Interaction of Time Scales in Forced Rhythmic Networks of Neurons

现在人们普遍认为，认知功能是由分散在大脑各处的活动支持的，信号在大脑的参与区域之间传递。事实上，有一个被称为连接学的活跃研究方向，它试图在多个空间尺度上找到这样的联系。然而，仅仅找到联系在一起的区域是不够的。相反，重要的是确定各地区如何以及朝什么方向连接。作为神经计算过程的一部分，信号是如何传递和作用的？为了理解这种神经计算，有必要理解目标网络如何处理空间和时间上的信号输入模式。这是一个庞大的科学计划，数学和建模可以在指导实验中发挥核心作用。这项研究的目的是产生一系列工作，代表在将具有时序结构的输入添加到表现出节奏结构的网络中所遇到的一般问题。从这样的一系列例子中，这个项目的一个目标是寻找关于具有外部输入的神经元网络的一般原理。这样的受迫网络远比人们熟知的简单受迫振子现象复杂得多。这个项目将支持两名研究生，并将在认知节奏合作的背景下进行，这是一个由NSF支持的小组，由波士顿地区的二十多个实验室(主要是研究大脑动力学和认知的实验室)组成。儿童权利委员会旨在促进其众多群体之间的合作，特别关注这些群体的研究生和博士后。该项目关注具有多个时间尺度的输入信号对同样具有多个时间尺度的神经元的目标网络的影响。从神经系统中出现的大量这些现象的例子中，这项研究集中在两个特别具有生物学重要性的例子上。第一个是伽马和西塔节律的相互作用，主要是在海马体网络中，来自海马体其他部分和新大脑皮层的输入也带有这种时间模式。第二个是关于在体外通过实验和计算研究的顶叶皮质区域的节律；众所周知，顶叶皮质是连接的中心，来自许多其他区域的输入。所讨论的特定节律作为刺激的后效而出现，并已通过计算表明改变了网络对后来的紧张性兴奋的反应。这项研究将提高对显示这种具有更复杂光谱特性的输入节奏的网络的影响的理解，例如来自其他大脑区域的输入。涉及的网络既有兴奋性细胞，也有抑制性细胞，有时在目标网络中，不止一种抑制性细胞产生多个时间尺度。

It is now well accepted that cognitive functions are supported by activity dispersed throughout the brain, and that signals are passed among participating regions of the brain. Indeed, there is an active direction of study, known as connectomics, that seeks to find such connections on multiple spatial scales. It is not sufficient, however, to find what regions are connected. Rather it is important to determine how and in what directions regions are connected. How are signals conveyed and acted upon as part of a neural computational process? To understand such neural computations, it is necessary to understand how input patterns of signals in space and time are processed at the target network. This is a huge scientific program in which mathematics and modeling can play a central role in guiding experiments. The aim of this research is to produce a body of work that is representative of the general issues that are encountered in adding input that has timing structure to networks exhibiting rhythmic structure. From such a body of examples, a goal of this project is to search for general principles about networks of neurons with external input. Such forced networks are far more complex than the well-studied phenomena of simple forced oscillators. This project will support two graduate students and will be carried out within the context of the Cognitive Rhythms Collaborative, a NSF-supported group of more than two dozen labs (mostly) in the Boston area working on brain dynamics and cognition. The CRC is designed to facilitate collaborations among its many groups, with special attention to the graduate students and postdocs of these groups. This project is concerned with the effects of input signals with multiple time scales on target networks of neurons that also have multiple time scales. From the huge number of examples of these phenomena manifest in the nervous system, this research is focused on two of particular biological importance. The first is the interaction of gamma and theta rhythms, mainly in hippocampal networks, with inputs from other parts of the hippocampus and neocortex also carrying such temporal patterns. The second concerns a rhythm that has been experimentally and computationally investigated in a region of parietal cortex in vitro; parietal cortices are known to be hubs of connections, with inputs from many other areas. The particular rhythm in question arises as an after-effect of stimulation, and has been shown computationally to change the network response to later tonic excitation. This research will improve understanding of the effect on a network displaying this rhythm of input with more complex spectral properties, such as inputs from other brain regions. The networks involved have both excitatory and inhibitory cells, sometimes with more than one kind of inhibitory cell producing multiple time scales in the target network.