Spatial and Functional Organization of the Somato-Cognitive Action Network During Cue and Execution of Motor Tasks.

Primary motor cortex has traditionally been conceptualized as a somatotopically organized structure, with discrete cortical regions corresponding to specific body parts. However, accumulating evidence suggests that motor cortex organization extends beyond simple effector-based representations to include higher-order functional systems supporting goal-directed behavior. Here, we examine the somato-cognitive action network (SCAN), a set of inter-effector cortical regions located between the classical hand, foot, and face representations of primary motor cortex that has been proposed to integrate cognitive control processes with motor function. Using a fMRI motor task paradigm that dissociates cue-related and execution-related processes, we investigated the functional role and spatial organization of SCAN in healthy adults. SCAN exhibited preferential activation during the cue phase, 3.4-fold greater than during movement, indicating a prominent role in action preparation rather than motor output. In contrast, classical effector-specific motor representations (active during hand, foot, or face movement) showed greater engagement during execution, consistent with their role in movement generation. Across these SCAN regions, activation increased systematically from dorsomedial regions (adjacent to leg representations) to ventrolateral regions (adjacent to face representations). This spatial gradient was accompanied by progressively greater dominance of preparatory SCAN activity relative to movement-related activity in the adjacent effector regions. These findings demonstrate that motor cortex organization includes a distinct integrative system that is temporally and spatially dissociable from effector-specific representations. These results support an integrate-isolate framework in which cognitive and motor processes are differentially expressed across the cortical landscape, providing new insight into the functional architecture of human motor control.