Plasticity in the brain is very extensive due to the brain’s parallel architecture and synaptic reorganization capabilities.   Because neuronal populations are typically in stable low energy minimums, it is limited under normal circumstances. This can be challenged, however, under extreme conditions. Brain stimulation is one such example.  By inhibiting active areas while rehabilitating others, electrical stimulation induces state changes in the neuronal networks.

With the objective to achieve more aggressive resection of brain tumors affecting eloquent areas, we subjected a group of 5 patients to prehabilitation.  This was achieved by progressively inhibiting cortical activity with high frequency stimulation via implanted subdural electrodes while the patients performed intensive exercise of affected functions over an average of 30 days. Functional MR showed the reorganization of cortical activity away from the stimulated area, with adjacent or even contralateral areas activated instead of the original ones. This allowed us to perform a more extended resection of the tumors without compromising the eloquent functions.

This procedure can be applied to additional pathologies affecting eloquent areas as well, such as epileptic foci or arteriovenous malformations. Importantly, the concept of associating cortical stimulation with rehabilitation has next level applications, for example to the recovery of lost functions after brain injury. The possibility to enhance weakened neuronal activity has been shown by pairing cortical stimulation with external physical rehabilitation with brain-machine interfaces in patients with motor deficit due to stroke. Possibilities of enhancement of plasticity by cortical stimulation are wide, although they may be limited by the existing neural networks supported by the white matter interconnections.