Overlapping and distinct neural metabolic patterns related to impulsivity and hypomania in Parkinson's disease.

Impulsivity and hypomania are common non-motor features in Parkinson's disease (PD). The aim of this study was to find the overlapping and distinct neural correlates of these symptoms in PD. Symptoms of impulsivity and hypomania were assessed in 24 PD patients using the Barratt Impulsiveness Scale (BIS-11) and Self-Report Manic Inventory (SRMI), respectively. In addition, fluorodeoxyglucose positron emission tomography (FDG-PET) imaging for each individual was performed. We conducted two separate multiple regression analyses for BIS-11 and SRMI scores with FDG-PET data to identify the brain regions that are associated with both impulsivity and hypomania scores, as well as those exclusive to each symptom. Then, seed-based functional connectivity analyses on healthy subjects identified the areas connected to each of the exclusive regions and the overlapping region, used as seeds. We observed a positive association between BIS-11 and SRMI scores and neural metabolism only in the prefrontal areas. Conjunction analysis revealed an overlapping region in the middle frontal gyrus. Regions exclusive to impulsivity were found in the medial part of the right superior frontal gyrus and regions exclusive to hypomania were in the right superior frontal gyrus, right precentral gyrus and right paracentral lobule. Connectivity patterns of seeds exclusively related to impulsivity were different from those for hypomania in healthy brains. These results provide evidence of both overlapping and distinct regions linked with impulsivity and hypomania scores in PD. The exclusive regions for each characteristic are connected to specific intrinsic functional networks.

Behavioural and neuroimaging correlates of impaired self-awareness of hypo- and hyperkinesia in Parkinson's disease.

INTRODUCTION: Anosognosia or impaired self-awareness of motor symptoms (ISAm) has been rarely investigated in Parkinson's disease (PD). We here studied the relationship between ISAm during periods with and without dopaminergic medication (ON- and OFF-state), and clinical, neuropsychological, and neuroimaging data to further elucidate behavioural aspects and the neurobiological underpinnings of ISAm. METHODS: Thirty-one right-handed, non-demented, non-depressed PD patients were included. ISAm was evaluated using a recently developed scale that assesses awareness of dyskinesia, resting tremor, and bradykinesia. The test was applied during both ON- and OFF-states. Multiple correlation analyses between ISAm and behavioural data were conducted. In addition, imaging of glucose metabolism using 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) was performed to investigate the neural basis of ISAm. A multiple regression approach was applied to investigate metabolism alterations related to ISAm. RESULTS: In the OFF-state, higher ISAm was associated with left-sided disease onset, older age, and shorter disease duration. Concerning FDG-PET data, there was a significant negative correlation between higher OFF-state ISAm and decreased glucose metabolism in the right inferior frontal gyrus (IFG). In the ON-state, ISAm was not significantly correlated with clinical or behavioural data. However, there was a significant correlation between higher ISAm and an increased metabolism in the bilateral medial frontal gyrus, left IFG, right superior frontal gyrus and right precentral gyrus. CONCLUSION: The results support the role of the right hemisphere in awareness of motor symptoms in the OFF-state. In the ON-state, dopaminergic medication and dyskinesia influence ISAm and relate to metabolism changes in bilateral frontal regions.

Impulsivity is Associated with Increased Metabolism in the Fronto-Insular Network in Parkinson's Disease.

Various neuroimaging studies demonstrated that the fronto-insular network is implicated in impulsive behavior. We compared glucose metabolism (as a proxy measure of neural activity) among 24 patients with Parkinson's disease (PD) who presented with low or high levels of impulsivity based on the Barratt Impulsiveness Scale 11 (BIS) scores. Subjects underwent 18-fluorodeoxyglucose positron emission tomography (FDG-PET) and the voxel-wise group difference of FDG-metabolism was analyzed in Statistical Parametric Mapping (SPM8). Subsequently, we performed a partial correlation analysis between the FDG-metabolism and BIS scores, controlling for covariates (i.e., age, sex, severity of disease and levodopa equivalent daily doses). Voxel-wise group comparison revealed higher FDG-metabolism in the orbitofrontal cortex (OFC), anterior cingulate cortex (ACC), and right insula in patients with higher impulsivity scores. Moreover, there was a positive correlation between the FDG-metabolism and BIS scores. Our findings provide evidence that high impulsivity is associated with increased FDG-metabolism within the fronto-insular network in PD.