Effects of Cerebral Blood Flow and Temperature on Executive Function During Moderate Hyperthermia
Schultz Martins, Ricardo
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This thesis tested whether executive function using five different cognitive tests (Groton Maze Learning Test, 2-Back Test, Detection Test, Set Shifting and Groton Maze Learning Test recall) during passive heat stress may be affected by changes in cerebral blood flow (CBF) as opposed to thermal perception changes. An end-tidal forcing system was used to maintain eucapnia and baseline CBF in the isocapnic trial during the hypocapnia-induced CBF reduction. Repeated measures analysis of variance indicated that an increase of 5°C in mean skin temperature impaired working memory regardless of rectal temperature. The results also indicated that an increase of 1.5°C in rectal temperature increases the amount of errors by 38% when compared to baseline regardless of mean skin temperature. Although eucapnia was maintained during hyperthermia, it did not preserve baseline levels of mean middle cerebral artery velocity, indicating that changes in CBF are not the main hyperthermia-induced impairment factor for EF. In conclusion, increased skin temperature impaired working memory and increased rectal temperature impaired cognitive flexibility. In addition, as EF impairments were seen before any changes in CBF, it indicates that a decrease in CBF is not the main hyperthermia-induced impairment factor for EF.