FUNCTIONAL MAGNETIC-RESONANCE-IMAGING OF MOTOR, SENSORY, AND POSTERIOR PARIETAL CORTICAL AREAS DURING PERFORMANCE OF SEQUENTIAL TYPING MOVEMENTS

We investigated the activation of sensory and motor areas involved in the production of typing movements using functional magnetic resonance imaging (fMRI). Eleven experienced typists performed tasks, in which the spatial and temporal requirements as well as the number of digits involved were varied. These included a simple uni-digit repetitive tas k, a uni-digit sequential task, a dual-digit sequential task, a multi- digit sequential task, and typing text from memory. We found that the production of simple repetitive keypresses with the index finger prima rily involved the activation of contralateral primary motor cortex (M1 ), although a small activation of the supplementary motor area (SMA) a nd other regions was sometimes observed as well. The sequencing of key presses involved bilateral M1 and a stronger activation of the SMA and to a lesser extent the premotor area, cingulate gyrus, caudate, and l entiform nuclei. However, the activation of these areas did not exclus ively depend on the complexity of the movements, since they were often activated during more simple movements, such as alternating two keypr esses repeatedly. Somatosensory and parietal regions were also found t o be activated during typing sequences. The activation of parietal are as did not exclusively depend on the spatial requirements of the task, since similar activation was observed during movements within intra-p ersonal space (finger-thumb opposition) and may instead be related to the temporal requirements of the task. Our findings suggest that the a ssembly of well-learned, goal-directed finger movement sequences invol ves the SMA and other secondary motor areas as well as somatosensory a nd parietal areas.