Poster Sessions

IMAG -3

Cecile Gallea

C. Gallea, V. Voon, E. Houdayer, M. Hallett

Brain connectivity during dual motor tasks involving coupled or independent finger control: an fMRI study.

Background: The performance of two motor tasks at the same time depends on the task coordination requirements. One may experience more difficulty in expressing one or both of the tasks when they are independent than when the two tasks are identical. Since the abilities to perform dual tasks and independent movements are impaired in Parkinson Disease (PD) and Dystonia, to study the brain functioning during such tasks would help us to better understand the pathophysiology of those motor disorders. Objective: We studied brain connectivity changes depending on the linkage between two finger movements simultaneously performed. First, we analyzed the cortical network involved in simultaneous control comparing dual tasks versus two single tasks. Second, we analyzed the cortical coupling in this network depending on the coordination requirements of the dual tasks. Methods: 20 healthy volunteers performed a visuomotor task. The index finger controlled a cursor position to track a curve on the upper part of the screen while the middle finger controlled another cursor to track a curve at the bottom. Five different conditions (duration: 20s, followed by 12s rest) were recorded: (i) index finger alone; (ii) middle finger alone; (iii) coupled tracking of two identical curves, (iv) opposite tracking of two mirror curves; (v) independent tracking of two different curves. BOLD (Blood Oxygenation Level Dependent) signal was recorded using fMRI. Cortical activation and connectivity maps were calculated using SPM2 software. Results: Brain activation maps showed that BOLD signal increased with simultaneous control and with coordination requirements in bilateral parietal, premotor and supplementary motor areas. Connectivity between parietal, premotor cortices and superior frontal gyrus increased during coupled control compared to single tasks. During independent control versus coupled control, the cortical coupling (1) is more intense between primary motor, premotor and parietal cortices; (2) additionally engages the right cerebellum and bilateral basal ganglia. Conclusion: Bilateral cortical coupling in the sensorimotor system is more important when two simultaneous tasks have to be independently controlled. Abnormal connectivity patterns in basal ganglia (known to be impaired in PD and Dystonia) may partly explain inabilities to perform individuated finger movements. Complementary information about the timing of the brain processes will enhance our findings.