In this study we analyze the brain signal phase components to understand patterns of interactions in the motor cortex. Nonhuman primate motor-cortical activity was recorded with electrocorticography (ECoG) arrays along with intramuscular electromyography (EMG) during natural reaching and grasping hand movements. This study investigates phase relationships between each ECoG electrode pair to decode neural signal propagation. We propose a method to cluster recording channels that have similar phase characteristics and suggest a mapping of the signal pathway in motor cortex. This technique can facilitate further studies on corticomuscular coherence and development of effective prosthetics for motor impairment in patients.