The capacity of the adult human nervous system to alter the strength of connections between neurons and between networks of neurons is an exciting area of research providing novel insights into the mechanisms involved in learning, memory and recovery following brain damage. In recent years, it has become clear that both afferent input into the motor cortex and the learning of a new motor task can drive cortical reorganisation. This thesis is concerned with the functional significance of this plasticity, in both normal subjects and stroke patients, and with the question of whether stimulation - induced plasticity can lead to improved fine motor performance. My initial experiments were conducted to determine the optimal method of analysing responses to transcranial magnetic stimulation ( TMS ), and to investigate aspects of motor performance as the hand performs a precision task to grasp and lift an object. Studies on normal subjects showed that there is little difference between the dominant and non - dominant hands performing this task, but the type of grip used influences grip - force control. An investigation of stroke patients performing this task demonstrated that certain parameters were sensitive to differences between the affected and unaffected hands and these parameters were highly correlated with stroke - specific functional outcome measures. The induction of plastic change in the human motor cortex can be induced by repetition of movements, performing a complex motor task or stimulation of the peripheral afferents and / or the motor cortex itself. I observed that the application of so - called " associative stimulation " to two hand muscles in normal subjects increased the excitability of the corticospinal projection to those muscles, and improved performance times on a subsequent motor task to a greater extent than subjects receiving a control intervention. I then applied associative stimulation to the affected hand of stroke patients in conjunction with rehabilitation, which improved their ability to perform the dextrous grip - lift task. This is the first study to show that this method of inducing motor cortical plasticity can also lead to functional improvements in stroke patients. These studies confirm that using afferent stimulation to drive cortical reorganisation is associated with improved function and fine motor performance in both normal subjects and stroke patients. / Thesis (Ph.D.)--School of Molecular and Biomedical Science, 2006.

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Social Work and Social Administration / Doctoral / Doctor of Philosophy

Not available / text

The leading cause of long-term disability among adults in industrialized countries is stroke. Exploration of the brain mechanisms involved during recovery from stroke is likely to yield information that can be used to promote better functional outcome. After focal motor cortical infarcts, reorganization of movement representations in the remaining motor cortex has been linked to both spontaneous recovery and recovery induced by rehabilitative training. However, the mechanisms and nature of cortical reorganization remain poorly understood. The central hypothesis of these dissertation studies is that synaptogenesis and structural reorganization in the cortex near the lesion are linked to spontaneous partial recovery and the beneficial effects of motor rehabilitative training after stroke-like injury. This was tested in a rat model of focal cortical ischemia by both behavioral and neuroanatomical measures in perilesion cortex. In separate studies, it was found that motor rehabilitative training on a skilled reaching task using the impaired forelimb after a unilateral ischemic lesion improved forelimb functional outcome and facilitated synaptogenesis in perilesion cortex. In addition, this improved functional recovery was disrupted by focal protein synthesis inhibition in perilesion cortex, suggesting the structural plasticity in this area plays an important role in regained function. Finally, it was also hypothesized that a therapy that enhances the efficacy of motor rehabilitation also enhances synaptic structural plasticity in perilesion cortex. Cortical electrical stimulation (CS) during motor rehabilitation has previously been shown to improve the efficacy of rehabilitation. Increased density of axodendritic synapses in perilesion cortex was found in rats that received cortical electrical stimulation of perilesion cortex during rehabilitation compared to rehabilitation alone, and the synaptic density was positively correlated with post-rehabilitation reaching performance. These findings suggest that CS-induced functional improvements may be mediated by synaptic structural plasticity in stimulated cortex. Together these studies indicate that, after a cortical lesion in rats, motor rehabilitation alone or in conjunction with other efficacious therapies can greatly enhance synaptic structural plasticity in perilesion cortex. Furthermore, these studies suggest that rehabilitation induced improvements in functional outcome are dependent upon the structural and functional integrity of the reorganized perilesion cortex.

published_or_final_version / Social Work / Master / Master of Social Sciences

published_or_final_version / Psychology / Master / Master of Philosophy

No description available.

No description available.

The present study investigated the extent to which right and left hemisphere stroke patients, within an acute care rehabilitation unit, differ in neuropsychological symptomatology as reported on a self-report instrument.The subjects were 90 patients admitted to an acute care rehabilitation unit within a midwestern hospital. Two groups of 30 were obtained on the basis of stroke location, either right or left hemisphere. In addition, a group of 30 orthopedic patients were selected to serve as a comparison group.Data was collected using the Neuropsychological Symptom Inventory (Rattan, Dean & Rattan, 1989). A discriminant analysis revealed two discriminant functions which were used to classify group membership. Slightly more than 86% of both left hemisphere stroke patients and orthopedic patients were correctly classified. However, only 46% of right hemisphere stroke patients were accurately predicted. The results clearly support the ability to differentiate the groups and suggest a homogeneous character of the left hemisphere stroke and orthopedic groups. The right hemisphere group appears heterogeneous in make-up. Further statistical analysis revealed no significant difference (a<.05) between stroke groups when examining a factor related to emotional/depression symptoms. However, when stroke patients were compared to orthopedic patients on this factor, a high degree of significance was revealed (p<.001).These results suggest that right hemisphere patients cannot be treated as if they make up a single disorder group within the rehabilitation setting. The use of a self-report measure may prove beneficial with this group is assessing the level of neuropsychological impairment and to make modifications in treatment planning. Additionally, the existence of depression within the stroke group suggest that rehabilitation should focus more on these reactions within the first few weeks post-stroke. / Department of Educational Psychology