Background: In Parkinson’s disease (PD) patients, motor performance may be dramatically improved in urgent and stressful situations. Objective: The aim of this PET H215O study was to determine the changes of brain activation pattern related to this unconscious motor speed up observed in the context of urgency in PD patients.
Methods: Eight right handed PD patients, 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, 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 to a control group previously studied the cerebellar activation was greater in PD patients.
Conclusions: This study demonstrates that the increase of movement speed in urgent situations in PD patients is associated with the recruitment of the left (contralateral) cerebellum. This structure is a key node of the accessory motor circuitry typically recruited by PD patients to compensate for basal ganglia dysfunction and by healthy subjects to increase movement velocity in urgent motor contexts.