small area of the skin, called a receptive field.
To map these fields, the researchers tied the arms of 12 healthy people and taped their fingernails to plastic containers to make sure they couldn’t move. A machine then spun tiny, 0.4 millimeter wide cones about 7mm apart across their skin (you can see what that looks like below) and the team recorded the response of each neuron using an electrode in the participants’ arms .
The set-up. (Jarocka et al., J. Neurosci, 2021)
In particular, they mapped the more sensitive zones – known as subfields – within these receptive fields.
By calculating the sensory neuron detection areas and mapping them on the fingerprint, the team found that the width of the detection area was equal to the width of one fingerprint edge.
These subfields also did not move when the machine moved or changed direction faster or slower, suggesting that these sensitive areas are anchored to the fingerprint ridges themselves.
“We report that the sensitivity of the subfield setup for both neuron types corresponds on average to a spatial period of ~ 0.4 mm and provide evidence that the spatial selectivity of a subfield arises from the associated receptor organ measuring mechanical events confined to a single papillary ridge. , the researchers write in their new paper.
Receptive fields projected on a fingerprint. (Jarocka et al., J. Neurosci, 2021)
Excitingly, this is the first study to show that our fingerprint backs help us sense the world around us more accurately.
“We have all these different hot spots, and each one responds to the 0.4 millimeter detail, which is roughly the width of the [fingerprint] ridge, ”Jarocka said New scientist
“Then our brains receive all that information. This really provides an explanation for how it is possible for us to be so agile and have such a high sensitivity in our fingertips.”
The research is published in The Journal of Neuroscience