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 one part of the organ that is even more customized than any other.
A new study has revealed how receptive the sensory neurons are in our fingers: as it turns out, we can detect touch on the minuscule scale of a single fingerprint back.
‘You would expect a single papillary ridge to play a role, but it has not been shown [before], “Tells Ewa Jarocka, co-author of the study from Umeå University in Sweden The guardian.
Sensory neurons attached to receptors are dotted just below the skin’s surface, 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 a receptive field.
To map these fields, the researchers tied the arms of 12 healthy people and glued their fingernails to plastic containers to make sure they could not move. A machine then drove small, 0.4 millimeter wide cones about 7 mm across their skin (you can see what it looks like below) and the team recorded the response of each neuron using an electrode in the arms of the participants.
The setup. (Jarocka et al., J. Neurosci, 2021)
They specifically mapped the more sensitive zones – known as subfields – in these receptive fields.
By calculating the sensory neuron detection areas and mapping on the fingerprint, the team found that the width of the detection area was equal to the width of one fingerprint reef.
These subfields also did not move when the machine moved faster or slower with the dots or changed direction, indicating that these sensitive areas were anchored to the fingerprint edges themselves.
“We report that the sensitivity of the subfield arrangement for both neuron types corresponds on average to a spatial period of ~ 0.4 mm and provide evidence that a subfield’s spatial selectivity arises because the associated receptor organ measures mechanical events that are limited to ‘ a single papillary ridge, “the researchers write in their new paper.
Reception fields projected on a fingerprint. (Jarocka et al., J. Neurosci, 2021)
Strikingly, this is the first study that has shown that our fingerprint edges help us to feel the world around us more closely.
“We have all those multiple hotspots, and each one responds to the 0.4 millimeter detail, which is the estimated width of the [fingerprint] reef, ”Jarocka said New scientist.
“Then our brain receives all the information. It gives an explanation for how it is possible that we are so agile and have such a high sensitivity in our fingers.”
The research was published in The Journal of Neuroscience.