A Potential Role for Oxygen in the Development of Mental Fatigue and the Subsequent Decline in Cognitive Performance

Study Overview
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Brief Summary
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Introduction Both Mental Fatigue (MF) and hypoxia impair multiple aspects of cognitive functioning. The decline in cognitive functioning in hypoxic conditions is associated with alterations in brain oxygenation and hemodynamic responses. These hemodynamic responses are preferably measured at the prefrontal cortex, an area of the brain that is known for its executive function and role in decision making, planning, attention and (short-term) memory. This study will investigate the role of prefrontal cortex oxygenation during the development of mental fatigue and during cognitive performances by altering the ambient oxygen availability through normobaric hypoxia (3800m; 12,9% O2) and normoxia. Methods Subjects will perform four trials in a sound-insulated climate chamber (20°C and 40% RH). Upon entry in the climatic chamber participants will adapt to the environment for 30 minutes. Next, they will perform a modified cognitive test battery cognition, a fine motor task Motor Performance Series and a visuomotor-fitlight task before and after a 60-minute individualized Stroop task or control task (randomized. blinded, placebo controlled, counter-balanced, cross-over design). Nearinfrared spectroscopy (NIRS) will be used to assess hemodynamic changes (oxygenated hemoglobin (O2Hb), deoxygenated-hemoglobin (HHb) and total hemoglobin (tHb)) at the PFC. Hypotheses 1) MF will lead to earlier changes in the prefrontal NIRS-parameters (O2Hb, HHb, tHb) with lower oxygen availability. 2) The effects of MF on cognitive performance manifest itself to a greater extent with lower oxygen availability.3) Visuomotor performance declines to a greater extent due to MF with lower oxygen availability.

Official Title
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A Potential Role for Oxygen in the Development of Mental Fatigue and the Subsequent Decline in Cognitive Performance

Conditions
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Mental Fatigue, Near Infrared Spectroscopy, NIRS, Hypoxia, Cerebral Heamodynamics, Cognition

Intervention / Treatment
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* Other: Hypoxia
* Other: Normoxia


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Healthy (No neurological or cardiovascular disorders) Male or female No medication Non-smoker Between 18 and 35 years old Recreational athlete population; performance level 2 or 3 for men according to De Pauw et al. (2013)[29] and performance level 2 or 3 for woman according to Decroix et al. (2015) Non-acclimatized to altitude (at least 2 months) Exclusion Criteria: Injuries Acclimated to altitude Use of medication Use of caffeine and heavy efforts 24 hours prior each trial Not eating a standardized meal, the morning of each trial

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 45 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: randomized blinded placebo-controlled counterbalanced crossover design
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Mental fatigue<br>Stroop task | Other: Hypoxia<br>* altitude (3800m)<br>* Other names: Mental fatigue;Other: Normoxia<br>* sea level<br>* Other names: Mental fatigue;|
| Placebo Comparator: Control MF<br>Emotionally neutral documentary | Other: Hypoxia<br>* altitude (3800m)<br>* Other names: Mental fatigue;Other: Normoxia<br>* sea level<br>* Other names: Mental fatigue;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Cerebral oxygenation | Prefrontal cortex oxygenation = relative changes in oxy- and deoxy hemoglobin at the prefrontal cortex. During the whole frame, participants are equipped with a Near Infrared Spectroscopy device that measures cerebral oxygenation continuously at 10hz. | 2 hours | 
| Mental fatigue | Results of a visual analogue scale for mental fatigue | 60 minutes | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Cognition | Results of the Joggle cognition test battery (accuracy and reaction time | 20 minutes | 
| Fine motor control | Results of the vienna test system (MLS) =accuraccy and reaction time | 5 minutes | 
| Visuomotor control | Results of a visuomotor fitlight task = accuracy and reaction time | 7 minutes |