Relationship Between Hand Motor and Cognitive Functions in Elderly People: A Functional Near-Infrared Spectroscopy Study

Previous studies have suggested a correlation between cognitive functions such as executive function and hand motor function, while there are few empirical studies on the direct relationship between these functions and brain activity. Therefore, this study aimed to investigate the relationship between hand motor function and brain activity by measuring and analyzing brain activity during hand motor and cognitive tasks. Twenty young men and 19 elderly men over the age of 65 participated in this experiment. The hand motor tasks included a grip strength test, a Purdue Pegboard Test, and a finger tapping task, while the cognitive tasks included the Mini-Addenbrooke's Cognitive Examination (M-ACE), a flanker task, and a working memory task. Brain activity in regions including the prefrontal cortex (PFC) during the cognitive tasks was measured using functional near-infrared spectroscopy (fNIRS). Correlation analysis between the hand motor scores and the cognitive task scores showed a significant positive correlation between the pegboard assembly score and the M- ACE score only in the elderly. In addition, we found a significant negative correlation between age and reaction time on the cognitive tasks. These results confirm that elderly people with high dexterity have higher cognitive function. Furthermore, the correlation analysis with brain activity showed a significant negative correlation between the mean activation of the left PFC during the working memory task and the assembly score in the elderly. This result suggests that brain activity was higher in elderly people with lower dexterity.