title: Effects of prolonged head-down bed rest on working memory.
abstract: BACKGROUND
  The weightlessness caused by prolonged bed rest results in changes in cerebral circulation and thus, brain functions, which is of interest.
  
  
  METHODS
  We investigated the effects of 45-day, -6° head-down bed rest, which stimulated microgravity, on working memory in 16 healthy male participants. The 2-back task was used to test the working memory variations on the 2nd day before bed rest (R-2); on the 11th (R11), 20th (R20), 32nd (R32), and 40th (R40) days of bed rest; and on the eighth day after bed rest (R+8). The cognitive response and the physiological reactivity (such as galvanic skin response, heart rate, and heart rate variability) under the 2-back task were recorded simultaneously.
  
  
  RESULTS
  The results showed that compared with R-2, on the R+8, the participants' galvanic skin response increased significantly, and the high frequency of heart rate variability (HF), low frequency of heart rate variability (LF), and reaction time in the 2-back task decreased significantly. There were positive correlations between the participants' reaction time of working memory and the LF/HF under head-down bed rest (at R11, R20, and R32).
  
  
  CONCLUSIONS
  The results suggested that the prolonged head-down bed rest may have a detrimental effect on individual physiology and working memory. Physiology indices, such as galvanic skin response and heart rate variability, were sensitive to the prolonged bed rest.
authors.affiliation: Beijing Key Lab of Applied Experimental Psychology, School of Psychology, Beijing Normal University, Beijing, People's Republic of China ; Research Center of Emotion Regulation, Beijing Normal University, Beijing, People's Republic of China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Liu
authors.affiliation: Beijing Key Lab of Applied Experimental Psychology, School of Psychology, Beijing Normal University, Beijing, People's Republic of China ; Research Center of Emotion Regulation, Beijing Normal University, Beijing, People's Republic of China ; State Key Laboratory of Cognitive Neuroscience and Learning, International Data Group/McGovern Institute for Brain Research, Beijing Normal University, Beijing, People's Republic of China ; Department of Psychology, School of Social and Behavioral Science, Nanjing University, Nanjing, People's Republic of China.
authors.forename: Renlai
authors.initials: R
authors.lastname: Zhou
authors.affiliation: Behavior Rehabilitation Training Research Institution, School of Psychology, Northwest Normal University, Lanzhou, People's Republic of China.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhao
authors.affiliation: School of Psychology, University of Queensland, Brisbane, QLD, Australia.
authors.forename: Tian Po S
authors.initials: TP
authors.lastname: Oei
keywords: galvanic skin response; heart rate; heart rate variability
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