Aizawa Yuka, Harada Tokiko, Nakata Hiroki, Tsunakawa Mizuki, Sadato Norihiro, Nagashima Kei
Body Temperature and Fluid Laboratory, Faculty of Human Sciences, Waseda University, Tokorozawa, Japan.
Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
IBRO Rep. 2019 Jan 7;6:54-63. doi: 10.1016/j.ibror.2019.01.003. eCollection 2019 Jun.
The conscious perception of thermal stimuli is divided into two categories: thermal sensation (i.e., discriminative component) and pleasantness/unpleasantness (i.e., hedonic component). There have been very few studies which clearly dissociated the two components. The aim of the present study was 1) to identify brain regions involved in perception of thermal stimuli per se, dissociating those related to the two components, and additionally 2) to examine brain regions of the explicit evaluation processes for the two components. Sixteen participants received local thermal stimuli of either 41.5 °C or 18.0 °C during whole-body thermal stimuli of 47.0 °C, 32.0 °C, or 17.0 °C. The local stimuli were delivered to the right forearm with the Peltier device. The whole-body stimuli delivered through a water-perfusion suit was aimed to modulate thermal pleasantness/unpleasantness to the local stimulus. The local stimulation at the same temperature was conducted five times with 30-s intervals. Brain activation was assessed by functional magnetic resonance imaging (fMRI), and the participants were asked to report their ratings of thermal sensation and pleasantness/unpleasantness following the cessation of each local stimulus. Local thermal stimulation activated specific brain regions such as the anterior cingulate cortex, insula, and inferior parietal lobe, irrespective of the temperature of local and whole-body stimuli; however, no specific activation for hot or cold sensation was observed. Different brain regions were associated with pleasantness and unpleasantness; the caudate nucleus and frontal regions for pleasantness, and the medial frontal and anterior cingulate cortex for unpleasantness. In addition, the explicit evaluation process for the discriminative and hedonic components immediately following the cessation of local stimulus involved different brain regions; the medial prefrontal cortex extending to the anterior cingulate cortex, insula, middle frontal cortex, and parietal lobes during the explicit evaluation of thermal sensation, and the medial prefrontal cortex, posterior cingulate cortex, and inferior parietal lobes during that of pleasantness/unpleasantness.
热感觉（即辨别成分）和愉悦/不愉悦感（即享乐成分）。很少有研究能明确区分这两个成分。本研究的目的是：1）识别与热刺激本身感知相关的脑区，区分与这两个成分相关的脑区，此外2）检查对这两个成分进行明确评估过程的脑区。16名参与者在47.0°C、32.0°C或17.0°C的全身热刺激过程中接受41.5°C或18.0°C的局部热刺激。局部刺激通过珀尔帖装置施加到右前臂。通过水灌注服进行的全身刺激旨在调节对局部刺激的热愉悦/不愉悦感。在相同温度下进行五次局部刺激，间隔30秒。通过功能磁共振成像（fMRI）评估脑激活情况，并要求参与者在每次局部刺激停止后报告他们的热感觉和愉悦/不愉悦感评分。局部热刺激激活了特定的脑区，如前扣带回皮质、脑岛和顶下小叶，无论局部和全身刺激的温度如何；然而，未观察到对热或冷感觉的特异性激活。不同的脑区与愉悦感和不愉悦感相关；尾状核和额叶区域与愉悦感相关，而内侧额叶和前扣带回皮质与不愉悦感相关。此外，局部刺激停止后立即对辨别和享乐成分进行的明确评估过程涉及不同的脑区；在对热感觉进行明确评估期间，内侧前额叶皮质延伸至前扣带回皮质、脑岛、额中回皮质和顶叶，而在对愉悦/不愉悦感进行评估期间涉及内侧前额叶皮质、后扣带回皮质和顶下小叶。
