We examine whether the age bias of the motor imagery effect can be corrected by considering the motor imagery strategy. Therefore, the purpose of this study was to assess excitatory changes in spinal motor nerve function during motor imagery and to identify motor imagery-induced changes in finger dexterity, taking into account the possibility of age bias.
Eight young (male:4, female:4, age:21.0±0.5) and eight elderly (male:4, female;4, age:69.5±2.3) subjects were recruited. In accordance with the Declaration of Helsinki, the subjects of this study were fully informed of the content of the study and their written consent for the measurements was obtained. In addition, approval was obtained from the Kansai university of health science’s Research Ethics Review Committee (Ethics No. 24-09). First, working memory was assessed by the number of digits that could be recited backward from opposite directions, and two group comparisons were made with no correspondence between elderly and younger participants. Then, we evaluated excitatory changes in spinal motor nerve function using F waves as a modulation of the neural substrate during motor imagery (30 sec) compared to rest (30 sec). The motor imagery(MI) was induced not only by kinesthetic motor imagery but also by information indirectly associated with myosensation. Motor skills were assessed before and after the motor imagery, and the number of pins that could be inserted in 30 seconds with the left hand, the non-dominant hand, was evaluated using the Peg task. Groups by age (Elderly or Younger) and time series data (Rest or MI; Pre-MI or Post-MI) were compared using Two-way ANOVA with generalized linear mixed models.
Working memory (number of digits that could be recited backward) was lower in the elderly than in the younger. (Elderly 4.3±1.1, Young 5.9±0.9; p=0.009, r=0.63). F/M amplitude ratio showed no interaction (F(1,14)=0.239, p=0.633, η2p =0.017), and the main effect test showed an increase during the exercise imagery compared to Rest (Rest 1.1(0.7-1.5), MI 1.5(0.9-2.1); p=0.046, r=0.71). Peg score also showed no interaction (F(1,14)=0.033, p=0.859, η2p =0.002), and the main effect test showed an improvement after imagery compared to before imagery(Pre MI 14.5(11.0-16.0), Post MI 15(13.0-18.3); p=0.006, r=0.63).
Motor imagery was effective in terms of excitability of spinal motor nerve function and finger dexterity, and age bias in this case was correctable.
Although the elderly have impaired working memory function, they can reap the benefits of motor imagery in terms of excitability of spinal motor nerve function and hand dexterity by devising strategies to implement motor imagery.
F wave
finger dexterity
