Abstract
Transection of the direct cortico-motoneuronal (CM) pathway at the mid-cervical segment of the spinal cord in the macaque monkey results in a transient impairment of finger movements. Finger dexterity recovers within a week to a few months. Combination of brain imaging with positron emission tomography (PET) and reversible pharmacological inactivation of motor cortical regions with focal injection of muscimol showed that the recovery involves the bilateral primary motor cortex during the early recovery stage, and more extensive regions of the contralesional primary motor cortex and bilateral premotor cortex during the late recovery stage. These changes in the activation pattern of frontal motor related areas represent an adaptive strategy for functional compensation after spinal-cord injury. Furthermore, we recorded the focal field potentials in the motor cortices and EMG activities of hand/arm muscles in 2 monkeys. Cortico-muscular coherence at beta band (peak at 17Hz), which was observed in one of the monkeys disappeared and never recovered even after the functional recovery (3 months postoperatively). On the other hand, musculo-muscular at gamma band (peak at around 30 Hz), which was never observed preoperatively, became evident and prevailed widely among the hand/arm muscles and increased as the recovery progresses. These results suggest that some unknown low level common oscillator takes over the function to compensate for the dexterous finger movements after the lesion of the direct cortico-motoneuronal pathway. [J Physiol Sci. 2008;58 Suppl:S23]
