Neuroplastic mechanisms of dysphagia following stroke: Effects of aging and tongue exercise treatment

About This Grant

Project Summary Dysphagia (difficulty swallowing) commonly occurs after stroke and is an independent predictor of poor outcomes, need for long term care, and high healthcare costs. The recovery of oral-motor function after stroke is critical for both health and quality of life, yet the majority of post-stroke swallowing problems persist beyond 6 months and clinical care is often limited to compensatory strategies versus active treatment of underlying mechanisms. Neural and muscular plasticity allow for substantial recovery of motor function after stroke and optimization of plasticity is a primary target of most rehabilitation strategies. However, most of what we know about neuromuscular plasticity after stroke is specific to the corticospinal tract – plasticity of the corticobulbar tract and cranial muscles that support swallowing function are understudied. A better understanding of the unique mechanisms of corticobulbar neuromuscular plasticity after stroke is needed as this knowledge gap is a limiting factor to improving active treatments for dysphagia. Further, stroke most commonly occurs in aged individuals and thus understanding interactions between age and swallowing recovery is critical. Our long- term goal is to improve swallowing rehabilitation by quantifying the multilevel plastic changes that occur after unihemispheric stroke, and how these processes are impacted by age and therapeutic interventions. Many existing clinical treatments target the tongue as lingual weakness is commonly associated with post stroke dysphagia. Tongue exercise has the potential to improve lingual strength and swallowing outcomes after stroke, yet there is no consensus on efficacy or optimal methods. This work proposes examination of swallowing behaviors as well as putative muscular, brainstem, and cortical mechanisms of exercise-based plasticity using a translational rat model of post-stroke dysphagia. Based on our previous findings that demonstrate post-exercise changes in lingual and cortical measures, our hypothesis is that tongue exercise will significantly improve lingual muscle activation and function through both neural and muscular plasticity across the age range, but older age will significantly limit these improvements. Aim 1 will quantify the impact of tongue exercise on lingual activation, muscle strength, and swallowing function after stroke. Aim 2 will establish mechanisms of brainstem and cortical plasticity associated with lingual rehabilitation exercises. Together, these aims will determine the impact of age on neural and muscular plasticity induced by tongue exercise after stroke. This innovative research will generate foundational knowledge on the neuromuscular effects of post-stroke tongue exercise that will inform future studies (clinical and pre-clinical) seeking to improve the rehabilitation of post-stroke dysphagia by identifying specific biological targets and leading to more optimized, efficient, and targeted treatment approaches.