Behavioural Brain Research 281 (2015) 111–115 Contents lists available at ScienceDirect Behavioural Brain Research jou rn al hom epage: www.elsevier.com/locate/bbr Research report The impact of chronic stress burden of 520-d isolation and confinement on the physiological response to subsequent acute stress challenge Buqing Yi a,∗ , Sandra Matzel a , Matthias Feuerecker a , Marion Hörl a , Camilla Ladinig a , Vera Abeln b , Alexander Choukèr a,∗ , Stefan Schneider b,c,∗∗ a Department of Anaesthesiology (Research Group Stress and Immunology), Hospital of the University of Munich (LMU), Munich, Germany b Institute of Movement and Neurosciences, German Sport University Cologne, Cologne, Germany c Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore, Queensland, Australia h i g h l i g h t s • We exposed the Mar520 participants and a control group to an acute stress challenge. • We observed enhanced cortical activities and elevated cortisol and adrenaline levels. • A group effect was revealed showing higher cortisol peak levels in the Mars520 group. a r t i c l e i n f o Article history: Received 29 September 2014 Received in revised form 3 December 2014 Accepted 4 December 2014 Available online 12 December 2014 Keywords: Chronic stress HPA axis activity EEG Cortisol a b s t r a c t Collective evidence indicates that previous exposure to stressful condition might be able to induce changes in brain structure, HPA axis activity and related neurotransmission, and accordingly affect phys- iological responses to subsequent challenges. During long-term spaceflight, space travelers have to live under the condition of isolation and confinement in the spacecraft for a long period. It is still largely unknown if this kind of chronic stress burden can induce any long-lasting changes. To address this question, following 520-d isolation and confinement simulating a flight to Mars, the participants and a matched control group were exposed to an acute stress challenge called parabolic flight. Brain cortical activity, HPA axis activity, and sympathetic adrenal-medullary system response were monitored by EEG signal, cortisol secretion, and catecholamine production, respectively. We observed enhanced EEG sig- nals, elevated cortisol levels and increased adrenaline productions. A group effect on cortisol output was revealed showing higher cortisol peak levels in the Mars520 group as compared to the control group, suggesting that HPA axis was to a certain extent more activated in the subjects who had chronic stress experience. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Human interplanetary travel has been anticipated for several decades. One major challenge for the success of interplanetary ∗ Corresponding author at: Department of Anaesthesiology (Research Group Stress and Immunology), Hospital of the University of Munich (LMU), Marchion- inistrasse 15, 81377 Munich, Germany. Tel.: +49 89 4400 76422; fax: +49 89 4400 78886. ∗∗ Corresponding author at: Institute for Movement and Neurosciences German Sport University Cologne Am Sportpark, Müngersdorf 6, 50933 Köln, Germany. E-mail addresses: buqing.yi@med.uni-muenchen.de (B. Yi), alexander.chouker@med.uni-muenchen.de (A. Choukèr), Schneider@dshs-koeln.de (S. Schneider). exploration is that space traveler has to be confined and isolated in the spacecraft for a long period. For example, a flight to Mars will likely take more than 500 days. It is still largely unknown how the chronic stress burden of long-term “isolation and confinement” can affect human beings physiologically, such as whether this kind of chronic stress experience has any long-lasting effect on subsequent activities. Both animal studies and a few human studies have suggested that exposure to chronic stress can induce changes in brain struc- ture (such as hippocampal volume), HPA axis activities, and related neurotransmission, which accordingly affect cognitive and emo- tional functions and alter behavioral responses [1–3]. There is a growing concern about the persistence of changes induced by chronic stress burden [2]. A few studies revealed that chronic http://dx.doi.org/10.1016/j.bbr.2014.12.011 0166-4328/© 2014 Elsevier B.V. All rights reserved.