NEURAL BASIS OF INTERNAL REPRESENTATION OF PLACE

地点内部表征的神经基础

• 批准号: 6639373
• 负责人: BRUCE L MCNAUGHTON
• 金额: $ 34.09万
• 依托单位: UNIVERSITY OF ARIZONA
• 依托单位国家: 美国
• 财政年份: 1984
• 资助国家: 美国
• 起止时间: 1984-03-01 至 2005-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6639373
• 关键词: NMDA receptors; behavior test; behavioral /social science research tag; brain electrical activity; experimental brain lesion; hippocampus; laboratory rat; learning; memory; neural conduction; neural information processing; neurophysiology; space perception

DESCRIPTION (Adapted from Applicant's abstract): This proposal is intended to further our understanding of the internal dynamics of hippocampal information processing that may assist in the efficient storage and retrieval of sequence information. Among other things, the hippocampal formation is necessary for certain kinds of memory that have a temporal dimension, such as memory for episodes, serial order of places visited, routes to goals, and associative conditioning that bridges temporal gaps. Several theories suggest that the anatomical and physiological organization of the hippocampus may be particularly well suited to the encoding and storage of sequential relationships among events, and we have obtained evidence for the storage and retrieval of sequences of hippocampal neuronal ensemble activity. A sequence A-B-C can be learned by selectively strengthening synapses from A to B, and so forth; however there are two principal constraints. One is that the neural patterns to be sequentially associated must change rapidly relative to the time-constant of the associative mechanism (e.g., the NMDA receptor). Otherwise the network gets trapped in one state. For example, the sequence A-A-B-B0-C-C might get stuck but A-B0C would not. The other constraint is that, if items of the input sequence are repeated, then sequential (temporal) context information must be encoded or the prediction of the next item becomes ambiguous. Thus, in a sequence A-B-C-B-D, the two Bs must be encoded differently if C and D are to be retrieved correctly. The dynamics of hippocampal neural ensemble representations exhibit two properties that may serve to overcome these constraints. First, when an animal passes through the "place field" of a given pyramidal ('place') cell, the cell begins firing late in the theta rhythm cycle and the firing phase shifts progressively earlier as the rat runs through the field (a phenomenon known as "phase precession"). This means that a sliding window of the global sequence of place fields is replicated in a compressed form within each cycle, thus making the ensemble codes at the beginning and end of the theta cycle essentially uncorrelated. This could solve the first constraint i.e., rapid change of the code. A better understanding of the origin of the phase precession effect and the dynamics of information flow in relation to it must be reached, however, in order to verify this hypothesis. Second, the hippocampus has the property of being able to create completely different codes for the same spatial location, depending on behavioral and other contextual variables. It may thus also be able to orthogonalize place representations that occur as ambiguous elements of sequences, thereby solving the ambiguous sequence problem; but this needs to be determined. In addition, to understand the role of the hippocampus in both spatial and general episodic memory, it is necessary to achieve a better understanding of the factors that govern the spatial and temporal scales of hippocampal neuronal activity. The experiments described in this proposal address these issues.

描述（改编自申请人摘要）：本提案旨在 进一步了解海马信息的内部动力学 可能有助于有效存储和检索序列的处理 信息.除此之外，海马结构是必要的， 具有时间维度的某些类型的存储器，例如用于 情节，访问的地方的序列顺序，到达目标的路线，以及关联 弥补时间空白的条件反射一些理论认为， 海马体的解剖学和生理学组织可能 特别适合于序列的编码和存储 事件之间的关系，我们已经获得了证据的存储和 海马神经元整体活性序列的检索。的序列 A-B-C可以通过选择性地加强从A到B的突触来学习，等等。 然而，有两个主要的限制。一个是， 要顺序关联的模式必须相对于 关联机制的时间常数（例如，NMDA受体）。否则 网络被困在一个状态。例如，序列A-A-B-B 0-C-C 可能会卡住，但A-B 0 C不会。另一个限制是，如果 输入序列被重复，然后顺序（时间）上下文信息 必须被编码，否则下一项的预测变得模糊。因此在 序列A-B-C-B-D，如果C和D要 要正确检索。海马神经系统的动力学 表示具有两个特性，可以用来克服这些问题。 约束首先，当一个动物通过一个给定的“位置场”时， 在θ节律周期的晚期，细胞开始放电 并且当大鼠跑过 场（一种称为“相位进动”的现象）。这意味着， 位置字段的全局序列的窗口被复制在压缩的 形成在每个周期内，从而使合奏代码在开始和结束 基本上没有关联这可以解决第一个问题 约束即，快速修改代码。更好地了解起源 相位进动效应和信息流的动力学 然而，为了验证这一假设，必须达到这一点。二是 海马体有一种特性， 对于相同的空间位置，取决于行为和其他上下文 变量因此，它也能够正交化位置表示， 作为序列的歧义元素出现，从而解决了歧义 这是一个问题，但这需要确定。此外，为了了解 海马在空间和一般情景记忆中的作用， 为了更好地了解决定性因素， 海马神经元活动的时空尺度。实验 本提案中描述的内容解决了这些问题。