Using fMRI to Understand the Roles of Brain Areas for Fine Hand Movements

OBJECTIVE: The present study focuses on evaluating neural activation patterns underlying praxis movements in normal controls and in patients with ideomotor apraxia using event-related functional magnetic resonance imaging (fMRI). Ideomotor apraxia is a disorder affecting patients with stroke and a variety of other brain lesions. The disorder involves disturbed timing, sequence, and spatial organization of skilled movements, during the execution and probably also preparatory phases. As a consequence, patients suffer from incorrect temporal and spatial components to movements as evidenced during pantomime of transitive (object/tool related) and intransitive (independent of object/tool use) gestures. Thus far, damage to posterior parietal regions and parietofrontal circuits has been implicated in significantly contributing to this disorder. However, little is known about the mechanism of cortical reorganization following damage, notably during recovery process. We hypothesize that recruitment of parallel and contralateral motor pathways compensates for reduced communication within parietofrontal circuits which prevents accurate motor performance. STUDY POPULATION: We will study two groups of participants: one group of patients with ideomotor apraxia and one group of healthy subjects. DESIGN: We will measure fMRI activation on transitive and intransitive gestures in 10 patients with ideomotor apraxia during subacute and chronic stage compared to 25 normal controls. The design of the behavioral paradigm incorporates a distinct period of planning prior to each movement. OUTCOME MEASURES: The design of this study allows evaluating any differences in the planning and execution phases between patients and controls. Further analysis will examine patterns of functional connectivity between activated brain areas, notably their altered interactions in ideomotor apraxia. Of special interest is the putative engagement of perilesional or even remote brain areas in a neuronal network during attempted recovery from motor deficit. It is expected from the study that a better understanding of cortical plasticity compensating for motor deficits in ideomotor apraxia can be therapeutically exploited, notably in the rehabilitation process.