Suppression of cognitive function in hyperthermia; From the viewpoint of executive and inhibitive cognitive processing

Abstract

Climate change has had a widespread impact on humans and natural systems. Heat stroke is a life-threatening condition in severe environments. The execution or inhibition of decision making is critical for survival in a hot environment. We hypothesized that, even with mild heat stress, not only executive processing, but also inhibitory processing may be impaired, and investigated the effectiveness of body cooling approaches on these processes using the Go/No-go task with electroencephalographic event-related potentials. Passive heat stress increased esophageal temperature (Tes) by 1.30 ± 0.24 °C and decreased cerebral perfusion and thermal comfort. Mild heat stress reduced the amplitudes of the Go-P300 component (i.e. execution) and No-go-P300 component (i.e. inhibition). Cerebral perfusion and thermal comfort recovered following face/head cooling, however, the amplitudes of the Go-P300 and No-go-P300 components remained reduced. During whole-body cooling, the amplitude of the Go-P300 component returned to the pre-heat baseline, whereas that of the No-go-P300 component remained reduced. These results suggest that local cooling of the face and head does not restore impaired cognitive processing during mild heat stress, and response inhibition remains impaired despite the return to normothermia.

Residual heat stress improves spatial rotation function, but does not modify attention

“…Less is known about residual heat stress effect on cognitive function when body temperature naturally recovery till normothermia. A study with a whole body cooling after heat stress (skin temperature elevation Δ 4.66 ± 0.63 o C, esophageal temperature Δ 1.30 ± 0.24 o C) involved decrease in error rate (versus heat stress condition) (Shibasaki et al, 2017). (Shibasaki et al, 2016) determined shorter reaction time, but not changed error rate compares with before when whole body cooling after heat stress (esophageal temperature Δ 2.0 o C) was induced.…”

“…That may reduce cerebral blood flow due to hypocapnia and following cerebral vasoconstriction (Nelson et al, 2011), as well as dehydration (Trangmar et al, 2014), impair brain metabolism (Nybo, Møller, Volianitis, Nielsen, & Secher, 2002); and neurophysiological properties (Shibasaki, Namba, Oshiro, Crandall, & Nakata, 2016;Shibasaki, Namba, Oshiro, Kakigi, & Nakata, 2017;Yu, Hill, & McCormick, 2012). Restricted brain blood flow (Shibasaki et al, 2016(Shibasaki et al, , 2017 and body liquids loss greater than 2% (Gopinathan, Pichan, & Sharma, 1988) could reduce mental performance. Studies with functional imaging techniques demonstrate that during intense emotional states (for example stress) neural activity in some cognitive-processing areas could be suppressed (Drevets & Raichle, 1998).…”

“…Studies with functional imaging techniques demonstrate that during intense emotional states (for example stress) neural activity in some cognitive-processing areas could be suppressed (Drevets & Raichle, 1998). Some studies suggest that the conduction velocity of the ascending somatosensory input (Nakata, Oshiro, Namba, & Shibasaki, 2015) and reaction time (Shibasaki et al, 2016) is accelerated under increased body temperature or may reduce neural activity in particular brain regions (Shibasaki et al, 2017). Stressors activate the hypothalamopituitary-adrenocortical and the sympatho-adrenal medullary axis, and increase in concentration of cortisol, adrenaline and noradrenaline is observing (McMorris et al, 2006;Minton, 1994).…”

“…(Shibasaki et al, 2016) determined shorter reaction time, but not changed error rate compares with before when whole body cooling after heat stress (esophageal temperature Δ 2.0 o C) was induced. Also cerebral perfusion was eliminated (one of the important factor influencing changes in cognitive performance) in Shibasaki et al (2016Shibasaki et al ( , 2017) studies using face/head cooling. McMorris et al (2006) determined random movement generation score was significantly poorer comparing pre and post-recovery results (heat stress increased core temperature 1.10 ± 0.11 o C, body core temperature returned to pre heat values during recovery), but no differences in choice reaction time, verbal and spatial recall scores were found, and their participants were not dehydrated.…”

“…Most of the studies examined changes of cognitive function under heat stress (Hocking, Silberstein, Lau, Stough, & Roberts, 2001;McMorris et al, 2006;Racinais, Gaoua, & Grantham, 2008;Razmjou, 1996;Shibasaki et al, 2017) or using different cooling methods after heating (McMorris et al, 2006;Shibasaki et al, 2017). However, we do not use any cool/cold stimuli, which are described as comfortable and increasing alertness (in combination with elevated body temperature (Cabanac, 1971;Nakamura et al, 2008).…”