Upregulating spinal circuits to enhance balance and walking and to increase spinal excitability in older adults

PROJECT SUMMARY/ABSTRACT A high proportion of older adults are currently or soon will be at risk for the well-known decline in walking and balance abilities that occur with aging. Preserving those abilities has become a major public health priority. Balance training can enhance functional abilities or attenuate functional decline; however, age-related motor

deficits may impair practice-based motor learning and behavioral performance. Due to the crucial roles of the spinal cord in balance and walking performance, it is important to consider that age-related neural impairment of the spinal cord is a likely contributing factor. Specifically, the spinal cord in older adults has fewer neurons, is

less excitable, and conducts signals more slowly. Despite ample evidence of impaired spinal cord neuronal structure and function with aging, the potential benefit of an intervention targeting spinal control of balance and walking control has been largely unexplored. This dearth of research may be due in part to the lack of a clinically

feasible intervention. However, the recent emergence of transcutaneous spinal direct current stimulation (tsDCS) as a non-invasive intervention creates new opportunities for understanding spinal cord contributions to balance and walking performance. The proposed study will be among the first multi-session trial to investigate the effects

of tsDCS as an adjunct therapy to dynamic balance training in older adults. We propose to include 30 participants 65-years of age or older with balance/walking deficits, who will receive active or sham tsDCS while performing a dynamic balance training intervention. Balance and walking performance assessments will be conducted after

each of the five intervention sessions to examine the intervention's effects over time. Spinal excitability will be assessed immediately before and after tsDCS at the first and last intervention sessions. Behavioral assessments will only be carried out at baseline and 1 day post-intervention to investigate the pre vs. post intervention effect,

with a 10-day period considered for the retention effect. During behavioral assessments, prefrontal cortical activity will be measured to provide insights into the demand for increased executive control. The first aim of the study will be to acquire preliminary effect size and response variance data to assess whether active adjuvant

tsDCS therapy combined with dynamic balance training enhances practice-related gains in balance and walking performance and retention over time. The second aim of the study will be to establish evidence of increased spinal excitability following tsDCS, positively correlating with gains in balance and walking functions. The

overarching hypotheses of the proposed study are that the positive effects of tsDCS on practice-related enhancements and retention in balance and walking function will be related to increased spinal excitability. The long term deliverable of this line of research will be a clinically feasible multi-modal intervention to assist in

preserving motor function and independence in older adults. The knowledge and experience gained from this study will enable us to conduct larger studies to better understand the effects of aging on the spinal cord and to test rehabilitation interventions to promote healthy aging among older adults.