title: Mental fatigue caused by prolonged cognitive load associated with sympathetic hyperactivity.
abstract: BACKGROUND
  It is known that chronic fatigue is associated with sympathetic hyperactivity. However, the relationship between autonomic function and mental fatigue caused by a prolonged mental load in healthy humans is still unclear. Thus, in order to clarify the mechanisms underlying mental fatigue, we examined the association between mental fatigue and autonomic functions.
  
  
  METHODS
  The study group comprised 10 healthy participants. To induce mental fatigue, participants performed mental tasks, which consisted of the advanced trail making test, kana pick-out test and mirror drawing test, for 8 hr, corresponding to a normal work day. Autonomic functions were measured by accelerated plethysmography before and after the fatigue-inducing mental tasks. As a control, the same participants completed an 8-hr relaxation session 4 weeks before the fatigue session.
  
  
  RESULTS
  After the 8-hr relaxation session, low-frequency component power (LF), high-frequency component power (HF) and low-frequency component power/high-frequency component power ratio (LF/HF ratio) were not changed from baseline. In contrast, after the fatigue session, the HF and LF/HF ratio were significantly changed from baseline; specifically, the HF was lower and LF/HF ratio was higher as compared to those after the relaxation session.
  
  
  CONCLUSIONS
  Sympathetic hyperactivity based on decreased parasympathetic activity is associated with mental fatigue induced by prolonged cognitive load.
authors: Molecular Probe Dynamics Laboratory, RIKEN Center for Molecular Imaging Science, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe City, Hyogo 650-0047, Japan. keimizuno@riken.jp
authors: Kei
authors: K
authors: Mizuno
authors: Masaaki
authors: M
authors: Tanaka
authors: Kouzi
authors: K
authors: Yamaguti
authors: Osami
authors: O
authors: Kajimoto
authors: Hirohiko
authors: H
authors: Kuratsune
authors: Yasuyoshi
authors: Y
authors: Watanabe
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