Human motor cortex oxygenation during exhaustive pinching task.

There are few observations of the activity of the bilateral motor cortex during prolonged exhaustive motor tasks. Knowing how the motor cortex modulates muscle fatigue or how information about fatigue affects motor cortex activities in healthy humans may help explain why fatigue is so prevalent in patients with neurological disorders. The purpose of the present study was to investigate the time course of oxygenation of the bilateral motor cortex during an exhaustive pinching task. Eight healthy, right-handed subjects participated in the study. Near-infrared spectroscopy over the bilateral motor cortex was used to measure the activity throughout the pinching task. Subjects performed a sustained 50-60% of maximal voluntary contraction until voluntary exhaustion was reached. After the start of the motor task, the contralateral motor cortex oxygenation increased significantly compared with the resting value (P<0.05). However, with the passage of time, it decreased significantly compared with the resting value (P<0.05). In addition, ipsilateral motor cortex oxygenation decreased significantly at voluntary exhaustion compared with the resting value (P<0.05). These results suggest an interaction between the bilateral motor cortices during motor tasks.