Study Reveals How the Brain Reorganizes Sensory Maps After Loss of Touch

A team of researchers from the Institute for Neurosciences (IN), a joint center of the Spanish National Research Council (CSIC) and Miguel Hernández University (UMH) in Elche, has discovered that the developing brain can reorganize its sensory maps when the sense of touch is affected. In a study published today in Nature Communications, the Development, Plasticity, and Reprogramming of Sensory Circuits laboratory, led by Guillermina López-Bendito, has demonstrated that the somatosensory cortex can modify its structure and functionality in response to the absence of sensory stimuli from birth. This finding provides new insights into neural plasticity and the brain's ability to adapt to structural changes.

The study, conducted in collaboration with researchers from the Friedrich Miescher Institute for Biomedical Research in Switzerland, was carried out using a mouse model born without its principal whiskers.

We focused on the sensory map of the mouse's face because, for these animals, the face is as crucial as hands are for humans."

Mar Aníbal-Martínez, first author of the study

The researchers observed that, in the absence of the principal whiskers, the brain region that normally processes this information almost completely disappears, while the area associated with the upper lip whiskers, smaller, more numerous, and with secondary roles in tactile processing, expands to occupy its territory. This process occurs only if sensory loss takes place before birth.

Using genetic and bioinformatics analysis techniques, the team discovered that the thalamic region that normally processes information from the upper lip whiskers adopts a genetic profile similar to that of the principal whiskers when these are missing, enabling cortical reorganization. The researchers also found that spontaneous activity in the thalamus is redistributed following the loss of the principal whiskers.

Beyond structural changes, the reorganization also has a functional impact. "We not only observed a change in the anatomy of the sensory maps, but the small upper lip whiskers acquired a function previously exclusive to the principal whiskers: the ability to discriminate textures", says Aníbal-Martínez. This finding was confirmed through behavioral experiments in adult mice that had lost their principal whiskers before birth. These mice were able to distinguish between rough and smooth surfaces using only their upper-lip whiskers.

Furthermore, this study demonstrates that the reorganization of sensory maps does not rely on neuronal activity in the thalamus but rather on changes in its genetic profile. "The thalamus has traditionally been regarded as a mere relay station between the periphery and the cortex, but our work shows that it plays an instructive role in organizing sensory maps", explains López-Bendito. Her laboratory has revealed that the thalamus not only transmits information but also serves as a sensory integration center where all senses, except smell, converge. This underscores its crucial role in brain plasticity and the reorganization of tactile information.

These findings could provide a better understanding of how the brain of a person born without a body part reorganizes its sensory functions. "If a baby is born without a hand, their brain likely reconfigures tactile areas in a similar way", adds López-Bendito. "This not only helps us understand neural plasticity but also brings us closer to determining how we might intervene in the future to improve rehabilitation in cases of congenital malformations or early sensory loss".

This work was supported by grants from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (ERC Advanced Grant SPONTSENSE), the European Regional Development Fund (ERDF), the Spaniah State Research Agency – Ministry of Science, Innovation, and Universities, the Severo Ochoa Program for Excellence Centers of the Institute for Neurosciences CSIC-UMH, the PROMETEO program of the Generalitat Valenciana, the Swiss National Science Foundation (SNSF), and the Novartis Research Foundation.