Engaging reticulospinal inputs to improve walking

Abstract Locomotor recovery is one of the most important goals of individuals with spinal cord injury (SCI). Ambulatory

deficits severely impact daily functions resulting in lower quality of life for people living with paralysis due to SCI. Although studies have shown that locomotor training improves locomotor function in people with chronic SCI, the benefits remain limited. Our overall hypothesis is that we can engage additional descending motor pathways,

such as the reticulospinal tract (RST), to improve locomotor function in humans with chronic incomplete SCI. The goals of this proposal are: (1) Examine the contribution of the RST to lower limb muscles during locomotion, and (2) to combine non-invasive paired RST activation and electrical muscle stimulation with treadmill training

to improve motor output in individuals with chronic incomplete SCI. In Aim 1, we propose to measure the effects of a loud auditory stimulus to engage the RST on the amplitude and latency of electromyographic responses in multiple lower limb muscles such as the quadriceps femoris, hamstrings, soleus, and tibialis anterior bilaterally during locomotion in individuals with and without SCI. In Aim

2, we propose to test the effects of a novel intervention that uses repeated paired loud auditory and electrical stimulation of muscle afferents combined with locomotor training on walking speed and voluntary muscle strength. Here, individuals with chronic incomplete SCI will be randomly assigned to a group that will receive 10

sessions of a startle stimulus and electrical stimulation combined with locomotor training or 10 sessions of a non- startle stimulus combined with locomotor training. Taken together, the results of these studies will provide fundamental information about the contributions of the RST to locomotion in humans with and without SCI and will furthermore open novel avenues for improving

locomotor function in individuals living with paralysis due to SCI.