Motor urgency is mediated by the contralateral cerebellum in Parkinson's disease.
BACKGROUND
In patients with Parkinson's disease (PD), motor performance may be dramatically improved in urgent and stressful situations.


OBJECTIVE
The aim of this PET H(2)(15)O study was to determine the changes in brain activation pattern related to this unconscious increase in motor speed observed in the context of urgency in patients with PD.


METHODS
Eight right-handed patients with PD, who had been off medication for at least 12 hours, without tremor, were enrolled. A reaching task with the right hand was performed under three conditions: self-initiated (SI), externally cued (EC) and externally cued-urgent (ECu).


RESULTS
(1) Self-initiated movements (SI-EC) revealed activations in the prefrontal cortex bilaterally, the right lateral premotor cortex, anterior cingulate cortex and cerebellum, and the left primary motor cortex and thalamus; (2) Externally driven responses (EC-SI) did not involve any statistically detectable activation; (3) Urgent situations (ECu-EC) engaged the left cerebellum. Compared with a control group previously studied, the cerebellar activation was greater in patients with PD.


CONCLUSIONS
This study demonstrates that the increase in movement speed in urgent situations in patients with PD is associated with the recruitment of the left (contralateral) cerebellum. This structure is a key node of the accessory motor circuitry typically recruited by patients with PD to compensate for basal ganglia dysfunction and by healthy subjects to increase movement velocity in urgent motor contexts.
Ballanger
B
B
Center of Cognitive Neuroscience, CNRS UMR 5229, Bron, France.
Baraduc
P
P
Broussolle
E
E
Le Bars
D
D
Desmurget
M
M
Thobois
S
S
D000368:Aged; D002531:Cerebellum / Q000098:blood supply / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005260:Female; D005625:Frontal Lobe / Q000098:blood supply / Q000000981:diagnostic imaging / Q000503:physiopathology; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000000981:diagnostic imaging / Q000503:physiopathology; D009069:Movement Disorders / Q000175:diagnosis / Q000209:etiology*; D010300:Parkinson Disease / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D049268:Positron-Emission Tomography; D011930:Reaction Time; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed