A main goal of rehabilitation strategies in humans with SCI is to strengthen transmission in spared neural networks. Although neuromodulatory strategies have targeted different sites within the central nervous system to restore motor function following SCI, the role of cortical targets remains poorly understood.
“I am excited to see that electrophysiology can be successfully used to guide interventions for recovery of function after spinal cord injury,” says Dr. Perez.
In this study, Drs. Perez, Jinyi Long, Ph.D., and Paolo Federico, Ph.D. used 180 pairs of noninvasive transcranial magnetic stimulation for 30 minutes over the hand representation of the primary motor cortex at an interstimulus interval mimicking the rhythmicity of descending late indirect (I) waves in corticospinal neurons (4.3 ms; late I-wave protocol) or at an interstimulus interval in-between I-waves (3.5 ms; control protocol) on separate days in a randomized order.
Late I-waves are thought to arise from trans-synaptic cortical inputs and have a crucial role in the recruitment of spinal motor neurons following SCI. The researchers found that the excitability of corticospinal projections to intrinsic finger muscles increased in SCI and uninjured participants after the late I-wave but not the control protocol for 30 to 60 minutes after the stimulation. Importantly, individuals with SCI were able to exert more force and electromyographic activity with finger muscles after the stimulation showing an enhanced ability to grasp small objects with their hands.
University of Miami Miller School of Medicine
Jinyi Long, Paolo Federico, Monica A. Perez.
A novel cortical target to enhance hand motor output in humans with spinal cord injury. Brain, 2017; 140 (6): 1619 DOI: 10.1093/brain/awx102