Chapter 26 Extensive cortical reorganization following sciatic nerve injury in adult rats versus restricted reorganization after neonatal injury: implications for spatial and temporal limits on somatosensory plasticity

Publisher Summary The major finding is that following peripheral deafferentation, cortical neurons, which have lost their major sensory inputs, switch their response patterns to become activated by adjacent peripheral inputs. A complete understanding of mechanisms underlying this reorganization requires investigations of the myriad changes in synaptic and intracellular signalling pathways that follow peripheral injury, and numerous studies have begun to address neurochemical responses of the cortical and thalamic somatosensory system to injury. The expansion of the saphenous representation in rat S-I cortex following sciatic nerve injury, examined at different times after injury and following injury at different developmental stages, has contributed to the beginnings of a comprehensive view of spatial and temporal patterns of cortical reorganization. In the first few days or weeks after deafferentation in adult animals, cortical reorganization may be spatially constrained to convergence zones between the central representations of peripheral nerves. To characterize the neurochemical consequences or mechanisms of cortical reorganization, it is necessary to consider possible differences between early versus late changes. Time dependent changes in neurotransmitters and their receptors have been described following peripheral injury.