Oscillatory Models of Short-Term Memory

9723466里斯曼这个项目的长期目标是了解短期记忆的网络和细胞基础，短期记忆是一种记忆类型，用于记忆电话号码等项目的简短列表。对人类进行的心理物理测试表明，短期记忆中最多只能存储7个项目。这项拟议的研究将扩展之前的理论工作，展示单个大脑网络如何使用多路复用方案同时保持7个记忆活跃。这一方案与对大脑振荡的生理观察密切相关；多路传输是通过时钟机制实现的，这在大脑记录中是明显的嵌套振荡，其中约7伽马(20-80赫兹)振荡发生在单个θ(4-10赫兹)周期中。在连续的伽马周期中，存储器变得连续活跃。对人类记忆的心理物理分析提供了丰富的量化数据集。这项拟议工作的目标是开发一种更详细的生理模型来正确预测这一数据。第一个具体目标是提供一个特定的模型，说明在识别记忆测试期间如何扫描记忆。计算机模拟方法将被用来以一种生理学上可信的方式对大脑网络进行建模。第二个目的是理解卡瓦纳观察到的一个令人惊讶的恒定：扫描一段记忆所需的时间和可以保存的记忆数量都会随着记忆的复杂程度而变化；然而，两者的乘积似乎是一个普遍的常量。第三个目标是了解是否存在限制伽马振荡速度的基本网络限制；如果它们更快，可以容纳更多的内存，但伽马不能更快可能有原因。与前两个目标相关的初步结果表明，随着存储记忆数量的增加，theta振荡频率可能会降低。此外，伽马频率可能随着存储物品的复杂性的增加而降低。这些都是重要的发现，因为它们提供了一种将短期记忆的易操作方面与大脑信号联系起来的方法，而且它们非常容易测试。作为这项提案的第四个目标，将启动合作努力来检验这些预测。

9723466 Lisman The long-term goal of this project is to understand the network and cellular basis of short-term memory, the type of memory used in remembering brief lists of items such as a phone number. Psychophysical tests on humans have shown that there is a limit of about 7 items that can be stored in short-term memory. The proposed research will extend previous theoretical work showing how a single brain network can keep 7 memories active at the same time using a multiplexing scheme. This scheme is closely tied to physiological observations on brain oscillations; multiplexing is achieved by a clocking mechanism, which is apparent in brain recordings as nested oscillations in which about 7 gamma (20-80Hz) oscillations occur within a single theta (4-10Hz) cycle. Memories become serially active in sequential gamma cycles. The psychophysical analysis of human memory provides a rich quantitative data set. The goal of the proposed work is to a develop a more detailed physiological model that correctly predicts this data. The first specific aim is to provide a specific model of how memories are scanned during a recognition memory test. Computer simulation methods will be used to model brain networks in a physiologically plausible way. The second aim is to understand a surprising constancy observed by Cavanagh: the time required to scan a memory and the number of memories that can be held both vary with the complexity of the memory; however the product of the two appears to be a universal constant. The third aim is to understand whether there are fundamental network constraints that limit how fast gamma oscillations can be; if they were faster, more memories could be held, but there may be reasons why gamma cannot be faster. Preliminary results related to the first two aims indicate that theta oscillation frequency may decrease as the number of stored memories increases. Furthermore, gamma frequency may decrease as the complexity of stored items increases. These are important findings because they provide a way of relating easily manipulatable aspects of short term memory to brain signals and because they are very testable. As the fourth goal of this proposal, collaborative efforts will be initiated to test these predictions.