Successive bilateral frontal controlled cortical impact injuries show behavioral savings

Traumatic brain injuries (TBIs) affect millions of people each year. Research investigating repeated or serial damage in the form of lesions indicates that behavioral deficits are reduced in animals given sequential lesions separated by a sufficient period of recovery. In the lesion literature, this phenomenon is known as the serial lesion effect (SLE). Although the SLE phenomenon is established in the lesion literature, it has not been thoroughly investigated under current models of brain injury. In the current study, a controlled cortical impact of the bilateral frontal cortex was performed in either a single procedure or a serial procedure separated by two weeks. Rats were tested on the Morris water maze, bilateral tactile adhesive removal task, rotarod and Barnes maze task to determine behavioral deficits. Histology was performed to determine lesion size and astrocyte and microglial response. A serial lesion effect was demonstrated across a majority of the behavioral tasks. However, histological analyses did not suggest a clear mechanistic link to the behavioral phenomena. This is the first study to demonstrate the SLE in a model of TBI, suggesting that behavioral deficits may actually be reduced in repeated head injuries, given an adequate time window between injuries.

► The serial lesion effect can be demonstrated in a model of traumatic brain injury.
► Two sequential brain injuries reduce deficits; brain injury is not necessarily additive.
► The serial lesion effect cannot be tied conclusively back to the glial response.