Brain activation during human finger extension and flexion movements

Corticospinal projections to the motor neuron pool of upper-limb extensor m uscles have been reported to differ from those of the flexor muscles in hum ans and other primates. The influence of this difference on the central ner vous system control for extension and flexion movements is unknown. Cortica l activation during thumb extension and flexion movements of eight human vo lunteers was measured using functional magnetic resonance imaging (fMRI), w hich detects signal changes caused by an alteration in the local blood oxyg enation level. Although the relative activity of the extensor and flexor mu scles of the thumb was similar, the brain volume activated during extension was substantially larger than that during flexion, These fMRI results were confirmed by measurements of EEG-derived movement-related cortical potenti al. Higher brain activity during thumb extension movement may be a result o f differential corticospinal, and possibly other pathway projections to the motoneuron pools of extensor and flexor muscles of upper the extremities, (C) 2000 Elsevier Science B.V. All rights reserved.