The brain extends the body’s perception to the tools that we hold in our hands

Thursday, 2 January 2020

Tactile sensations, like a body part. This is what the brain perceives when it is holding an instrument that is externally stimulated,  according to the Somatosensory cortex efficiently processes touch located beyond the body study, published in Current Biology (DOI https://doi.org/10.1016/j.cub.2019.10.043).

Sixteen people held a rod in their hands that was subjected to external impacts and all the participants managed to locate the impact with almost perfect precision, as if it was their arm that had been touched. At the same time, the researchers, using electroencephalography (EEG), discovered that the position of the impact on the tool was decoded through the neural dynamics of the primary somatosensory cortex and the posterior parietal regions. These are the same areas that are activated when there is direct contact with the body.

The study, conducted by an international research team with the participation of the University of Milano-Bicocca’s Department of Psychology, showed that our brain applies the body’s tactile perception to an object, like an extension of the body.

The experiment opens up new avenues for the creation of increasingly precise prostheses that can adapt to the body. It has been demonstrated that even a person with no proprioceptive sensitivity in one arm manages to recognize the exact position of the impacts on the rod, confirming that impacts on the tool are only coded through touch.

“These results,” commented Nadia Bolognini, professor of Psychobiology and Physiological Psychology at Milano-Bicocca and co-author of the study, “suggest that it will be possible, in the not too distant future, to design increasingly less invasive and high-performance neurostheses, generating tactile signals in them which provide optimal responses when in contact with objects. This could be achieved by exploiting the mechanism identified in our study, which will allow the patient to locate tactile stimuli on a prosthesis in a natural way and thus facilitate the use of the prosthesis as if it were a real extended sensory organ.”