The brain activation on upper extremity motor control tasks in different forces levels.

Motor control is a critical process for muscle contraction initiated by nerve impulses governed by the motor cortex, which is vital for performing activities of daily living. The purpose of this study is to investigate brain activation in upper extremity motor control tasks in regulating the pushing force. Eighteen healthy young adults were asked to perform upper extremity motor control tasks, and recorded the hemodynamic signals using Functional Near-Infrared Spectroscopy and robotic arms. Two types of movement-static and dynamic-and three different task difficulties based on different force levels were used as force-regulating upper extremity motor control tasks. The hemodynamic response was collected in the primary motor cortex (M1), premotor cortex (PMC), supplementary motor area (SMA), and prefrontal cortex (PFC). The results showed a decrease in HbO for PFC was greater in the static relative to dynamic movement. Moreover, contralateral (c) M1, ipsilateral (i) PFC, and PMC have a significant increment in HbO mean compared to task difficulty. These findings indicate that the upper-extremity force and movement rely on separate cortical circuits: brain activation increases with difficulty in the cM1, PMC, and iPFC, whereas only the PFC distinguishes static from dynamic movement.