The influence of time after stroke on brain activations during a motor task.

After stroke, the pattern of brain activation during performance of a motor task is related to outcome. Here, we compare this relationship in the early (10-14 days) and late (at least 3 months) phases after first-ever stroke. A negative linear relationship between task-related brain activation, as measured by functional magnetic resonance imaging, and outcome is seen in several identical primary and nonprimary motor regions that is independent of time after stroke. In other words, patients with poorer outcome scores recruit more widely within motor-related regions in both the early or late poststroke phase. However, in contralesional middle intraparietal sulcus, contralesional cerebellum, and ipsilesional rostral premotor cortex, this relationship is seen only in the early poststroke phase. Thus, patients with poorer outcome scores recruit these areas in only the early and not the late poststroke phase. These results suggest that there are differences in the cerebral implementation of action in patients with poor outcome that are dependent on the time since stroke. Thus, in those patients with the most to gain from rehabilitation, different therapeutic approaches may be required at different stages after stroke.