Somatotopy in Parkinson's Disease

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Purpose The current investigation aims to study the altered striatal plasticity in early stage PD versus healthy controls to delineate the functional reorganization of dopaminergic projections in PD neurodegeneration. Analysis will be initially restricted to early PD, when compensatory mechanisms ar...

Purpose The current investigation aims to study the altered striatal plasticity in early stage PD versus healthy controls to delineate the functional reorganization of dopaminergic projections in PD neurodegeneration. Analysis will be initially restricted to early PD, when compensatory mechanisms are likely compensating for deficits arising from dopamine deficiency. The use of hybrid PET-MRI imaging will allow for the simultaneous assessment of patterns of striatal activation and functional connectivity, as well as dopamine release induced by a variety of cognitive and motor tasks. In the future, depending upon the findings of this study, we will examine the effects of disease progression on segregation of striatal function. Altered plasticity is likely to contribute to clinical progression of disease and to disease and treatment related complications, thus this investigation may help advance the development of more effective PD treatment measures. This investigation is intended as a pilot study. We currently do not have data on which to base a power analysis for sample size, however based on our previous experience using a double or triple bolus [11C] raclopride techniques, a sample size of 10 individuals per study group is adequate to detect between-group differences in dopamine release using a single bolus technique. Previous investigations we will be referencing in our study have similarly relied on small sample sizes to obtain their data. We are specifically interested in tracking functional changes within the brain in early PD, as this is when compensatory mechanisms are still compensating for deficits arising from dopamine deficiency. Thus for the purposes of this investigation we would like to focus on early PD, with the potential to follow the PD cohort in a longitudinal fashion in future investigations, to assess progressive loss of segregation over time. Hypotheses In healthy subjects, there will be segregation of striatal activation as measured by cerebral blood flow determined by BOLD fMRI, as well as striatal dopamine release determined using simultaneous [11C]raclopride PET, according to body site (motor activation) and task type (motor vs. cognitive vs. reward) In patients with PD, this segregation will be lost in a progressive fashion, in which caudal and dorsal striatal activation and dopamine release are lost first, with these functions shifted to progressively more rostral and ventral regions of the striatum. Research Design This is a cross-sectional study on 20 subjects (10 healthy control, 10 PD), involving 2-3 visits per subject to the Pacific Parkinson's Research Centre in UBC, Vancouver, BC. Each study participant will undergo 4 separate scans, 2 scans per day.

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