The Dynamics of Memory Retrieval and Forgetting

描述(由申请者提供)：本研究的具体目的是：1)测试计算模型所做出的关于theta节律与记忆提取和记忆强度之间的关系的预测；2)进一步完善和发展这些模型。这些模型及其预测，如果得到证实，将与阿尔茨海默病、成瘾和创伤后应激障碍(PTSD)等疾病的临床治疗发展直接相关。在具体目标1下，我将在两个环境中为大鼠提供广泛的经验。定义这些环境的特征将包括围栏照明和行为奖励应急。我将记录大鼠在进行纯环境试验和混合环境试验时，海马区的定位细胞和内侧嗅觉皮质中的网格细胞的活动情况。在纯环境试验期间，环境特征将在整个试验过程中保持不变；我将使用这些试验来表征两个独立环境中所有细胞(即空间地图)的空间调整。在混合环境试验期间，环境特征将在每次试验期间多次在定义独立环境的环境特征之间切换。我将根据种群活动推断，在这些混合环境试验期间的每一个时刻，哪个空间地图都被激活。在实验1中，我将测试一个空间地图关闭而另一个空间地图取而代之的时刻是否不均匀地发生在正在进行的theta节奏的各个阶段。在实验2中，我将测试是否有可能诱导对空间地图的部分提取，从而按照我之前提出的模型预测的那样，改变替代空间地图的激活点。在实验3中，我将测试大鼠的行为与哪个空间地图被激活之间的对应关系，以测试这种操作是否可以作为改变行为的临床疗法。在实验4中，我将探索海马和内嗅觉重新映射的相对时间。在特定目标#2下，我将使用计算建模来支持在特定目标#1下描述的经验性工作。具体地说，我将使用产生预测的相同模型来模拟我将用来测试这些预测的任务。从这些模拟中，我将生成合成数据，我将在其上验证我将用来推断哪个空间地图在每个时刻处于活动状态的数据分析方法。这些模拟还将允许我开发刺激控制方案，用于特定目标#1的实验2，它将最可靠地产生部分提取。最强大的是，它们将允许我生成关于特定目标#1中描述的预测的边界条件的额外的可测试预测，从而激励我接下来的一系列实验。

DESCRIPTION (provided by applicant): The specific aims of the research proposed here are to 1) test predictions, made by computational models, regarding the relationship between theta rhythms and memory retrieval and memory strength; and 2) further refine and develop these models. These models and their predictions, if verified, carry direct relevance for the development of clinical therapies for disorders such as Alzheimer's disease, addiction, and post-traumatic stress disorder (PTSD). Under Specific Aim #1, I will provide rats with extensive experience in two environments. Defining features of these environments will include the enclosure lighting and the behavior-reward contingency. I will record the activity of place cells in the hippocampus and grid cells in the medial entorhinal cortex as the rats perform pure-environment trials and mixed-environment trials. During pure-environment trials, the environmental features will remain fixed throughout the trial; I will use these trials to characterize the spatial tunings of all of the cells (i.e., the spatial map) in the two separate environments. During mixed-environment trials, the environmental features will be flipped between those that define the separate environments multiple times during each trial. I will infer, based on the population activity, which spatial map is activated at each moment during these mixed-environment trials. In Experiment 1, I will test whether the moment at which one spatial map turns off and the other takes its place occurs non-uniformly over the phases of ongoing theta rhythms. In Experiment 2, I will test whether it is possible to induce the partial retrieval of a spatial map and thereby shift the point at which the alternate spatial map activates as was predicted by my previously proposed model. In Experiment 3, I will test the correspondence between the rat's behavior and which spatial map is activated to test whether such manipulations could serve as a clinical therapy to alter behavior. In Experiment 4, I will explore the relative timing of hippocampal and entorhinal remapping. Under Specific Aim #2, I will use computational modeling to support the empirical work described under Specific Aim #1. Specifically, I will use the same models that generated the predictions that I will address under Specific Aim #1 to simulate the task that I will use to test these predictions. From these simulations, I will generate synthetic data on which I will verify the data analysis methods that I will use to infer which spatial map is active at each moment. These simulations will also allow me to develop the stimulus control protocol, for use during Experiment 2 of Specific Aim #1, that will most reliably generate partial retrieval. Most powerfully, they will allow me to generate additional testable predictions regarding the boundary conditions of the predictions described under Specific Aim #1 and thereby motivate my next series of experiments.