METABOLIC CORRELATES OF PALLIDAL NEURONAL-ACTIVITY IN PARKINSONS-DISEASE

We have used [F-18]fluorodeoxyglucose and PET to identify specific met abolic covariance patterns associated with Parkinson's disease and rel ated disorders previously. Nonetheless, the physiological correlates o f these abnormal patterns are unknown. In this study we used PET to me asure resting state glucose metabolism in 42 awake unmedicated Parkins on's disease patients prior to unilateral stereotaxic pallidotomy for relief of symptoms. Spontaneous single unit activity of the internal s egment of the globus pallidus (GPi) was recorded intraoperatively in t he same patients under identical conditions. The first 24 patients (Gr oup A) tt ere scanned on an intermediate resolution tomograph (full wi dth at half maximum, 8 mm); the subsequent 18 patients (Group B) were scanned on a higher resolution tomograph (full width half maximum, 4.2 mm). We found significant positive correlations between GPi firing ra tes and thalamic glucose metabolism in both patient groups (Group A: r = 0.41, P < 0.05; Group B: r = 0.69, P < 0.005). In Group B, pixel-ba sed analysis disclosed a significant focus of physiological-metabolic correlation involving the ventral thalamus and the GPi (statistical pa rametric map: P < 0.05, corrected). Regional covariance analysis demon strated that internal pallidal neuronal activity correlated significan tly (r = 0.65, P < 0.005) with the expression of a unique network char acterized by covarying pallidothalamic and brainstem metabolic activit y Our findings suggest that the variability in pallidal neuronal firin g rates in Parkinson's disease patients is associated with individual differences in the metabolic activity of efferent projection systems.