Changes in reaction time, coefficient of variance of reaction time, and autonomic nerve function in the mental fatigue state caused by long-term computerized Kraepelin test workload in healthy volunteers

Daisuke Kuratsune, Seiki Tajima, Junichi Koizumi, Kouzi Yamaguti, Tetsuya Sasabe, Kei Mizuno, Masaaki Tanaka, Naoko Okawa, Hideki Mito, Hirokazu Tsubone, Yasuyoshi Watanabe, Masayasu Inoue, Hirohiko Kuratsune

Clinical Center for Fatigue Science, Graduate School of Medicine, Osaka City University, Osaka, Japan.
Department of Biochemistry and Molecular Pathology, Graduate School of Medicine, Osaka City University, Osaka, Japan.
Department of Comparative Pathophysiology, Veterinary Medical Sciences, Graduate School of Agricultural & Life Science, The University of Tokyo, Tokyo, Japan.
Department of Physiology, Graduate School of Medicine, Osaka City University, Osaka, Japan.
Division of Materials Science and Chemical Engineering, Yokohama National University, Yokohama, Japan.
Faculty of Health Science for Welfare, Kansai University of Welfare Sciences, Kasiwara, Japan.
Hyogo Children’s sleep and development medical research center, Kobe, Japan.
RIKEN, Center for Molecular Imaging Science, MI R&D Center, Kobe, Japan.

DOI: 10.4236/wjns.2012.22016                

Abstract

Fatigue is a common sense caused by crushing labor, stressful social events and various illnesses. It is usually judged by their subjective symptoms, but it should be evaluated in an objective perspective. Here we show that the decrease of working efficiency and sympathetic hyperactivity are associated with mental fatigue state caused by prolonged mental workload. Recently we made a new mental fatigue model of healthy volunteers caused by long-term computerized Kraepelin test (CKT) workload. CKT is our new software for automatically checking the calculation capability, with which it is easy to determine the reaction time (RT), coefficient of variance of reaction time (CV), and accuracy of the answers (AC) during tasks. We put 24 healthy volunteers into the fatigue state by subjecting them to 120 minutes’ CKT workload, and then studied the changes in fatigue sensation, RT, CV, and AC before and after the CKT workload. The fatigue sensation, RT, and CV were clearly increased by the fatigue-inducing task and recovered during the resting period. We also studied the changes in autonomic nerve activity by using heart rate variability analysis. The low/high frequency component ratio (LF/HF) was signifi-cantly increased by the fatigue-inducing task and decreased by resting, suggesting that mental stress causes a relatively sympathetic nerve activity-dominant state. Therefore, our new fatigue model involving a long-term CKT workload is a good mental fatigue model to provide much information about the fatigue state simultane-ously, and the increase of RT, CV, and proportion of sympathetic activity (LF/HF) are associated with mental fatigue state. These might be useful objective biomarkers or evaluating a mental fatigue state.

Keywords

Fatigue; Computerized Kraepelin Test; Reaction Time; Accuracy of the Answers; Autonomic Nerve Activity

