Abstract
Although nigrostriatal changes are most commonly affiliated with Parkinson's disease, the role of the cerebellum in Parkinson's has become increasingly apparent. The present study used lobule-based cerebellar resting state functional connectivity to (1) compare cerebellar-whole brain and cerebellar-cerebellar connectivity in Parkinson's patients both ON and OFF L-DOPA medication and controls, and to (2) relate variations in cerebellar connectivity to behavioral performance. Results indicated that, when contrasted to the control group, Parkinson's patients OFF medication had increased levels of cerebellar-whole brain and cerebellar-cerebellar connectivity, whereas Parkinson's patients ON medication had decreased levels of cerebellar-whole brain and cerebellar-cerebellar connectivity. Moreover, analyses relating levels of cerebellar connectivity to behavioral measures demonstrated that, within each group, increased levels of connectivity were most often associated with improved cognitive and motor performance, but there were several instances where increased connectivity was related to poorer performance. Overall, the present study found medication-variant cerebellar connectivity in Parkinson's patients, further demonstrating cerebellar changes associated with Parkinson's disease and the moderating effects of medication.
Highlights
Parkinson’s disease is a neurodegenerative disorder characterized by both motor and cognitive impairments
One prior study has examined cerebellar resting state functional connectivity in Parkinson’s patients, but this study solely focused on connectivity from the dentate nucleus of the cerebellum and only tested Parkinson’s patients OFF medication (Liu et al, 2013)
Behavioral Results ON vs. OFF Generally, Parkinson’s patients had better behavioral performance when ON medication than when OFF medication. This behavioral difference was significant for the Grooved Pegboard completion time with the more affected hand, such that Parkinson’s patients took longer when OFF medication, [t(24) = 2.88, p = 0.008, d = 0.24]
Summary
Parkinson’s disease is a neurodegenerative disorder characterized by both motor and cognitive impairments. When compared to controls, Parkinson’s patients OFF dopaminergic medication have exhibited greater activity in the cerebellum while performing various upper limb movements (Jahanshahi et al, 1995; Catalan et al, 1999; Wu and Hallett, 2005, 2008; Cerasa et al, 2006; Yu et al, 2007; Wu et al, 2010). Greater activation of the ipsilateral cerebellar hemisphere in Parkinson’s patients OFF medication has been observed during a hand movement task, when compared to patients ON medication and controls (Rascol et al, 1997). Enhanced cerebellar activation was present during early motor learning in Parkinson’s patients ON medication as well, when behavioral performance was equivalent between patients and controls (Bédard and Sanes, 2009)
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