PHYSIOLOGICAL ANALYSIS OF VOLUNTARY MOVEMENT

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The goal of this project is to learn more about the control of movement in normal humans and in patients with voluntary movement disorders such as Parkinson's disease (PD), cerebellar ataxia, hemiplegia from stroke, and dystonia. We have been using EEG methods to explore timing of cortical activation in relation to voluntary movement. Additionally, spectral power and coherence analyses of EEG in a visuomotor integration task indicated that functionally meaningful, network-like coupling of distant brain areas (motor and visual cortex) occurs during visuomotor force tracking, but not during simultaneous but functionally unrelated motor output and visual input. In relation to cerebellar ataxia, we have evaluated the kinematics of straight planar arm movements in several directions. Findings reveal consistencies in abnormalities of force control. The results are also being incorporated into a model of cerebellar function. Using EEG and PET, we determined that the normal homuncular organization of the primary sensory cortex is degraded in patients with focal dystonia supporting the concept that sensory abnormalities play a pathogenetic role in dystonia. We have evaluated brain activity with EEG and PET during implicit and explicit learning of the serial reaction time task (SRTT). The SRTT was used to evaluate motor learning in patients with cerebellar dysfunction. Motor learning with classical conditioning of the blink reflex was studied in patients with Parkinson's disease and progressive supranuclear palsy. Patients with PD were normal suggesting that the basal ganglia do not play a major role in this type of learning. Patients with PSP were abnormal, likely due to cerebellar malfunction, but this abnormality will separate these patients from those with PD. We have studied the cutaneous withdrawal ("flexor") reflex and cutaneomuscular reflex in the upper extremity in normal subjects and characterized the stimulus necessary to evoke withdrawal reflexes, the pattern of muscle activation, habituation of the reflex and effects of contralateral cutaneous stimuli. We concluded that the underlying circuitry for this weak reflex bears similarity to that described in the leg. PET and EEG were used to evaluate how the brain processes somatosensory stimuli and sound stimuli in blind subjects. For both modalities, we found activation in visual areas indicating cross-modal plasticity. PET and EEG are being used to evaluate brain activity during movement in patients with stroke. A double-blind trial of buspirone for treatment of cerebellar ataxia has been carried out following up our previous open trial findings.