Network analysis of motor system connectivity in Parkinson's disease: Modulation of thalamocortical interactions after pallidotomy

Abstract

Abstract Structural equation modeling was used to examine functional interactions between cortical and subcortical motor areas in Parkinson's disease patients and normal subjects. Neuronal activity was defined by positron emission tomography (PET) imaging of regional cerebral blood flow ( r CBF) during performance of movement and control tasks. Patients were scanned before and 8‐12 weeks after stereotactic unilateral left posterovental globus pallidotomy. Pallidotomy attenuates basal ganglion inhibition of thalamocortical neurons involved in motor control and reduces the severity of bradykinesia in Parkinson's disease patients. It was hypothesized that with surgery there would be a similar alteration in thalamocortical interactions as measured with PET r CBF. A path analysis model of cortical and basal ganglia circuitry (defined by anatomic and electrophysiologic connectivity) was used to estimate unidirectional path coefficients describing the magnitude of region to region interactions. The resultant interactions defined a composite task‐and disease‐specific functional network of connectivity. After pallidotomy, there were significant reductions in the strength of interactions between the globus pallidus projection to thalamus, and the thalamus, projection to mesial frontal motor areas, consistent with the presumed physiologic interactions of these areas. This modeling approach can identify regional interactions that are not always apparent in categorical comparisons of inmaging data. ©1994 Wiley‐Liss, Inc.