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整个大脑中的活动支持的，信号在大脑的参与区域之间传递。事实上，有一个活跃的研究方向，被称为连接组学，试图在多个空间尺度上找到这样的连接。然而，找出哪些区域是相连的是不够的。相反，重要的是确定区域如何以及在什么方向上连接。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，有必要了解信号在空间和时间上的输入模式是如何在目标网络上处理的。这是一个庞大的科学项目，其中数学和建模可以在指导实验中发挥核心作用。本研究的目的是产生一个工作的主体，是在添加具有时序结构的输入到显示节奏结构的网络中所遇到的一般问题的代表。从这些例子中，这个项目的目标是寻找具有外部输入的神经元网络的一般原理。这种强迫网络远比研究得很充分的简单强迫振子现象复杂得多。该项目将支持两名研究生，并将在认知节律协作的背景下进行，这是一个由美国国家科学基金会支持的小组，由波士顿地区的二十多个实验室组成，研究大脑动力学和认知。该中心旨在促进其众多小组之间的合作，特别关注这些小组的研究生和博士后。该项目关注的是具有多个时间尺度的输入信号对具有多个时间尺度的神经元目标网络的影响。从这些现象在神经系统中表现出来的大量例子中，本研究集中在两个特别重要的生物学上。第一种是伽马和θ节律的相互作用，主要是在海马网络中，海马和新皮层的其他部分也携带着这种时间模式。第二种是体外实验和计算研究的顶叶皮层区域的节律；众所周知，顶叶皮层是连接的枢纽，接收来自许多其他区域的输入。所讨论的特定节奏作为刺激的后效而出现，并且已经通过计算显示可以改变网络对后期张力兴奋的反应。这项研究将提高对网络的理解，以更复杂的频谱特性显示这种输入节奏，比如来自其他大脑区域的输入。所涉及的网络既有兴奋性细胞，也有抑制性细胞，有时在目标网络中有多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.