Spectral Analysis of fMRI Signal and Noise

Abstract

Mental fatigue caused by prolonged mental work induces not only an increase in the sensation of fatigue, but also a decrease in work efficiency. However, there have been few studies measuring the extent of the decrease in work efficiency due to mental fatigue, because previously there had been no established mental task that could measure the extent of work efficiency. In this study, we used a recently developed test to investigate changes in task performance over a 4-h period by 14 healthy volunteers. The mental tasks which the subjects performed were an advanced trail making test (ATMT) and a verbal 2-back task. The ATMT consists of selective attention and spatial working memory tests. The verbal 2-back task is a simple working memory test. The results of the ATMT showed an increase in the number of errors with time spent on the task. In contrast, the performance of the verbal 2-back test did not deteriorate with time spent on the task. These results suggest that mental fatigue induces a decrease in selective attention rather than in working memory. Therefore, the ATMT may be useful for measuring the extent of work efficiency during mental fatigue. In order to develop antifatigue medications and food supplements, the ATMT may also be useful for an objective evaluation of the extent of mental fatigue, as well as a fatigue-inducing task.