Relationship between prefrontal oxygenation during task-set period and executive function in healthy older people: A...

In past research, we have examined the characteristics of brain activity caused by prefrontal task completion in healthy older adults in a simplified manner using a near-infrared spectroscopy device, with the aim of identifying methods of early intervention to prevent their cognitive decline. Previously, we reported that prefrontal oxygenation during pre-task preparation was greater in young adults than older adults, and that this greater activation was associated with better task performances in both groups. To extend this research, in the present study, we examined previous findings with task repetitions, as older adults take more time to become familiar new tasks.

We modified the working memory task with a clear task-set instruction and examined the change in the task-set and task-induced activation in 63 cognitively healthy older adults.

Task-set activation did not increase even after three repetitions, and the task-induced activation was greater than task-set activation in most channels. The difference in degree between task-induced activation and task-set activation showed a reduction with task repetitions. Significant inverse correlations were observed between the prefrontal activation due to the task itself in the third session, i.e., after task repetitions and the reaction time of the Trail Making Test, which represents attentional function.

These results indicate that continued activation by the task itself, which persists even after older adults become familiar with the task, may be associated with executive function decline.