Qian Shaowen, Jiang Qingjun, Liu Kai, Li Bo, Li Min, Li Li, Yang Xiao, Yang Zhen, Sun Gang
Department of Medical Imaging, Jinan Military General Hospital, Shandong, PR China.
Department of Medical Imaging, Jinan Military General Hospital, Shandong, PR China.
Physiol Behav. 2014 Apr 10;128:99-107. doi: 10.1016/j.physbeh.2014.01.028. Epub 2014 Feb 14.
Environmental hyperthermia is a very common risk factor for many occupations, however, its potential influences on cerebral circulation remain obscure. In this study, 20 participants underwent two simulated environmental thermal conditions (50 °C/25 °C, 1 h), and their cerebral blood flows (CBFs) were quantified using a pseudo-continuous arterial spin labeling (ASL) MR imaging. During the experiment, the physiological parameters, including rectal temperature, arterial blood pressure and weight loss, heart rate and respiration rate, were recorded, and a visual analog scale (VAS) test was performed during both conditions to evaluate the psychological state including vigilance, anxiety, vigor, confidence, anger, nervousness, drowsiness, and loquacity. After scanning, a highly-demanding attentional task--the psychomotor vigilance test (PVT) was performed for behavioral performance evaluation. Compared with that during normothermic condition, the global CBF (gCBF) during hyperthermic condition showed a tendency of decrease, but no significant differences. Regional CBFs (rCBFs) were significantly altered mainly in the prefrontal cortex, somatosensory areas and limbic system. Physiological detection revealed significantly decreased diastolic pressure and systolic pressure and accelerated respiration rate. Furthermore, linear multivariate regression analysis showed that altered rCBFs in several regions could be predicted by physiological (systolic pressure, rectal temperature) and psychological (vigilance, drowsiness, nervousness, anger) changes. And PVT revealed significantly slower attentional reaction during hyperthermia, and the longer reaction time was correlated with the altered rCBF in the left dorsolateral prefrontal cortex (DLPFC). These findings suggested that during short-term hyperthermia gCBF might remain relatively stable under the integrated effect of physiological changes and cerebral auto-regulation, rather than decreased solely dependently on hyperthermia-induced physiological changes. Furthermore, altered regional blood distribution might be accounted for neural activity of thermal sensation and regulation, mood state and cognitive changes.
环境高温是许多职业中非常常见的风险因素，然而，其对脑循环的潜在影响仍不清楚。在本研究中，20名参与者经历了两种模拟环境热条件（50℃/25℃，1小时），并使用伪连续动脉自旋标记（ASL）磁共振成像对他们的脑血流量（CBF）进行了量化。实验期间，记录了包括直肠温度、动脉血压、体重减轻、心率和呼吸频率在内的生理参数，并在两种条件下进行了视觉模拟量表（VAS）测试，以评估包括警觉性、焦虑、活力、信心、愤怒、紧张、嗜睡和健谈在内的心理状态。扫描后，进行了一项要求很高的注意力任务——心理运动警觉性测试（PVT）以评估行为表现。与正常体温条件下相比，高温条件下的全脑CBF（gCBF）呈下降趋势，但无显著差异。局部CBF（rCBF）主要在前额叶皮层、体感区域和边缘系统有显著改变。生理检测显示舒张压和收缩压显著降低，呼吸频率加快。此外，线性多元回归分析表明，几个区域rCBF的改变可以通过生理（收缩压、直肠温度）和心理（警觉性、嗜睡、紧张、愤怒）变化来预测。PVT显示高温期间注意力反应明显减慢，且较长的反应时间与左侧背外侧前额叶皮层（DLPFC）中rCBF的改变相关。这些发现表明，在短期高温期间，在生理变化和脑自动调节的综合作用下，gCBF可能保持相对稳定，而不是仅依赖于高温诱导的生理变化而降低。此外，局部血液分布的改变可能是由热感觉和调节的神经活动、情绪状态和认知变化引起的。
