Remote effects of focal hippocampal seizures on neocortical function

项目摘要/摘要 癫痫发作对神经系统功能既有局部影响，也有远程影响。颞叶癫痫是一种常见的 和衰弱的神经障碍，其特征是边缘结构引起的局灶性癫痫，包括 海马体。有趣的是，局灶性颞叶癫痫发作经常导致功能缺陷，如受损 意识，这不是单单由局部海马区损伤引起的。人局灶性颞叶 意识受损的癫痫发作在脑电(EEG)上表现为慢波并降低 大脑血流在远离海马体的新皮质。局灶性癫痫发作的机制 在海马区，导致新皮质功能受抑的原因尚不清楚。我们之前在老鼠身上所做的工作 局灶性边缘惊厥的模型再现了人类的发现，并表明皮质下减少 在癫痫发作期间，唤醒会导致意识受损。重要的是，皮质下觉醒的神经刺激 系统能够恢复癫痫发作期间的皮质功能和行为反应，为 在人类癫痫中恢复觉醒。因此，我们的中心假设是局灶性边缘癫痫发作减少 皮质下觉醒，引起皮质慢波和意识受损。然而，最根本的是 这些变化的机制尚未确定。我们最近开发了一种新型的清醒头部固定器 局灶性边缘惊厥的小鼠模型，为研究网络、神经递质提供了独特的机会 以及与行为有关的神经机制。我们发现，两者都增加了抑制作用，并降低了 在边缘癫痫发作中，兴奋可能与抑制的皮质下觉醒平行。此外，情绪低落 多个神经递质系统的觉醒可能导致皮质功能受损。我们现在计划 利用清醒小鼠模型的优势，采用包括高场fMRI在内的技术，从基因上 编码荧光神经递质传感器、光遗传学、单细胞电生理学和行为学 测试以充分研究惊厥中觉醒受损的机制。因此，我们的目标是第一 在清醒小鼠模型中研究局灶性边缘惊厥中觉醒受损的网络机制。 我们将通过功能磁共振成像绘制皮质和皮质下网络图，然后进行直接电生理记录， 进行刺激和断开实验，以识别关键网络节点。第二，我们将分析 皮质功能受抑时神经递质的变化。我们将使用基因编码的荧光指示器 和光遗传学来确定抑制增加和兴奋减少在抑郁症中的作用 皮质下唤醒；并将调查哪些唤醒神经递质与皮质功能受损有关 和行为。第三，我们将把单个神经元的活动与局灶性边缘癫痫发作的行为联系起来，使用 已鉴定的皮质下觉醒神经元的细胞旁记录和皮质神经元的全细胞记录。 觉醒模型中跨这些级别的信息集成将具有重要的翻译价值 指导开发新的治疗方法，目的是在癫痫发作期间和之后恢复意识。

PROJECT SUMMARY / ABSTRACT Seizures have both local and remote effects on nervous system function. Temporal lobe epilepsy is a common and debilitating neurological disorder, characterized by focal seizures arising from limbic structures, including the hippocampus. Interestingly, focal temporal lobe seizures often cause functional deficits such as impaired consciousness, which is not expected from local hippocampal impairment alone. Human focal temporal lobe seizures with impaired consciousness show slow waves on electro-encephalography (EEG) and decreased cerebral blood flow in the neocortex, distant from the hippocampus. The mechanisms by which focal seizures in the hippocampus cause depressed function in the neocortex are not known. Our previous work in a rat model with focal limbic seizures reproduced the human findings and suggested that decreased subcortical arousal produces impaired consciousness during seizures. Importantly, neurostimulation of subcortical arousal systems was capable of restoring cortical function and behavioral responses during seizures, offering hope for restored arousal in human epilepsy. Therefore, our central hypothesis is that focal limbic seizures decrease subcortical arousal, causing cortical slow waves and impaired consciousness. However, the fundamental mechanisms of these changes have not been determined. We recently developed a novel awake head-fixed mouse model of focal limbic seizures, providing unique opportunities to investigate network, neurotransmitter and neuronal mechanisms in relation to behavior. We found that both increased inhibition and decreased excitation may contribute in parallel to depressed subcortical arousal in limbic seizures. In addition, depressed arousal in multiple neurotransmitter systems may contribute to impaired cortical function. We now plan to capitalize on strengths of the awake mouse model to employ techniques including high field fMRI, genetically encoded fluorescent neurotransmitter sensors, optogenetics, single cell electrophysiology and behavioral testing to fully investigate the mechanisms of impaired arousal in seizures. Therefore, our aims are to first investigate the network mechanisms of impaired arousal in focal limbic seizures in the awake mouse model. We will map cortical and subcortical networks by fMRI, followed by direct electrophysiological recordings, stimulation and disconnection experiments to identify key network nodes. Second, we will analyze the neurotransmitter changes in depressed cortical function. We will use genetically encoded fluorescent indicators and optogenetics to determine the roles of increased inhibition and decreased excitation in depressed subcortical arousal; and will investigate which arousal neurotransmitters contribute to impaired cortical function and behavior. Third, we will relate the activity of single neurons to behavior in focal limbic seizures, using juxtacellular recordings of identified subcortical arousal neurons and whole cell recordings of cortical neurons. The integration of information across these levels in the awake model will have important translational value to guide development of new treatments aimed at restoring consciousness during and following seizures.