Hughlings Jackson's theory of recovery.

John Hughlings Jackson proposed a mechanism of neurologic compensation based on his theory of cerebral localization. According to Hughlings Jackson, there are three levels of evolution of the nervous system. Each element of each level contains a complete representation of the next lower level. Each element of the middle and highest levels contain a representation of the entire body, weighted for a particular part of the body. If the nervous system is damaged so that an area heavily weighted for a particular part of the body is destroyed, less heavily weighted areas are immediately activated according to their weighting. This activation partially compensates for the function of the destroyed tissue. As time passes, the weighting of representation in the unaffected areas changes, amplifying the degree of recovery. Recent clinical studies and PET cerebral blood flow studies show that various ipsilateral and contralateral areas are activated in recovery. The activated areas reside in what Hughlings Jackson would call the middle and highest evolutionary levels. Modern clinical and neurophysiologic observations are therefore consistent with Hughlings Jackson's theory of compensation.