Reveiw: Cortical reorganization after spinal cord injury: Always for good?

Neuroscience 283 (2014) 78–94

K. A. Moxon, A. Oliviero, J. Aguilar, and G. Foffani

http://dx.doi.org/10.1016/j.neuroscience.2014.06.056

This review paper gave me a vivid image of the plastic nature in brain function. The cortical map is not a static representation. It represents dynamic equilibrium of continuous interactions of the brain and the external world. Such fluidic nature of the brain is remarkable during the sensorimotor learning.  It becomes especially important when the brain goes through functional recovery after injury and rehabilitation. Upon spinal cord injury, a change in brain state occurs immediately to start cortical reorganization. 

   A complete thoracic spinal cord transection immediately changes the state of the brain, decreasing cortical spontaneous activity as evidenced by a slowing of the frequency of anesthesia-induced oscillations, while increases the cortical responses to stimuli delivered above the level of the lesion. The increased responses could be due to a change in the equilibrium between excitation and inhibition at cortical and subcortical levels.

   There is a species differences in the cortical reorganization. In human, the spinal lesion induces an enlargement of cortical sensorimotor areas representing preserved muscles above the level of lesion. Primates brain may be more flexible than rodents, in which spontaneous cortical reorganization is more limited.

   The authors discussed potential therapy that involves 5-HT and exercises. Activation of 5-HT receptors facilitates cortical reorganization by restructuring connections that could be relevant for behavioral recovery. Cortical reorganization can also be promoted by exercise therapy, which increases brain BDNF levels. This peptide and 5-HT together favors cortical reorganization and functional recovery after spinal cord injury.