Electrical cortical activity associated with joint torque direction in the human arm

The objective of this study is to determine whether electrical brain activity differs for static joint torques generated in the elbow flexion/extension and shoulder abduction/adduction directions in humans. Electrical brain activity was quantified using a technique that incorporates a realistic, subject-specific electromagnetic head model to create a three-dimensional spatial resultant vector representation of the cortical region of activation. The findings demonstrate that generation of torque in each of the four directions produced significantly different locations of centers of cortical activation. These differences in location were maintained from preparatory to the early execution phases of the task. The organization of the centers of cortical activity during the generation of elbow/shoulder torques resulted in centers associated with the generation of elbow torques that were more lateral than centers accompanying shoulder torques in all five subjects tested. The authors conclude that electrical brain activity is spatially organized during the generation of joint torques in opposing directions at the elbow and shoulder joints. In addition, the results indicate that the center of the electrical brain activity associated with these static tasks is localized over the primary motor cortex as opposed to secondary sensorimotor cortices.