Distinct spatiotemporal patterns of EEG-estimated brain source activity associated with thermal comfort and discomfort

Thermal comfort and discomfort are important factors that activate human thermoregulatory behavior. However, little is known regarding the underlying neural mechanisms. This study examined the spatiotemporal patterns of brain source activity associated with thermal comfort and discomfort. Twelve participants received continuous whole-body thermal stimuli using a water suit perfused with cold (17°C) or hot (47°C) water (Cbody or Hbody) simultaneously with 40 repeated cycles of 32°C for 15 s and 24°C (cold) or 40°C (hot) for 10 s to the neck surface (Clocal or Hlocal). Electroencephalography (EEG) signals were recorded from 15 electrodes, and independent component analysis followed by dipole source estimation and clustering was performed. Event-related spectral perturbations were analyzed in each identified cluster to calculate spectral power changes across oscillation frequency ranges. Subjective thermal sensation and conmfort/discomfort were assessed using visual analog scales. The CbodyClocal combination evoked local cold sensation and whole-body thermal discomfort, while HbodyClocal induced local cold sensation but whole-body comfort. The CbodyHlocal combination induced local warm sensation and whole-body thermal comfort. The estimated dipole source regions associated with thermal comfort or discomfort included the right superior frontal gyrus, left medial frontal gyrus, left cingulate gyrus, left insula, right medial frontal gyrus, right middle temporal gyrus, right anterior cingulate gyrus, and right posterior cingulate gyrus. Even with the same local stimulus for Cbody and Hbody, distinct power perturbations across frequency bands were observed in different estimated source regions. These results suggest that thermal comfort and discomfort are associated with distinct spatiotemporal patterns of brain source activity.