Effect of Passive Hyperthermia on Working Memory Resources during Simple and Complex Cognitive Tasks

Abstract

The aim of this study was to verify the hypothesis that hyperthermia represents a cognitive load limiting available resources for executing concurrent cognitive tasks. Electroencephalographic activity (EEG: alpha and theta power) was obtained in 10 hyperthermic participants in HOT (50°C, 50% RH) conditions and in a normothermic state in CON (25°C, 50% RH) conditions in counterbalanced order. In each trial, EEG was measured over the frontal lobe prior to task engagement (PRE) in each condition and during simple (One Touch Stockings of Cambridge, OTS-4) and complex (OTS-6) cognitive tasks. Core (39.5 ± 0.5 vs. 36.9 ± 0.2°C) and mean skin (39.06 ± 0.3 vs. 31.6 ± 0.6°C) temperatures were significantly higher in HOT than CON (p < 0.005). Theta power significantly increased with task demand (p = 0.017, η2 = 0.36) and was significantly higher in HOT than CON (p = 0.041, η2 = 0.39). The difference between HOT and CON was large (η2 = 0.40) and significant (p = 0.036) PRE, large (η2 = 0.20) but not significant (p = 0.17) during OTS-4, and disappeared during OTS-6 (p = 0.87, η2 = 0.00). Those changes in theta power suggest that hyperthermia may act as an additional cognitive load. However, this load disappeared during OTS-6 together with an impaired performance, suggesting a potential saturation of the available resources.

High prevalence of hypohydration in occupations with heat stress—Perspectives for performance in combined cognitive and motor tasks

“…As demonstrated by our recent study [ 26 ] and illustrated in Fig 6 , it appears that performance in complex motor tasks is susceptible to influences through hyperthermia compared to simpler tasks and some participants displayed marked negative effects on performance in the euhydration session in the hyperthermic condition with no further effect when dehydration was superimposed. Accordingly, Gaoua and colleagues [ 43 ] suggests that complex tasks are affected by hyperthermia to a much larger extent than more stereotypical tasks. Therefore, the performance in choice reaction type of tests may remain unchanged in hyperthermic participants, maybe because some mechanisms within the neural circuitry may outweigh the negative effect of high CNS temperatures or other homeostatic disturbances influencing motor and cognitive function during severe heat stress [ 25 , 44 – 46 ].…”

Post-sauna recovery enhances brain neural network relaxation and improves cognitive economy in oddball tasks

“…N.D: Not Detected; the response of ERPs P3 component in the 80% non-target (standard) condition was too small to compute a reliable mean response for amplitude and latency. increased brain heat stress, lower blood energy supply, impairments in the brain neural network [12,13] and metabolism [14,19] have been shown to influence cognitive processing and performance [15,[40][41][42]. Indeed, when the total cognitive resources are insufficient for both the task and dealing with thermal stress [41], complex cognitive task performances that require processing for calculation, memorizing and logical thinking deteriorate [43].…”

“…Higher alpha power has been shown to be associated with reduced cortical activity and has been described as 'cortical idling', with a greater availability of resources for engagement in cognitive tasks [33]. However, as a task is engaged, alpha power activity decreases in the occipital, parietal and frontal areas of the brain [40,46] and conversely, an increase in theta power relative to rest has been reported for working memory [47] and concentration tasks [48]. However, here we did not measure theta, alpha and beta power activity during the cognitive task, as our analysis points to an absence of modification in cognitive processing (ERP components) following residual sauna recovery.…”

The reliability and validity of Bayley-III cognitive scale in China's male and female children

“…Memory is one of the primary core cognitive abilities [54][55][56][57], and language performance also has a positive influence on cognitive ability in early childhood [24]. Additionally, we observed the sex differences in children aged 18-23 months when we divided the subjects into seven age bands.…”