Sinha Rakesh Kumar
Department of Biomedical Instrumentation, Birla Institute of Technology, Mesra, Ranchi, Jharkhand-835215, India.
Biomed Environ Sci. 2009 Apr;22(2):141-50. doi: 10.1016/S0895-3988(09)60037-4.
To demonstrate changes in different frequencies of cerebral electrical activity or electroencephalogram (EEG) following exposure to high environmental heat in three different age groups of freely moving' rats.
Rats were divided into three groups (i) acute heat stress--subjected to a single exposure for four hours at 38 degrees C; (ii) chronic heat stress--exposed for 21 days daily for one hour at 38 degrees C, and (iii) handling control groups. The digital polygraphic sleep-EEG recordings were performed just after the heat exposure from acute stressed rats and on 22nd day from chronic stressed rats by simultaneous recording of cortical EEG, EOG (electrooculogram), and EMG (electromyogram). Further, power spectrum analyses were performed to analyze the effects of heat stress.
The frequency analysis of EEG signals following exposure to high environmental heat revealed that in all three age groups of rats, changes in higher frequency components (beta 2) were significant in all sleep-wake states following both acute and chronic heat stress conditions. After exposure to acute heat, significant changes in EEG frequencies with respect to their control groups were observed, which were reversed partly or fully in four hours of EEG recording. On the other hand, due to repetitive chronic exposure to hot environment, adaptive and long-term changes in EEG frequency patterns were observed.
The present study has exhibited that the cortical EEG is sensitive to environmental heat and alterations in EEG frequencies in different sleep-wake states due to heat stress can be differentiated efficiently by EEG power spectrum analysis.
在三组自由活动的不同年龄大鼠中，证明暴露于高温环境后不同频率的脑电活动或脑电图（EEG）的变化。
将大鼠分为三组：（i）急性热应激组——在38摄氏度下单次暴露4小时；（ii）慢性热应激组——每天在38摄氏度下暴露1小时，持续21天；（iii）处理对照组。对急性应激大鼠热暴露后以及慢性应激大鼠第22天时，通过同时记录皮质脑电图、眼电图（EOG）和肌电图（EMG）进行数字化多导睡眠脑电图记录。此外，进行功率谱分析以分析热应激的影响。
暴露于高温环境后的脑电图信号频率分析显示，在所有三个年龄组的大鼠中，急性和慢性热应激条件下，所有睡眠-觉醒状态下高频成分（β2）的变化均显著。急性热暴露后，观察到脑电图频率相对于其对照组有显著变化，在4小时的脑电图记录中部分或完全逆转。另一方面，由于长期反复暴露于热环境，观察到脑电图频率模式的适应性和长期变化。
本研究表明，皮质脑电图对环境热敏感，通过脑电图功率谱分析可以有效区分热应激导致的不同睡眠-觉醒状态下脑电图频率的变化。
