高温诱发人脑脑力疲劳的功能磁共振研究

Passive hyperthermia induces human brain fatigue:an fMRI study

目的采用静息态分数低频振幅(fractional amplitude of low frequency fluctuations,fALFF)技术结合精神运动警觉性实验(psychomotor vigilance task,PVT),探讨高温诱发人脑脑力疲劳的神经活动变化及意义。方法 20名被试按随机交叉顺序先进行生理参数(心率、呼吸率、血压、直肠温度)测量,再进行PVT测试,之后在高温(50℃)与常温(25℃)下暴露1h,并采集功能磁共振(functional magnetic resonance imaging,fMRI)数据,扫描结束后继续监测生理数据,待恢复到正常时再次进行PVT测试。fMRI数据采用fALFF分析,分别对其进行配对t检验。并对fALFF有显著变化的区域与PVT测试反应时做相关分析。结果行为学结果显示高温组实验后的PVT测试反应时较常温组显著延长。fALFF分析显示双侧丘脑、右尾状核、左壳核、左侧岛叶、左侧海马回等脑区fALFF值显著增高而双侧额中回、左侧额上回、右侧扣带回显著降低,其中右侧额中回、右侧扣带回与热暴露后的组间PVT反应时差值显著相关。结论高温后PVT测试反应时的增加,反映了高温诱发人脑脑力疲劳现象的存在,而静息态成像模式变化,进一步揭示了高温下人脑脑力疲劳神经学基础。

Objective To explore the neural activity alterations and mechanisms of brain fatigue induced by passive hyperthermia using resting state fractional amplitude of low frequency fluctuations （fALFF） combined with psychomotor vigilance task test.Methods Twenty participants experienced a hyperthermic condition （50℃） and a normal condition （25℃） for 1 hour in a random cross over design.Before heat exposure,physiological parameters of each participant were measured,including heat rate,respiration rate,blood pressure,rectal temperature.After hyperthermia exposure,resting state fMRI scans were collected,and after scanning,a psychomotor vigilance task test was performed while the physiological parameter returned to normal level.Paired t test was used to explore brain regions with significant altered fALFF.And furthermore,correlation analysis was performed between significant alteration of fALFF and reaction time in PVT test.Result Behavioral result showed that reaction time in pre-heat PVT test was significant longer than that in post-heat PVT test.Significant increased fALFFs were found in regions including bilateral thalamus,right caudate nucleus,left putamen,left insula,and left hippocampus,while,decreased fALFF were found in bilateral middle frontal gyrus,left superior frontal gyri,and left cingulate gyri.The alterations of fALFF in right middle frontal gyri and right cingulate gyri were significant correlated with the between-group reaction time alterations in PVT test after heat exposure.Conclusion The slower reaction time in post-heat PVT test may indicate hyperthermia-induced brain fatigue,while the alteration of resting-state fMRI further revealed the potential neural mechanism of brain fatigue during hyperthermia.