延长觉醒对前额叶皮层重激活的影响及机制研究

Prolonged wakefulness (e.g. insomnia and sleep deprivation), which is commonplace in modern culture, often leads to impairment in memory. Reactivation of memory traces in neocortex underlies memory consolidation. However, it is still not known whether the impairment in memory caused by prolonged wakefulness is due to an insufficient reactivation. Prefrontal cortex is an important area involved in learning and memory, and shows reactivation following learning. Also, this area is most sensitive to sleep loss relative to other cortical regions. Therefore, we will first investigate the influence of prolonged wakefulness on the reactivation in prefrontal cortex in this project, and observe the relationship between changes in reactivation and memory. Then, the mechanisms underlying the alterations in reactivation will be studied. At last, we will examine whether activation of arousal system could counteract the effects of prolonged wakefulness on reactivation and memory To achieve the above study, a variety of electrophysiological recordings in vivo will be applied, such as multi-channel recording, EEG and EMG, as well as other methods including behavioral test, morphological method and optogenetic technology. We expect to find out the changes in reactivation in neocortex during prolonged wakefulness, and thus clarify the mechanism of the impairment in memory at the level of neural network. These findings will provide more evidence for better understanding the neural substrates of impairment in memory during prolonged wakefulness.

以失眠和睡眠剥夺为代表的觉醒延长是现代社会的常见现象。在延长觉醒状态下人们往往出现记忆能力下降。学习后大脑皮层的重激活是记忆巩固的重要环节，但是延长觉醒所引起的记忆能力下降是否与大脑皮层重激活有关，目前并不清楚。前额叶皮层是参与学习记忆的重要脑区，在学习后会表现出明显的重激活现象，并且前额叶皮层的活动和功能对睡眠减少尤为敏感。因此本项目拟选择前额叶皮层为研究对象，采用在体电生理、行为学、形态学及光遗传学等技术，进一步观察延长觉醒过程中前额叶皮层神经网络重激活的变化，及其与记忆能力下降的相关性，初步探讨重激活变化的机制，并观察延长觉醒条件下强化促觉醒系统对重激活及学习记忆行为的影响。以期通过阐明与学习记忆密切相关的皮层重激活在延长觉醒期间的变化情况，为深入理解延长觉醒引起的学习记忆能力下降提供新的思路。

延长觉醒往往引起学习记忆能力下降，而其机制尚不清楚。在学习任务后，任务相关的神经元通过重激活对记忆进行巩固，而海马被认为是促使前额叶皮层等新皮层发生重激活的脑区。海马神经元上的离子型谷氨酸受体对于神经元之间信息传递、突触可塑性及学习后重激活等具有重要作用。在延长觉醒条件下，细胞膜上的离子型谷氨酸受体是否会发生变化，进而影响重激活现象及学习记忆行为，目前并不清楚。本项目研究发现大鼠延长觉醒4小时后，海马AMPA受体亚基GluA1、GluA2和GluA3及NMDA受体亚基GluN1、GluN2A和GluN2B的膜蛋白水平均显著降低；延长觉醒8小时后，海马AMPA受体GluA1亚基和NMDA受体GluN2A亚基的膜蛋白水平显著降低，而AMPA受体GluA2、GluA3亚基及NMDA受体GluN1和GluN2B亚基的膜蛋白水平显著增高。此外，延长觉醒4小时后，大鼠内嗅皮层AMPA受体GluA1亚基及NMDA受体GluN1、GluN2B亚基膜蛋白水平显著降低，AMPA受体GluA2和GluA3亚基膜蛋白水平显著增高，而NMDA受体GluN2A亚基膜蛋白水平没有显著变化。以上数据提示短期延长觉醒后，海马和内嗅皮层细胞膜上的离子型谷氨酸受体构型可能发生变化，进而影响学习后的重激活。进一步行为学实验显示，大鼠短期延长觉醒后在Morris水迷宫中表现出的空间参考记忆能力及在T-迷宫交替选择任务中表现出的空间工作记忆能力均相应下降。这些结果将为深入理解延长觉醒引起的学习记忆能力下降提供新的线索。