Changes in EEG signals during the cognitive activity at varying air temperature and relative humidity

Abstract

In this study, we examined changes in EEG signals during the cognitive activity at different air temperatures and relative humidities (RH). Thirty-two healthy young people acclimatized to the subtropical climate of Changsha, China, were recruited as subjects. They experienced four air temperature levels (26, 30, 33, and 37°C) and two relative humidity levels (50 and 70%) in a climate chamber. During 175 min-long exposures to each thermal condition, they performed cognitive tasks and their EEG signals were measured. Relative humidity of 70% and increased temperature at this relative humidity significantly increased the relative power of δ-band and significantly decreased relative power of θ-band, α-band, and βband. This may suggest that subjects were more sleepy but less drowsy, and it was more difficult for them to think clearly. At the same time, subjective evaluations indicated that they could be less alert and it was harder for them to think. However, no changes in performance of tasks measuring cognitive abilities were observed. It remains therefore unclear whether EEG can be a credible marker of changes in cognitive activity as a result of changes in indoor environmental quality in buildings and the future experiments should closely examine this issue.

Decreased humidity improves cognitive performance at extreme high indoor temperature

“…It included a t-shirt, thin trousers, sports shoes, socks, and underwear yielding the clothing insulation of about 0.39clo. 24 Subjects were paid the fixed salary at neutral temperature, and we referred to the actual exposure time to pay the subjects at high temperatures. It ensured that the subjects can conscientiously complete each item of the experiment.…”

“…The perceived air freshness was evaluated with a continuous scale from 0 to 100, in which 0 and 100 denoted stuffy and fresh air, Subjective questionnaire used in this experiment had been widely applied in the existing literatures. 24,43,44…”

“…Interestingly, according to our previous study carried out in hot and humid region in China, we did not observe any significant change in the accuracy of some typical cognitive tasks even when the indoor temperature increased to 37°C with high RH of 70%. 24 Additionally, the extreme high indoor air temperature can rise above 38°C during the summer in hot-humid region from field data collected in 2005 and 2017. 1,4 Therefore, taking the above factors into account, the high temperature was set as 39°C in the present study.…”

Exploring a sustainable building’s impact on occupant mental health and cognitive function in a virtual environment

“…CLT is a theoretical framework based on previous knowledge of human cognitive architecture in the brain 18 , which includes long-term memory and working memory. CLT comprises two types of cognitive loads: intrinsic load and extrinsic load 19 , with intrinsic load defined by the nature of the task itself, and extrinsic load determined by the way in which the task is presented 14 , including in which type of environment the task is presented. Plass and Van Merriënboer proposed a CLT model in 1994 20 and revised it in 2014 to include a "physical learning environment, " which is disentangled from "learning tasks" and "learning environment" in order to describe the physical characteristics of the built environment in which cognitive tasks (such as learning) happen 15,16 .…”

“…Also, applying EEG/ERP to study the cognitive effect from stimulus in building to occupant is limited. Most recently, a few studies utilizing EEG measure the impact of indoor thermal environment (temperature, humidity) on human's cognitive function [12][13][14] . The cognitive functions studies include semantic thinking, visual perception, spatial reasoning and spatial working memory 15 .…”