Attenuated motor neuroplasticity after tongue-muscle training in older adults: A proof-of-concept study

Low tongue pressure contributes to dysphagia by compromising safe swallowing. While tongue-lift training consistently induces corticomotor plasticity in younger individuals, neuromuscular efficacy and motor neuroplasticity in older adults remain unclear. This proof-of-concept study aimed to investigate central and peripheral motor adaptations following brief tongue-lift training in older adults with low tongue pressure.

Thirteen older adults (8 women, mean age ± SD: 81 ± 4 years) with low tongue pressure (<30 kPa) underwent 41-minute standardized daily tongue-lift training over 5 consecutive days. Maximal tongue pressure was measured daily pre- and post-training. Transcranial magnetic stimulation was administered on days 1 and 5 to evaluate the resting motor threshold (MT) and motor-evoked potential (MEP) map areas of the tongue as measures of corticomotor excitability. Friedman tests were conducted to examine effects of time on outcome parameters.

The 5-day tongue training induced a significant increase in maximal tongue pressure (33.0%; P = 0.005) with a significant decrease in its coefficient of variation (-51.5%, P = 0.030), accompanied by a significant decrease in the tongue MT (-11.3%, P < 0.001). However, the tongue MEP cortical map area did not change significantly (P = 0.853).

These findings provide preliminary evidence for attenuated motor neuroplasticity following tongue-muscle training in older adults. Nevertheless, improved tongue motor function and corticobulbar excitability indicate that the potential for neurophysiological and functional adaptation remains intact. A better understanding of these age-related differences may contribute to the development of rehabilitation strategies for older adults with oral hypofunction.