UCLA

After a lateralized traumatic brain injury (TBI), neural repair and regeneration in the area proximal to the injured region is known to be associated with recovery of some of the function lost to injury. However, there is a growing body of evidence, mostly from stroke research that distant, but networks which are both functionally and structurally connected to the injured cortical region are not only indirectly altered by injury, but may also be critically involved in the recovery process. One such region, called the contra-lesional cortex (CLCtx), is the uninjured, homotopic brain region mirrored on the opposite cerebral hemisphere. Here, we sought to determine how the cortical map is altered by injury and whether the CLCtx is causally involved in recovery of function after unilateral TBI. We used functional magnetic resonance imaging (fMRI) and in vivo electrophysiology to chart the changes in the functional map throughout recovery from experimental TBI in the rat. To determine if the CLCtx is involved in functional recovery, we tested function with and without temporary inactivation of the CLCtx at weekly for the first month after injury. The results of these experiments indicated that the functional map shifts to the CLCtx throughout the first four weeks after injury. At 4 weeks post-injury, silencing the CLCtx re-instated the injury deficit, indicating that the CLCtx was supporting functional recovery chronically. Surprisingly, silencing activity of the CLCtx at just one week post-injury resulted in a complete recovery of function, indicating that the CLCtx is impeding function of the affected forelimb. Therefore, with its causative role in recovery of function after TBI, the CLCtx might be an important target for future interventional strategies in TBI recovery.