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Open Access Research

Two types of mental fatigue affect spontaneous oscillatory brain activities in different ways

Yoshihito Shigihara1, Masaaki Tanaka1*, Akira Ishii1, Etsuko Kanai2, Masami Funakura2 and Yasuyoshi Watanabe13

Author Affiliations

1 Department of Physiology, Osaka City University Graduate School of Medicine, 1-4-3 Asahimachi, Abeno-ku, Osaka City, Osaka, 545-8585, Japan

2 Digital & Network Technology Development Center, Panasonic Co., Ltd, 1006 Kadoma, Kadoma City, Osaka, 571-8501, Japan

3 RIKEN Center for Molecular Imaging Science, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe City, Hyogo, 650-0047, Japan

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Behavioral and Brain Functions 2013, 9:2  doi:10.1186/1744-9081-9-2

Published: 10 January 2013

Abstract

Background

Fatigue has a multi-factorial nature. We examined the effects of two types of mental fatigue on spontaneous oscillatory brain activity using magnetoencephalography (MEG).

Methods

Participants were randomly assigned to two groups in a single-blinded, crossover fashion to perform two types of mental fatigue-inducing experiments. Each experiment consisted of a 30-min fatigue-inducing 0- or 2-back test session and two evaluation sessions performed just before and after the fatigue-inducing mental task session.

Results

After the 0-back test, decreased alpha power was indicated in the right angular gyrus and increased levels in the left middle and superior temporal gyrus, left postcentral gyrus, right superior frontal gyrus, left inferior frontal gyrus, and right medial frontal gyrus. After the 2-back test, decreased alpha power was indicated in the right middle and superior frontal gyrus and increased levels in the left inferior parietal and superior parietal lobules, right parahippocampal gyrus, right uncus, left postcentral gyrus, left middle frontal gyrus, and right inferior frontal gyrus. For beta power, increased power following the 0-back test was indicated in the left middle temporal gyrus, left superior frontal gyrus, left cingulate gyrus, and left precentral gyrus. After the 2-back test, decreased power was suggested in the left superior frontal gyrus and increased levels in the left middle temporal gyrus and left inferior parietal lobule. Some of these brain regions might be associated with task performance during the fatigue-inducing trials.

Conclusions

Two types of mental fatigue may produce different alterations of the spontaneous oscillatory MEG activities. Our findings would provide new perspectives on the neural mechanisms underlying mental fatigue.

Keywords:
Magnetoencephalography (MEG); Mental fatigue; n-back test visual analogue scale (VAS)