title: Fatigue correlates with the decrease in parasympathetic sinus modulation induced by a cognitive challenge.
abstract: BACKGROUND
  It is known that enhancement of sympathetic nerve activity based on a decrease in parasympathetic nerve activity is associated with fatigue induced by mental tasks lasting more than 30 min. However, to measure autonomic nerve function and assess fatigue levels in both clinical and industrial settings, shorter experimental durations and more sensitive measurement methods are needed. The aim of the present study was to establish an improved method for inducing fatigue and evaluating the association between it and autonomic nerve activity.
  
  
  METHODS
  Twenty-eight healthy female college students participated in the study. We used a kana pick-out test (KPT) as a brief verbal cognitive task and recorded electrocardiography (ECG) to measure autonomic nerve activity. The experimental design consisted of a 16-min period of ECG: A pre-task resting state with eyes open for 3 min and eyes closed for 3 min, the 4-min KPT, and a post-task resting state with eyes open for 3 min and eyes closed for 3 min.
  
  
  RESULTS
  Baseline fatigue sensation, measured by a visual analogue scale before the experiment, was associated with the decrease in parasympathetic sinus modulation, as indicated the by ratio of low-frequency component power (LF) to high-frequency component power (HF), during the KPT. The LF/HF ratio during the post-KPT rest with eyes open tended to be greater than the ratio during the KPT and correlated with fatigue sensation. Fatigue sensation was correlated negatively with log-transformed HF, which is an index of parasympathetic sinus modulation, during the post-KPT rest with eyes open.
  
  
  CONCLUSIONS
  The methods described here are useful for assessing the association between fatigue sensation and autonomic nerve activity using a brief cognitive test in healthy females.
authors: Pathophysiological and Health Science Team, RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan. keimizuno@riken.jp.
authors: Kei
authors: K
authors: Mizuno
authors: Kanako
authors: K
authors: Tajima
authors: Yasuyoshi
authors: Y
authors: Watanabe
authors: Hirohiko
authors: H
authors: Kuratsune
mesh_terms: D003071:Cognition; D004562:Electrocardiography; D005221:Fatigue / Q000503:physiopathology* / Q000523:psychology*; D005260:Female; D006801:Humans; D008960:Models, Psychological; D010275:Parasympathetic Nervous System / Q000503:physiopathology*; D011597:Psychomotor Performance; D055815:Young Adult