The Cerebral Cortex Operates Through a Balance of Excitation and
Inhibition: Implications for Sleep, Memory, and Attention.
Yousheng Shu, Andrea Hasenstaub, Mavi Sanchez-Vives and David A. McCormick
Department of Neurobiology
Yale University School of Medicine
Introduction
The cerebral cortex exhibits multiple states of activity and excitability.
Some of these states slowly change, such as the transition between
sleep and waking. Others are more rapid, such as the operation of short-term
or "working" memory and shifts in attention. Although we have a relatively
clear understanding of how the slow changes in neuronal excitability may
come about with the sleep wake cycle (e.g. through the release of neuromodulatory
substances), it has been less clear how rapid changes of excitability may
be generated.
One hypothesis for the mechanisms underlying these rapid changes is through
network dynamics: the rapid turning on or off (activation or deactivation)
of groups of neurons. This type of persistent "reverberating" activity
within networks of cortical neurons has been hypothesized to underlie short
term or working memory (see next slide).
In this seminar, we examine the mechanisms by which local cortical
circuits may rapidly change states of activity through balanced recurrent
excitation and inhibition.
To be Specific, by examining the properties of the UP and DOWN states
of the slow oscillation in vitro, we sought to answer the following questions:
1. What are the cellular mechanisms for the generation of persistent
activity in the cortex?
2. How do synaptic barrages affect the excitability and responsiveness
of cortical cells?
3. How does the activation of afferent inputs turn persistent activity
on or off?
