Brain activity during visuomotor behavior triggered by arbitrary and spatially constrained cues: an fMRI study in humans

Rule-based behavior associating nonspatial visual stimuli with learned responses is called arbitrary visuomotor mapping, an ability that enriches behavioral repertoire. To better understand the underlying neural correlates, the present functional magnetic resonance imaging (fMRI) study explored brain activity during visually informed movement involving two different types of cues and two different effectors. After being trained on the tasks, six healthy subjects performed right or left finger tapping tasks according to either arbitrary cues or spatially constrained cues. An event-related fMRI experiment was conducted on a 3-T MRI. The image data were analyzed with statistical parametric mapping. With the aid of the probabilistic architectonic map in the stereotaxic space, we identified three types of task-related brain activity: cue-selective, effector-selective, and nonselective. The left ventrolateral prefrontal cortex and the rostral part of the right dorsal premotor cortex (PMd) exhibited cue-selective activity, which was greater during the arbitrary condition than the spatially constrained condition. The left ventral prefrontal activity may reflect retrieval of visuomotor association from memory in arbitrary context. The rostral part of the left PMd showed nonselective activity while the caudal part of the PMd on each side showed conspicuous effector-selective activity to the contralateral movement. These findings suggest functional demarcation of the PMd between its rostral and dorsal parts during visuomotor mapping.