Modeling brain reorganization after hemispherectomy

Brain reorganization after hemispherectomy (i.e. the removal of a whole hemisphere) is perhaps the most remarkable example of large-scale brain plasticity. Most often patients survive and recover their skills. Functional traits located in the lost side (e.g. language areas) can sometimes be completely reassembled in the remaining hemisphere, which seamlessly takes on the additional processing burden. This demands drastic rearrangements, perhaps involving the readaptation of functionally and structurally diverse neural structures. We lack mathematical models of how this happens. We introduce a very simple model, based on self-organized maps, that provides a rationale for the clinical aftermath of the intervention, putative windows for recovery, and the origins and nature of observed thresholds for irreversible function loss. The implications for brain symmetry and potential scenarios in simulated pathologies, including efficient suggested treatments, are outlined.