Cognitive functions and cerebral oxygenation changes during acute and prolonged hypoxic exposure.
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.
Laboratoire de Psychologie Cognitive (LPC), UMR 7290, CNRS, Aix-Marseille Université, FR, 3C FR, 3512, Marseille, France. Electronic address: karen.davranche@univ-amu.fr.
Karen
K
Davranche
Laboratoire de Neurosciences Cognitives (LNC), UMR 7291, CNRS, Aix Marseille Université, FR, 3C FR, 3512, Marseille, France. Electronic address: laurence.casini@univ-amu.fr.
Laurence
L
Casini
Université de Lyon, Laboratoire de Physiologie de l'Exercice, EA4338, Saint-Étienne, France. Electronic address: pierrick.arnal@gmail.com.
Pierrick J
PJ
Arnal
HP2 Laboratory, Grenoble Alpes Université, Grenoble, France; U1042, INSERM, Grenoble, France. Electronic address: thomas.rupp@univ-savoie.fr.
Thomas
T
Rupp
Euromov, Université de Montpellier, Montpellier, France. Electronic address: stephane.perrey@umontpellier.fr.
Stéphane
S
Perrey
HP2 Laboratory, Grenoble Alpes Université, Grenoble, France; U1042, INSERM, Grenoble, France. Electronic address: SVerges@chu-grenoble.fr.
Samuel
S
Verges
D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D000531:Altitude; D002560:Cerebrovascular Circulation / Q000502:physiology; D003071:Cognition / Q000502:physiology*; D003220:Conflict, Psychological; D003657:Decision Making / Q000502:physiology; D056344:Executive Function / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000378:metabolism* / Q000523:psychology*; D007600:Judgment / Q000502:physiology; D008297:Male; D009483:Neuropsychological Tests; D010100:Oxygen / Q000097:blood*; D017397:Prefrontal Cortex / Q000098:blood supply / Q000378:metabolism*; D011930:Reaction Time / Q000502:physiology; D019265:Spectroscopy, Near-Infrared; D011795:Surveys and Questionnaires; D013998:Time Perception / Q000502:physiology
D010100:Oxygen
Conflict task; Hemodynamic response; Hypoxia; NIRS; Reaction time distribution; Time estimation