Lateral Entorhinal Cortex (LEC) and episodic memory: examining LEC's impact on pattern separation and neurogenesis

情景记忆是一个基本的认知过程。我们的情景记忆包括特定物体或人的细节，空间位置和上下文细节，使我们能够区分一个事件和另一个事件。情景记忆的一个关键特征是，它整合了事件的特征，以帮助指导未来的行为。例如，今天早上我们把车停在哪里的情景记忆会让我们在需要回家的时候准确地找到车。大脑中被称为海马体的区域受到损伤会导致无法形成新的情景记忆。我们自己最近的工作表明，侧内嗅皮层（LEC）向海马体的主要输入之一对于整合事件的特征也是必要的，这表明了LEC-海马体网络在情景记忆中的关键作用。然而，在这个网络中整合这些信息的电路机制是未知的。LEC输入海马的主要目标之一是齿状回（DG）子野。DG是大脑中为数不多的几个区域之一，在这个被称为神经发生的过程中，每天都会产生新生神经元。这些新生的神经元已经被证明对简单的记忆形式很重要，比如恐惧条件反射，特别是一个叫做模式分离的过程，它使我们能够区分相似的刺激。然而，这些新生神经元和模式分离在区分非常相似事件的不同情景记忆中的作用尚不清楚。作为关键的下一步，我们将测试假设，即神经发生介导海马中类似情景记忆的模式分离，并由LEC输入支持。我们将通过三个具体目标来验证这一假设的预测：目的1：确定新生神经元是否在需要整合情景记忆特征的测试中促进模式分离。目的2：确定LEC输入到DG中是否介导了需要整合EM特征的测试中新生神经元的数量和模式分离。目的3：确定在情景记忆特征整合测试中，神经发生是否影响海马位置细胞的模式分离。我们期待这项研究产生广泛的影响。情景记忆受饮食、运动、认知刺激等生活方式因素影响，情景记忆下降是阿尔茨海默病的首发症状。了解支持情景记忆的神经机制将为研究人员在整个生命周期中保持健康的认知功能以及那些试图开发记忆障碍治疗策略的研究人员提供特定的目标。我们还预计在减少记忆研究所需的实验动物数量方面也会产生影响。在过去的5年里，估计有43000只动物被用于研究物体识别，这是当前应用中所有行为任务的基础。这项拟议中的研究将检验丰富的环境如何能提高这些动物的记忆力。性能的提高将提高统计能力，这意味着研究这些类型的记忆需要更少的动物。考虑到所涉及的动物数量只有5%的研究界接受，可能意味着用于研究的动物减少了数千只。

Episodic memory is a fundamental cognitive process. Our episodic memories include details of specific objects or people, spatial locations and contextual details that allow us to differentiate between one event and another. A key feature of episodic memory is that it integrates the features of events to help guide future behaviour. For example, an episodic memory of where we parked our car this morning will allow us to accurately locate the car when we need to go home. Damage to an area of the brain called the hippocampus produces an inability to form new episodic memories. Our own recent work has shown that one of the main inputs to the hippocampus from lateral entorhinal cortex (LEC) is also necessary to integrate the features of an event pointing towards a key role for this LEC-hippocampus network in episodic memory. However, the circuit mechanisms within this network that integrate this information are unknown. One of the main targets for LEC input to hippocampus is the dentate gyrus (DG) subfield. DG is one of a small number of regions in the brain where newborn neurons are generated every day in a process called neurogenesis. These newborn neurons have been shown to be important for simple forms of memory such as fear conditioning, specifically for a process called pattern separation which allows us to discriminate between similar stimuli. However, the role of these newborn neurons and pattern separation in distinguishing between different episodic memories for very similar events is unknown. As a critical next step we will test the hypothesis that neurogenesis mediates pattern separation of similar episodic memories in the hippocampus supported by input from LEC. We will test predictions from this hypothesis through 3 specific aims:Aim 1: To determine whether newborn neurons facilitate pattern separation in tests requiring integration of the features of episodic memory.Aim 2: To determine whether LEC inputs to DG mediate the number of newborn neurons and pattern separation in tests requiring integration of EM features. Aim 3: To determine whether neurogenesis affects pattern separation in hippocampal place cells during tests requiring integration of episodic memory features.We anticipate wide reaching impact of this research. Episodic memory is affected by lifestyle factors such as diet, exercise and cognitive stimulation and decline in episodic memory is the first symptom of Alzheimer's disease. Understanding the neural mechanisms that support episodic memory will give specific targets to researchers interested in maintaining healthy cognitive function through the lifespan as well as those attempting to develop therapeutic strategies for disorders of memory. We also anticipate impact in the reduction of the number of laboratory animals needed in memory studies. In the last 5 years an estimated 43000 animals were used in studies of object recognition, the basis of all of the behavioural tasks in the current application. The proposed research will examine how enriched environments could improve memory performance in these animals. Improved performance would increase statistical power and mean that fewer animals would be needed to study these types of memory. Given the number of animals involved uptake by only 5% of the research community could mean thousands fewer animals being used in research.