睡眠对恐惧学习与树突棘可塑性影响研究

Learning and emotion memory circuity is one of the key areas for neuroscience research, in which fear conditioning is one of commonly used paradigm. Human studies have shown that sleep plays an important role in fear learning and related negative emotion, but the mechanisms are still remain elusive. This proposal will investigate the role of sleep in fear learning on the structural and functional synaptic plasticity of dendritic spines by awake, head-fixed two-photon imaging of transgenic mice expressing fluorescent protein or expressing genetic encoded calcium indicator by adeno-associated virus infection. Combining in vivo imaging and EEG/EMG recording, we will study the role of non-REM sleep and REM sleep for dendritic spine plasticity during memory consolidation phase after fear conditioning. These findings will shine light for the basic mechanisms and the possible pharmaceutical intervention by targeting specific sleep stage for fear memory consolidation in psychiatric disorders, such as PTSD and schizophrenia. The findings from this proposal will also lay ground work for future study on the possible role of sleep in fear extinction memory consolidation and the mechanisms involving fear learning-dependent dendritic spine plasticity.

情感和记忆的神经环路基础研究是神经科学的重点研究内容，习得性恐惧的神经环路是其中重点研究方向之一。临床研究显示，睡眠与恐惧及其相关负情绪有密切关系，但具体调控机制尚不明确。本课题将利用神经元荧光标记小鼠及腺相关病毒表达钙敏感荧光蛋白小鼠，利用清醒动物活体双光子显微成像技朮，以听觉条件性恐惧为模型，研究睡眠对恐惧依赖的树突棘结构及功能可塑性的调控作用。结合清醒动物脑电图及成像技朮，我们将研究非快动眼和快动眼睡眠在记忆巩固期间对树突棘在结构及功能可塑性的影响，以阐明睡眠对恐惧记忆巩固及神经环路结构的影响，并探索恐惧记忆巩固和恐惧依赖的树突棘可塑性新机制。本研究将探索习得性恐惧的神经可塑性机制，对情感和记忆的神经环路基础有重要指导作用；通过药物干预特定的睡眠阶段，以干扰恐惧记忆的巩固过程，达到对某些有习得性恐惧障碍的精神疾病，如创伤后应激障碍和精神分裂症等，作基础研究，以剖释相关神经环路。

使用经颅双光子显微镜，我们研究睡眠在依赖经验的树突棘消除小鼠额叶缔合皮层（Frontal Association）中的第5层锥体神经元中的作用。听觉提示恐惧学习（Auditory-cued fear conditioning）导致发育中的额叶缔合皮层迅速消除树突棘。睡眠剥夺或快动眼睡眠剥夺后，恐惧学习诱导的树突棘消除明显减少。睡眠或快动眼睡眠剥夺也阻止了恐惧学习诱导的条件听觉刺激引起的第5层锥体神经元活动的减少。此外，我们观察到与其他脑部状态相比，快动眼睡眠期间额叶缔合皮层的树突钙峰值(calcium spike activity)显着增加。特别是在快动眼睡眠期间，使用NMDA受体拮抗剂，MK-801另树突状钙尖峰的阻断，阻止了恐惧学习诱导的额叶缔合皮层中树突棘的消除。综上所述，这些发现揭示了快动眼睡眠在依赖经验的突触连接消除和皮层神经元活动减少中的重要作用。