Your fingertips remember the things you touch, and this characteristic affects the way sensory information is transmitted to the brain.
New research demonstrates how important this concept could be to a person’s ability to perform everyday tasks.
The brain must ensure that the hands apply the correct amount of force relative to the object being touched or picked up.
The relationship between the brain and the fingertips
Tactile neurons in the fingertips constantly register the force being applied to our hands by sensing skin deformations, information they then relay back to the brain.
“The viscoelasticity of the human fingertip means that any deformation caused by a force acting on the fingertip lasts longer than the force itself,” Hannes Saal, a senior lecturer in the Department of Psychology at the University of Sheffield, said in a press release .
“Therefore, residual deformations from previous forces will affect how the fingertip mechanically reacts when subjected to a new force.
However, the extent to which this physical memory influences tactile neuron signaling during natural hand use is not fully understood,” he added.
The team of scientists used a specially designed robot to apply force to the fingertips of 33 human volunteers. As the force was applied, nerve responses were measured using electrodes inserted into the volunteers’ peripheral nerves.
Neurons were sorted into three categories: fast-adapting type 1 (FA-1); slow adaptation type 1 (SA-1); and slow adapting type 2 (SA-2).
By varying the direction of the applied forces, the team was able to observe the effects of earlier forces on subsequent neural responses. Shuffling the stimuli led to a large increase in the variability of neuronal firing rates, particularly in SA-2 neurons, which sense forces in deeper tissues.
The research team found that this effect was related to the viscoelastic memory of the fingertip. They concluded that as these groups of tactile neurons transmit information to the brain, they carry with them the memory of past stimuli.