Bimanual digit training improves right-hand dexterity in older adults by reactivating declined ipsilateral motor-cortical inhibition

Abstract

Improving deteriorated sensorimotor functions in older individuals is a social necessity in a super-aging society. Previous studies suggested that the declined interhemispheric sensorimotor inhibition observed in older adults is associated with their deteriorated hand/finger dexterity. Here, we examined whether bimanual digit exercises, which can train the interhemispheric inhibitory system, improve deteriorated hand/finger dexterity in older adults. Forty-eight healthy, right-handed, older adults (65–78 years old) were divided into two groups, i.e., the bimanual (BM) digit training and right-hand (RH) training groups, and intensive daily training was performed for 2 months. Before and after the training, we evaluated individual right hand/finger dexterity using a peg task, and the individual state of interhemispheric sensorimotor inhibition by analyzing ipsilateral sensorimotor deactivation via functional magnetic resonance imaging when participants experienced a kinesthetic illusory movement of the right-hand without performing any motor tasks. Before training, the degree of reduction/loss of ipsilateral motor-cortical deactivation was associated with dexterity deterioration. After training, the dexterity improved only in the BM group, and the dexterity improvement was correlated with reduction in ipsilateral motor-cortical activity. The capability of the brain to inhibit ipsilateral motor-cortical activity during a simple right-hand sensory-motor task is tightly related to right-hand dexterity in older adults.

Effects of home-based manual dexterity training on cognitive function among older adults: a randomized controlled trial

“…The present study is one of the first intervention studies to examine the effects of home-based manual dexterity training (i.e., grasping and moving an object with visual information) using a digital trail-making peg test device on cognitive function and manual dexterity among older adults. Compared to a previous study using manual dexterity training [ 12 ], the present intervention did not significantly enhance simple manual dexterity (number of pegs on right, left, and both hands) in the intervention group, although a moderate effect size for the performance changes of both hands (Cohen’s d = 0.57) was observed. In contrast, the performance in the complex manual dexterity task (e.g., assembly task) improved in the intervention group (Table 2 ).…”

“…Performing tasks that require manual dexterity activates the prefrontal cortex, primary motor cortex, and primary sensorimotor cortex in older adults [ 1 , 12 , 13 ]. The primary motor cortex and corticomotoneuronal cells that synapse directly onto spinal motor neurons, bypassing the spinal interneurons, are involved in manual dexterity; hand movement with visual information involves the primary motor cortex and associated neurons [ 1 ].…”

“…Another intervention study lasting 2 months reported the effects of manual dexterity training (i.e., involved finger extension, counting, rotation, rock-paper-scissors, and shape generation) on manual dexterity and cognitive function. Compared to the only dominant training group, the training group using both hands improved manual dexterity and demonstrated a more pronounced activation of the primary motor cortex during a pegging task [ 12 ]. Based on previous studies [ 12 , 17 ], it seems reasonable to hypothesize that manual dexterity training could have a positive effect on manual dexterity and executive function in older adults.…”

“…Compared to the only dominant training group, the training group using both hands improved manual dexterity and demonstrated a more pronounced activation of the primary motor cortex during a pegging task [ 12 ]. Based on previous studies [ 12 , 17 ], it seems reasonable to hypothesize that manual dexterity training could have a positive effect on manual dexterity and executive function in older adults. Interestingly, an acute experimental study revealed that compared to the easier task (control, and trail-making test (TMT) part A), the difficult task (TMT part B) shows greater activation of the prefrontal cortex (PFC) in younger adults [ 18 ].…”

Facilitation of Hand Proprioceptive Processing in Paraplegic Individuals with Long-Term Wheelchair Sports Training

“…A significant decrease in activity in the foot section of the left M1 during the passive and active tasks in the control group ( Figure 3 B) can be considered as cross-somatotopic inhibition [ 30 , 31 ], in which the brain tries to suppress the occurrence of an unintended foot movement during hand movement. In contrast, in the paraplegic group, the activity in the M1 cluster increased during the passive task across participants, except for P2 ( Figure 3 B).…”