The functional significance of cortical reorganization and the parallel development of CI therapy

Abstract

For the nineteenth and the better part of the twentieth centuries two correlative beliefs were strongly held by almost all neuroscientists and practitioners in the field of neurorehabilitation. The first was that after maturity the adult CNS was hardwired and fixed, and second that in the chronic phase after CNS injury no substantial recovery of function could take place no matter what intervention was employed. However, in the last part of the twentieth century evidence began to accumulate that neither belief was correct. First, in the 1960s and 1970s, in research with primates given a surgical abolition of somatic sensation from a single forelimb, which rendered the extremity useless, it was found that behavioral techniques could convert the limb into an extremity that could be used extensively. Beginning in the late 1980s, the techniques employed with deafferented monkeys were translated into a rehabilitation treatment, termed Constraint Induced Movement therapy or CI therapy, for substantially improving the motor deficit in humans of the upper and lower extremities in the chronic phase after stroke. CI therapy has been applied successfully to other types of damage to the CNS such as traumatic brain injury, cerebral palsy, multiple sclerosis, and spinal cord injury, and it has also been used to improve function in focal hand dystonia and for aphasia after stroke. As this work was proceeding, it was being shown during the 1980s and 1990s that sustained modulation of afferent input could alter the structure of the CNS and that this topographic reorganization could have relevance to the function of the individual. The alteration in these once fundamental beliefs has given rise to important recent developments in neuroscience and neurorehabilitation and holds promise for further increasing our understanding of CNS function and extending the boundaries of what is possible in neurorehabilitation.

Motor System Reorganization After Stroke: Stimulating and Training Toward Perfection

“…While it is not feasible to replicate our rodent behavioral manipulations in a similarly controlled fashion in humans, our findings are highly consistent with behavioral and neural phenomena of learned-nonuse suggested by Taub et al (178,179). Since experience with the weakness and ineptitude of the paretic side leads to reliance on the nonparetic limb, this reduces practice with the paretic limb, reducing its influence on neural reorganization.…”

Knee rotationplasty: motion of the body centre of mass during walking

“…Contrary to this expectation, both the stumps of amputees and the rotated limb of KRP patients invariably become hypotrophic: as suggested by Tesio et al (2014), this might represent an example of ‘learned-nonuse’ (Taub et al , 2014) involving the affected lower limb in case of unilateral impairments, whichever the cause (Tesio et al , 1998b). Consistently enough, in the same three KRP patients the rotated plantar flexors were found to be under-represented in the contralateral motor cortex in a study based on brain mapping through transcranial magnetic stimulation (Tesio et al , 2014).…”

Motor compensation and its effects on neural reorganization after stroke

“…This disuse has been proposed to result from ‘learned non-use’, whereby repeated experience with the weakness and ineptitude of stroke-impaired functions encourages their disuse 8 . This idea was originally based on observations in macaque monkeys with peripheral sensory deafferentation of one arm, which the monkeys continued to disuse even after its capacity to move returned 79 .…”

“…Humans use both hands together most of the time 7 , and the loss of the function of either hand requires major adjustments to our interactions with the physical world. A common response to this loss after stroke is to learn compensatory ways of relying on the better-functioning, non-paretic hand 8,9 . There are also compensatory changes in the coordination of movements of both hands and of the paretic forearm with the trunk, as explained below.…”

“…Another reason to attend to compensation is that it is both a mechanism for improved function and a contributor to persisting impairment after CNS injury 8,10,11 . There is currently much interest in the potential to optimize functional outcome after CNS damage by capitalizing on early endogenous mechanisms of neural repair and remodelling after stroke, which are sensitive to behavioural manipulation and could facilitate the efficacy of motor rehabilitation 12–15 .…”