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Uchiyama, S. Kurasawa, T. Sekizawa T. and Nakatsuka H. (2005) Job strain and risk of cardiovascular events in treated hypertensive Japanese workers: Hypertension follow-up group study. Journal of Occupational Health, 47, 102-111. doi:10.1539/joh.47.102
[2]	Mizuno-Lewis, S. and McAllister, M. (2008) Taking leave from work: The impact of culture on Japanese female nurses. Journal of Clinical Nursing, 17, 274-281.
[3]	Iwasaki, K., Takahashi, M. and Nakata. A. (2006) Health problems due to long working hours in Japan: working hours, workers’ compensation (Karoshi), and preventive measures. Industrial Health, 44, 537-540. doi:10.2486/indhealth.44.537
[4]	Watanabe, Y. (2008) Preface and mini-review: Fatigue science for human health. In: Watanabe, Y., Evengard, B., Natelson, B.H., Jason, L.A. and Kuratsune, H., Eds., Fatigue Science for Human Health, Springer, New York, 5-11.
[5]	Tanaka, M., Mizuno, K., Yamaguti, K., Kuratsune, H., Fujii, A., Baba, H., Matsuda, K., Nishimae, A., Takesaka, T. and Watanabe, Y. (2011) Autonomic nervous alterations associated with daily level of fatigue. Behavioral and Brain Functions, 7, 46. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3214128/pdf/1744-9081-7-46.pdf
[6]	Mizuno, K., Tanaka, M., Yamaguti, K., Kajimoto, O., Kuratsune, H. and Watanabe, Y. (2011) Mental fatigue caused by prolonged cognitive load associated with sympathetic hyperactivity. Behavioral and Brain Functions, 7, 17. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3113724/pdf/1744-9081-7-17.pdf
[7]	Lee, K.A., Hicks, G. and Nino-Murcia, G. (1991) Validity and reliability of a scale to assess fatigue. Psychiatry Research, 36, 291-298. doi:10.1016/0165-1781(91)90027-M
[8]	Shinba, T., Kariya, N., Matsui, Y., Ozawa, N., Matsuda, Y. and Yamamoto, K. (2008) Decrease in heart rate variability response to task is related to anxiety and depressiveness in normal subjects. Psychiatry and Clinical Neurosciences, 62, 603-609. doi:10.1111/j.1440-1819.2008.01855.x
[9]	Ihaka, R. and Gentleman, R. (1996) A language for data analysis and graphics. Journal of Computational and Graphical Statistics, 5, 299-314.
[10]	Ataka, S., Tanaka, M., Nozaki, S., Mizuma, H., Mizuno, K., Tahara, T., Sugino, T., Shirai, T., Kajimoto, Y., Kuratsune, H., Kajimoto, O. and Watanabe, Y. (2008) Effects of oral administration of caffeine and D-ribose on mental fatigue. Nutrition, 24, 233-238. doi:10.1016/j.nut.2007.12.002
[11]	Stefank, K. (1923) Reaction time and fatigue. Science, 57, 204-205. doi:10.1126/science.57.1468.204-a
[12]	Akselrod, S., Gordon, D., Ubel, F.A., Shannon, D.C., Berger, A.C. and Cohen, R.J. (1981) Power spectrum analysis of heart rate fluctuation: A quantitative probe of beat-to-beat cardiovascular control. Science, 213, 220-222. doi:10.1126/science.6166045
[13]	Pagani, M., Furlan, R., Pizzinelli, P., Crivellaro, W., Cerutti, S. and Malliani, A. (1989) Spectral analysis of R-R and arterial pressure variabilities to assess sympathovagal interaction during mental stress in humans. Journal of Hypertension, 6S, 14-15.
[14]	Lucini, D., Di Fede, G., Parati, G. and Pagani, M. (2005) Impact of chronic psychosocial stress on autonomic cardiovascular regulation in otherwise healthy subjects. Hypertension, 46, 1201-1206. doi:10.1161/01.HYP.0000185147.32385.4b
[15]	Filaire, E., Portier, H., Massart, A., Ramat, L. and Teixeira, A. (2010) Effect of lecturing to 200 students on heart rate variability and alpha-amylase activity. European Journal of Applied Physiology, 108, 1035-1043. doi:10.1007/s00421-009-1310-4
[16]	Kuratsune, H., Yamaguti, K., Lindh, G., Eveng?rd, B., Hagberg, G., Matsumura, K., Iwase, M., Onoe, H., Takahashi, M., Machii, T., Kanakura, Y., Kitani, T., L?ngstr?m, B. and Watanabe, Y. (2002) Brain regions involved in fatigue sensation: Reduced acetylcarnitine uptake into the brain. Neuroimage, 17, 1256-1265. doi:10.1006/nimg.2002.1260
[17]	Tajima, S., Yamamoto, S., Tanaka, M., Kataoka, Y., Iwase, M., Yoshikawa, E., Okada, H., Onoe, H., Tsukada, H., Kuratsune, H., Ouchi, Y. and Watanabe, Y. (2010) Medial orbitofrontal cortex is associated with fatigue sensation. Neurology Research International, 2010, Article ID 671421. doi:10.1155/2010/671421 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3003967/pdf/NRI2010-671421.pdf