Mental practice of lingual resistance and cortical plasticity in older adults: An exploratory fNIRS study

Purpose: Mental practice using motor imagery (MP) improves motor strength and coordination in the upper and lower extremities in clinical patient populations. Its effectiveness as a rehabilitation tool for patients with lingual weakness is not yet well understood, nor are the underlying mechanisms within the context of swallow or lingual MP. Using previously published data on a lingual and MP exercise program, the objective of this study was to explore how MP of lingual exercise affects cortical activation in healthy older adults over time and how neural changes correlate with functional oral pressure outcomes. Method: A prospective randomized controlled study was previously completed; older healthy participants were randomized to one of four treatment groups receiving lingual MP, lingual physical practice, a combination of both, and a sham control. This paper reports descriptive data on cortical activation during both the physical and mental forms of lingual resistance in a subgroup of 13 participants using functional near-infrared spectroscopy at baseline and after 6 weeks of the assigned exercise regimen. Results: Aggregated data indicates that participants who completed 6 weeks of lingual exercise, either in physical or in MP form, had decreased oxygenated hemoglobin when completing a maximal lingual pressure task. Conclusions: Some participants in a lingual resistance MP program demonstrated trends similar to those seen after strength training. Combining MP with physical training may lead to greater changes in oxygenation compared to a physical or mental training program alone, although given the small number of participants, it is important not to overinterpret the results. MP is a promising, innovative approach that may enhance traditional exercise-based swallowing rehabilitation.