Experimental traumatic brain injury results in long-term recovery of functional responsiveness in sensory cortex but persisting structural changes and sensorimotor, cognitive, and emotional deficits

Traumatic brain injury (TBI) is a leading cause of death worldwide. In recent studies we have shown that experimental TBI caused an immediate (24 hr post) suppression of neuronal processing, especially in supragranular cortical layers. We now examine the long-term effects of experimental TBI on the sensory cortex, and how these changes may contribute to a range of TBI morbidities. Adult male Sprague Dawley rats received either a moderate lateral fluid percussion injury (n=14) or a sham surgery (n=12) and 12 weeks recovery before behavioural assessment, magnetic resonance imaging (MRI), and electrophysiological recordings from the barrel cortex. The TBI rats demonstrated sensorimotor deficits, cognitive impairments, and anxiety-like behaviour, and this was associated with significant atrophy of the barrel cortex and other brain structures. Extracellular recordings from ipsilateral barrel cortex revealed normal neuronal responsiveness and diffusion tensor MRI showed increased fractional anisotropy, axial diffusivity, and tract density within this region. These findings suggest that the long-term recovery of neuronal responsiveness is due to structural reorganisation within this region. Therefore it is likely that long-term structural and functional changes within sensory cortex post-TBI may allow for recovery of neuronal responsiveness, but that this recovery does not remediate all behavioural deficits.