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Título: The motor system in healthy individuals and in stroke patients before and after rehabilitative therapy /
Autores: Chouinard, Philippe
Fecha: 2005
Publicador: McGill University - MCGILL
Fuente:
Tipo: Electronic Thesis or Dissertation
Tema: Biology, Neuroscience.
Health Sciences, Rehabilitation and Therapy.
Descripción: A number of brain regions have been implicated in the recovery process after stroke. Yet, we still do not understand how these brain regions may influence each other. To overcome this problem, I used a perturb-and-measure approach, by combining transcranial magnetic stimulation (TMS) and positron emission tomography (PET), to examine effective connectivity of the motor system in healthy individuals and stroke patients. This doctorate thesis encompasses three studies. Together, the three studies provide new knowledge about effective connectivity and the function of the primary motor (M1) and dorsal premotor (PMd) cortices, and insights into rehabilitation-mediated recovery.
The first two studies examined effective connectivity and function of M1 and PMd in healthy individuals. Study I examined effective connectivity of M1 and PMd. This was achieved by stimulating the two cortical areas with repetitive TMS and measuring changes in cerebral blood-flow in the entire brain with PET. The results confirmed a hierarchical organization of the motor system. Repetitive TMS applied over M1 modulated a network of brain regions confined to the cortical and subcortical motor system. In contrast, repetitive TMS applied over PMd modulated a neural network that included several regions in the parietal and prefrontal cortices. Study 2 examined the role of M1 and PMd in the anticipatory scaling of forces during object lifting. This was achieved outside of the PET scanner by stimulating the two cortical areas using the same stimulation as in Study 1 and examining subsequent disruptions in the subjects' ability to lift different weights. The results demonstrated that M1 scales forces based on information acquired during a previous lift and PMd scales forces based on arbitrary cues.
Study 3 examined changes in the effective connectivity of M1 in stroke patients with chronic motor deficits (>1-year post-stroke) who underwent Constraint-Induced Movement Therapy (CI Therapy) for the affected arm. Improvements on various motor tests were observed immediately after therapy and were still present in most tests one-month afterwards. TMS/PET sessions were conducted before and immediately after therapy. During these sessions, I applied one-second trains of subthreshold 10-Hz repetitive TMS over the probabilistic hand representation of the ipsilesional and contralesional M1s and varied the number of TMS trains delivered during each scan. The results demonstrated changes in the effective connectivity of the ipsilesional M1 with a number of motor regions in the brain including the contralesional M1, the non-primary motor areas in both hemispheres, and the basal ganglia in both hemispheres. I speculate that these results represent a rehabilitation-induced strengthening of a neural network necessary for the development of compensatory skills.
Idioma: en