Random Noise Stimulation to Enhance Corticomotor Drive for Improved Hand Function

Cervical spinal cord injury (SCI) results in upper extremity (UE) functional impairments that can restrict independence, social participation, and overall quality of life. Evidence shows that short duration of non-invasive brain stimulation (NIBS) can strengthen the transmission of information through the spared corticospinal pathways and improve UE functional recovery in individuals with tetraplegia. Transcranial direct current stimulation (tDCS), which is a clinically accessible NIBS approach, has been used to modulate cortical plasticity and improve hand function. However, the high variability in the reported effects of tDCS raises questions about its clinical value and highlights the need to investigate more robust NIBS protocols. Transcranial random noise stimulation (tRNS) is a novel NIBS approach that produces more consistent facilitatory effects compared to tDCS. TRNS delivers a low alternating current with a continuously changing intensity over a wide frequency range. Further, tRNS has excellent tolerability and no risk of skin burns since it is a polarity independent stimulation approach. When tRNS is applied over the motor cortex, it increases cortical excitability in the hand representation area and enhances motor learning in healthy adults. Despite the potential promise of tRNS in increasing corticomotor drive for improved motor performance, its application in persons with SCI is novel. Therefore, in this study, the investigators propose to use tRNS to augment the therapeutic effects of functional task practice (FTP). Our aim is to compare the efficacy of a 3-day tRNS+FTP protocol on cortical excitability, UE motor, and sensory function to tDCS+FTP and to sham-stimulation+FTP in individuals with tetraplegia.