Abstract
A novel empirical mode decomposition method was adopted to investigate the dissociative or interactive neural impact of depression and motor impairments in Parkinson’s disease (PD). Resting-state fMRI data of 59 PD subjects were first decomposed into characteristic frequency bands, and the main effects of motor severity and depression and their interaction on the energy of blood-oxygen-level-dependent signal oscillation in specific frequency bands were then evaluated. The results show that the severity of motor symptoms is negatively correlated with the energy in the frequency band of 0.10–0.25 Hz in the bilateral thalamus, but positively correlated with 0.01–0.027 Hz band energy in the bilateral postcentral gyrus. The severity of depression, on the other hand, is positively correlated with the energy of 0.10–0.25 Hz but negatively with 0.01–0.027 Hz in the bilateral subgenual gyrus. Notably, the interaction between motor and depressive symptoms is negatively correlated with the energy of 0.10–0.25 Hz in the substantia nigra, hippocampus, inferior orbitofrontal cortex, and temporoparietal junction, but positively correlated with 0.02–0.05 Hz in the same regions. These findings indicate unique associations of fMRI band signals with motor and depressive symptoms in PD in specific brain regions, which may underscore the neural impact of the comorbidity and the differentiation between the two PD-related disorders.
Highlights
In the substantia nigra, thalamus and striatum structure, depression is associated with problems in the limbic system and basal forebrain[6,7]
Hamilton Depression Rating Scale (HDRS) scores were significantly higher in patients with depressed Parkinson’s Disease (DPD) than those with non-depressed Parkinson’s Disease (NDPD)
We did not find a correlation between UPDRS and HDRS scores (r = − 0.1487, p = 0 .2611), which indicates a non-linear or non-additive relationship between motor and depressive symptoms
Summary
In the substantia nigra, thalamus and striatum structure, depression is associated with problems in the limbic system and basal forebrain[6,7]. Such defects have been found in similar brain regions in patients with major depression It remains unclear whether the functional changes are general hallmarks of depressive symptoms independent of the motor disorder, or specific to the comorbidity of depression and movement deficiency[8]. Multiple ongoing neural processes may co-exist in the same brain area, which are characterized by brain waves of different frequencies[15] These processes can be reflected by BOLD oscillations in different frequency bands[16] and may be related to assorted brain functions, such as motor controls and mood regulations. With respect to the objective of this investigation, little is known about the frequency bands of BOLD oscillations or the corresponding brain areas which are related to motor deficiency, depression, or the interaction of the two aspects at the baseline condition. The energy of BOLD oscillations contained in each frequency band (IMF) was estimated and its correlations with motor severity, depression, and the interaction between the two were evaluated with a multivariate linear regression model
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