Reorganization of Functional Connectivity Patterns of Striatum and Default Mode Network in Parkinsons Disease with Impulse Control Disorders

Abstract

Impulse control disorders (ICD) have been reported to develop in patients with Parkinsons disease (PD) following dopamine-replacement therapy. In this study, we performed resting state fMRI to examine the spatial changes in the functional connectivity patterns of the striatum and posterior cingulate cortex in PD with ICD. Functional correlations of three striatal seed regions (caudate head, anterior putamen and posterior putamen) and posterior cingulate were calculated and compared across nine healthy controls (HC), ten PD patients with ICD (PDICD) and eight PD without ICD (PDC). The striatal regions were functionally disconnected in many cortical areas as a result of neurodegenerative process in PD, however, the functional connectivity with parahippocampal gyrus encompassing hippocampus and amygdala was enhanced in both PDC and PDICD, perhaps as a drug-induced plastic change in the relatively preserved mesolimbic system. The putaminal connectivity with the cerebellum was more depressed in PD patients displaying ICD than PDC, but more enhanced in the precentral and postcentral cortices, apparently as a compensatory plastic change for the functional deficits in cerebellum and basal ganglia. In PDICD, functional hyperconnectivity between the striatum and parahippocampal gyrus and insula, where are parts of a network implicated in impulse control and response inhibition also were noticeable. The abnormal functional changes in the network in PD patients may reinforce the development of ICD or may occur as a secondary change following the psychiatric process. The medication-related dysfunction of a striatal network involving the thalamus may also be involved in the emergence of ICD in PD. The integrity of default mode network (DMN) markedly depressed in several areas including inferior parietal lobule, precuneus and middle cingulate in PDC compared to HC. In contrast, the DMN connectivity elevated in hippocampus and precuneus, but perturbed in the middle cingulate in PDICD compared to HC. In PDC versus PDICD, PDICD displayed the DMN functional enhancements in inferior parietal lobule, cingulate and precuneus, apparently resulting from medication-complicated behavioral changes.