Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2017 Sep 6:16:575-585.
doi: 10.1016/j.nicl.2017.09.004. eCollection 2017.

Distinct alterations in Parkinson's medication-state and disease-state connectivity

Affiliations

Distinct alterations in Parkinson's medication-state and disease-state connectivity

Bernard Ng et al. Neuroimage Clin. .

Abstract

Altered brain connectivity has been described in people with Parkinson's disease and in response to dopaminergic medications. However, it is unclear whether dopaminergic medications primarily 'normalize' disease related connectivity changes or if they induce unique alterations in brain connectivity. Further, it is unclear how these disease- and medication-associated changes in brain connectivity relate differently to specific motor manifestations of disease, such as bradykinesia/rigidity and tremor. In this study, we applied a novel covariance projection approach in combination with a bootstrapped permutation test to resting state functional MRI data from 57 Parkinson's disease and 20 healthy control participants to determine the Parkinson's medication-state and disease-state connectivity changes associated with different motor manifestations of disease. First, we identified brain connections that best classified Parkinson's disease ON versus OFF dopamine and Parkinson's disease versus healthy controls, achieving 96.9 ± 5.9% and 72.7 ± 12.4% classification accuracy, respectively. Second, we investigated the connections that significantly contribute to the classifications. We found that the connections greater in Parkinson's disease OFF compared to ON dopamine are primarily between motor (cerebellum and putamen) and posterior cortical regions, such as the posterior cingulate cortex. By contrast, connections that are greater in ON compared to OFF dopamine are between the right and left medial prefrontal cortex. We also identified the connections that are greater in healthy control compared to Parkinson's disease and found the most significant connections are associated with primary motor regions, such as the striatum and the supplementary motor area. Notably, these are different connections than those identified in Parkinson's disease OFF compared to ON. Third, we determined which of the Parkinson's medication-state and disease-state connections are associated with the severity of different motor symptoms. We found two connections correlate with both bradykinesia/rigidity severity and tremor severity, whereas four connections correlate with only bradykinesia/rigidity severity, and five connections correlate with only tremor severity. Connections that correlate with only tremor severity are anchored by the cerebellum and the supplemental motor area, but only those connections that include the supplemental motor area predict dopaminergic improvement in tremor. Our results suggest that dopaminergic medications do not simply 'normalize' abnormal brain connectivity associated with Parkinson's disease, but rather dopamine drives distinct connectivity changes, only some of which are associated with improved motor symptoms. In addition, the dissociation between of connections related to severity of bradykinesia/rigidity versus tremor highlights the distinct abnormalities in brain circuitry underlying these specific motor symptoms.

Keywords: Classification; Dopamine; FDR, false discovery rate; Functional magnetic resonance imaging; HC, healthy control; MDS-UPDRS, Movement Disorders Society-Unified Parkinson's disease Rating Scale; OAS, Oracle Approximating Shrinkage; PCC, posterior cingulate cortex; Parkinson's disease; ROI, region of interest; Riemannian geometry; SMA, supplementary motor area; fMRI, functional MRI.

PubMed Disclaimer

Figures

Fig. 1
Fig. 1
Significant connections between Parkinson's disease OFF versus ON dopaminergic medication. Circles represent the centroid for each region of interest. Red lines represent Parkinson's disease ON connectivity greater than OFF, blue lines represent Parkinson's disease ON connectivity less than OFF. L = left, R = right, Cau = caudate, Cer = cerebellum, Inf Temp = interior temporal lobe, MPFC = medial prefrontal cortex, PCC = posterior cingulated cortex, Put = putamen, and SMA = supplementary motor area.(For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 2
Fig. 2
Significant connections between Parkinson's disease OFF medication versus healthy controls. Circles represent the centroid for each region of interest. Connectivity in healthy controls was greater than Parkinson's disease OFF medication for all significant connections. L = left, R = right, Amy = amydala, MPFC = medial prefrontal cortex, Occ Pole = occipital pole, Put = putamen, Pal = pallidum, SMA = supplementary motor area, Sup Front = superior frontal gyrus, and Supramarg = supramarginal gyrus.
Fig. 3
Fig. 3
Relationship between SMA connectivity and Tremor severity. Partial Spearman's correlation (adjusted for gender and age). (A, B, C) Show the correlation between OFF medication projected connectivity and OFF Tremor whereas (D, E, F) show the correlation between relative medication-induced differences in projected connectivity, i.e. dCOff-dCOn, and dopaminergic improvement (OFF minus ON) in Tremor Subscore.
Fig. 4
Fig. 4
Relationship between Putamen connectivity and Bradykinesia/Rigidity severity. Partial Spearman's correlation (adjusted for gender and age). (A) Shows the correlation between OFF medication projected connectivity and OFF Bradykinesia/Rigidity whereas (B) shows the correlation between relative medication-induced differences in projected connectivity, i.e. dCOff-dCOn, and dopaminergic improvement (OFF minus ON) in Bradykinesia/Rigidity Subscore.

Similar articles

Cited by

References

    1. Agosta F., Caso F., Stankovic I., Inuggi A., Petrovic I., Svetel M. Cortico-striatal-thalamic network functional connectivity in hemiparkinsonism. Neurobiol. Aging. 2014;35(11):2592–2602. - PubMed
    1. Alberico S.L., Cassell M.D., Narayanan N.S. The vulnerable ventral tegmental area in Parkinson's disease. Basal Ganglia. 2015;5(2–3):51–55. - PMC - PubMed
    1. Argyelan M., Carbon M., Ghilardi M.F., Feigin A., Mattis P., Tang C. Dopaminergic suppression of brain deactivation responses during sequence learning. J. Neurosci. 2008;28(42):10687–10695. - PMC - PubMed
    1. Baudrexel S., Witte T., Seifried C., von Wegner F., Beissner F., Klein J.C. Resting state fMRI reveals increased subthalamic nucleus-motor cortex connectivity in Parkinson's disease. NeuroImage. 2011;55(4):1728–1738. - PubMed
    1. Behzadi Y., Restom K., Liau J., Liu T.T. A component based noise correction method (CompCor) for BOLD and perfusion based fMRI. NeuroImage. 2007;37(1):90–101. - PMC - PubMed