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Updated: Aug 18, 2026

Coherence between Brain Cortical Function and Neurocognitive Performance during Changed Gravity Conditions
Published on: May 23, 2011
Cerebral oxygenation declines despite maintained orthostatic tolerance after brief exposure to gravitational stress
Cong Chi Denis Tran1, Muriel Berthelot, Xavier Etienne
1Département Physiologie, Institut de Médecine Aérospatiale du Service de Santé des Armées, B.P. 73, 91223 Brétigny-sur-Orge Cédex, France. dtran@imassa.fr
Abstract:
We examined the effect of a single 120 s of exposure to +3Gz (head-to-foot inertial forces) centrifugation as orthostatic stress on cerebral oxygenation (oxy-Hb) and cerebral blood volume (CBV) changes in response to stand test, in order to relate the occurrence of altered cerebral oxygenation control to any increase in sympathetic activity. Frontal near-infrared spectroscopy and mean arterial blood pressure at brain level (MAPbrain) were recorded in 14 subjects in supine and then in standing (10 min) position, before and after +3Gz centrifugation. The decrease in oxy-Hb (-7 +/- 5 a.u. versus -27 +/- 4 a.u., P<0.001) and in CBV (-6 +/- 10 a.u. versus -15 +/- 8 a.u., P<0.05) upon standing was more important after +3Gz centrifugation, with unchanged MAPbrain (-8 +/- 8 mmHg versus -3 +/- 11 mmHg). Upon standing, the high-frequency component of heart rate was lower (1090 +/- 460 ms2 versus 827 +/- 412 ms2, P<0.05) after +3Gz centrifugation. These findings suggest a downward shift in the static cerebral autoregulatory curve. We conclude that cerebral vasoconstriction might have occurred without centrally mediated increase in the entire peripheral sympathetic activity of the body.
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