Dynamic Balance of Excitation and Inhibition in Human and Monkey Neocortex

TL;DR

This study demonstrates that excitation and inhibition are balanced in the neocortex of humans and monkeys across various states, with disruptions during seizures indicating potential links to pathological conditions.

Contribution

It provides evidence that balanced excitation and inhibition are fundamental features of normal neocortical activity in higher mammals, supported by multi-scale dynamics analysis.

Findings

Balanced excitation and inhibition are maintained across wake-sleep states.

Correlated fluctuations occur at multiple temporal scales.

Balance breaks down during seizures, indicating pathological disruption.

Abstract

Balance of excitation and inhibition is a fundamental feature of in vivo network activity and is important for its computations. However, its presence in the neocortex of higher mammals is not well established. We investigated the dynamics of excitation and inhibition using dense multielectrode recordings in humans and monkeys. We found that in all states of the wake-sleep cycle, excitatory and inhibitory ensembles are well balanced, and co-fluctuate with slight instantaneous deviations from perfect balance, mostly in slow-wave sleep. Remarkably, these correlated fluctuations are seen for many different temporal scales. The similarity of these computational features with a network model of self-generated balanced states suggests that such balanced activity is essentially generated by recurrent activity in the local network and is not due to external inputs. Finally, we find that this balance breaks down during seizures, where the temporal correlation of excitatory and inhibitory populations is disrupted. These results show that balanced activity is a feature of normal brain activity, and break down of the balance could be an important factor to define pathological states.