Cognitive functions and cerebral oxygenation changes during acute and prolonged hypoxic exposure

• Published in: Physiology & behavior Vol. 164; no. Pt A; pp. 189 - 197
• Main Authors: Davranche, Karen, Casini, Laurence, Arnal, Pierrick J., Rupp, Thomas, Perrey, Stéphane, Verges, Samuel
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.10.2016; Elsevier
• Subjects: Adaptation, Physiological - physiology; Adult; Altitude; Cerebrovascular Circulation - physiology; cognition; Cognition - physiology; Cognitive science; Conflict (Psychology); Conflict task; Decision Making - physiology; Executive Function - physiology; Hemodynamic response; hemodynamics; Humans; Hypoxia; Hypoxia - metabolism; Hypoxia - psychology; Judgment - physiology; Male; males; near-infrared spectroscopy; Neuropsychological Tests; Neuroscience; NIRS; Oxygen - blood; prefrontal cortex; Prefrontal Cortex - blood supply; Prefrontal Cortex - metabolism; Psychiatry; Reaction Time - physiology; Reaction time distribution; sea level; Spectroscopy, Near-Infrared; Surveys and Questionnaires; Time estimation; Time Perception - physiology; NIRS; Hypoxia; Conflict task; Time estimation; Reaction time distribution; Hemodynamic response
• ISSN: 0031-9384; 1873-507X; 1873-507X
• DOI: 10.1016/j.physbeh.2016.06.001

The present study aimed to assess specific cognitive processes (cognitive control and time perception) and hemodynamic correlates using functional near-infrared spectroscopy (fNIRS) during acute and prolonged high-altitude exposure. Eleven male subjects were transported via helicopter and dropped at 14 272 ft (4 350 meters) of altitude where they stayed for 4 days. Cognitive tasks, involving a conflict task and temporal bisection task, were performed at sea level the week before ascending to high altitude, the day of arrival (D0), the second (D2) and fourth (D4) day at high altitude. Cortical hemodynamic changes in the prefrontal cortex (PFC) area were monitored with fNIRS at rest and during the conflict task. Results showed that high altitude impacts information processing in terms of speed and accuracy. In the early hours of exposure (D0), participants displayed slower reaction times (RT) and decision errors were twice as high. While error rate for simple spontaneous responses remained twice that at sea level, the slow-down of RT was not detectable after 2 days at high-altitude. The larger fNIRS responses from D0 to D2 suggest that higher prefrontal activity partially counteracted cognitive performance decrements. Cognitive control, assessed through the build-up of a top-down response suppression mechanism, the early automatic response activation and the post-error adjustment were not impacted by hypoxia. However, during prolonged hypoxic exposure the temporal judgments were underestimated suggesting a slowdown of the internal clock. A decrease in cortical arousal level induced by hypoxia could consistently explain both the slowdown of the internal clock and the persistence of a higher number of errors after several days of exposure. •Concomitant cognitive performance and hemodynamic response were investigated during high-altitude exposure•Hypoxia impacted processes involved in cognitive control as well as in temporal judgments•Prefrontal cortex activity measured with NIRS may counteract the deleterious effects of hypoxia