皮层下促觉醒脑区支配的内侧前额叶皮层神经回路活动及处理信息的特征研究

The prefrontal cortex (PFC), especially the medial PFC (mPFC), receiving abundant projections from subcortical arousal systems, is the most evolved brain regions highly associated with the level of wakefulness and plays a critical role in many higher cognitive functions, such as working memory and attention. A line of evidence support the notion that in concert with hippoampus, the mPFC is the major input source of hippocmapus in the establishement of short-term memory in wakfulness. Specially, the coupled communication of neural circuits between mPFC and hippocampus may be the key for working memory performance. Our previous results have demonstrated that application of arousal-promoting neuropeptide orexins could excite the mPFC neurons in vitro, while little is known about the characteristics and significance of arousal systems-innervating neural circuits in mPFC across sleep and wakefulness states in vivo. In this project, we will first investigate the characteristics of these neural circuits dominated by subcortical arousal systems, especially, orexinergic and noradrenergic afferents in sleep and wakefulness cycle. Then the activity of these neural circuits and different process of visual information as well as that of working memory performance will be recorded. And the relationship between activity of these neural circuits and corresponding changes of visual information processed as well as that of working memory performace during prolonged wakefulness will be analyzed eventually. Multiple recordings including in vivo mult-channel recordings, EEG recordings and extracellular recordings will be used frequently in our project, as well as other methods including optogenetic technology, histochemical stainning and behavioral tests, if any possible. Our hypothesis is that the arousal system-innervating neural circuits of mPFC will be firing fast during wakefulness and cease firing in sleep, which will be critically for the coding, recall informaion and short-term memory occuring only in the wakefulness. And due to the decline of responsive of mPFC neurons to excitatory afferents from subcortical arousal systems, prolonged wakefuless will result in the reduction of activity of these neural circuits, which will decrease the efficiency of processing information and damage the working memory performance. We expect to clarify the relationship between the activity of arousal systems-innervating neural circuits in mPFC and processing information, which will provide more evidence for better understanding the neural substrates of learning and memory as well as a theoretical basis for the treatment of cognitive impairment in prolonged wakefulness.

内侧前额叶皮层是与脑认知功能和觉醒水平高度相关的脑区，接受大量皮层下觉醒系统纤维的兴奋性输入，是觉醒期海马短期记忆的主要信息来源。最新研究表明，内侧前额叶皮层神经回路与海马神经回路间振荡活动的偶联是学习和记忆形成的功能基础。在前期研究外侧下丘脑促醒肽orexins对前额叶皮层神经元活动影响的基础上，本研究拟采用在体电生理、光遗传学、神经药理学、微透析、免疫组化技术和分子生物学技术，在体观察睡眠觉醒周期中，皮层下促觉醒脑区支配的内侧前额叶皮层神经元所构成的神经回路在睡眠觉醒周期中的活动特征，以及与信息处理的相关性；觉醒系统不同活动水平下，该神经回路活动的变化以及信息处理和学习记忆行为的改变。以期通过对觉醒系统支配的内侧前额叶皮层神经回路，参与信息获得、编码、短时储存及提取等觉醒相关的学习记忆活动关系的阐述，为理解大脑皮层认知功能的神经生物学基础以及持续觉醒时认知功能受损的治疗提供理论依据。

内侧前额叶皮层是与脑认知功能和觉醒水平高度相关的脑区，接受大量皮层下觉醒系统纤维的兴奋性输入，是觉醒期海马短期记忆的主要信息来源。本项目主要围绕受皮层下觉醒纤维支配的内侧前额叶皮层神经回路及参与信息处理不同阶段的神经元活动特征，及不同脑状态下，神经回路的活动变化与学习记忆间的行为关系进行了探讨。.采用束路追踪技术，本研究发现外侧下丘脑区及orexin神经元向内侧前额叶皮层发出直接的纤维投射，其中，阳性纤维广泛分布于I~VI层，位于内侧前额叶皮层AC亚区的阳性神经元数目显著多于PL和IL亚区，且三个亚区都有orexin受体1和受体2的表达，主要分布于II/III、V层。同时，内侧前额叶皮层PL区的神经元叶直接发出投射至orexin神经元。在体多通道记录实验结果显示，微注射orexin受体1拮抗剂显著抑制前额叶皮层锥体神经元放电和gamma振荡活动，但delta，theta，beta活动并无明显改变。光刺激外侧下丘脑orexin神经元，大部分前额叶皮层神经元放电频率增加，gamma振荡活动增加显著。提示，在自由清醒动物中，內源性释放的orexin能够通过受体1增加内侧前额叶皮层神经元的兴奋性和gamma振荡活动。此外，T迷宫实验初步提示，内侧前额叶皮层不同神经元参与信息的编码、贮存和重提取的不同过程。.前额叶皮层对持续觉醒产生的疲劳尤为敏感。本实验结果发现，延长觉醒4h后，谷氨酸AMPA和NMDA受体亚基总蛋白水平未发生明显，但受体亚基相应的膜蛋白与总蛋白的比例发生变化，提示短期延长觉醒主要影响亚基的转运，而对其基本表达无影响。8h延长觉醒后，AMPA受体中的Glu3亚基总蛋白显著增加，NMDA受体亚基GluN1膜表达降低，GluN2B膜表达增加，表明，延长觉醒主要通过影响翻译后的蛋白转运，影响NMDA受体的亚基膜表达水平。.通过对觉醒纤维与内侧前额叶皮层神经元活动和功能联系的阐述，不同觉醒水平状态皮层神经递质受体变化的探讨，为理解脑认知功能的神经生物学基础及持续觉醒时认知功能受损的治疗提供实验依据。