Neuronal synchrony during anaesthesia - A thalamocortical model

TL;DR

This paper presents a thalamocortical model explaining how neuronal synchrony in theta and delta oscillations varies with anesthesia depth, affecting information coding by neuronal ensembles.

Contribution

It introduces a novel thalamocortical model capturing phase relationships and interactions of oscillations during anesthesia, aligning with experimental data.

Findings

Delta and theta activities are generated separately by thalamus and cortex.

Synchrony levels correlate with anesthesia depth, inhibiting or facilitating information coding.

Model results match experimental observations.

Abstract

There is growing evidence in favour of the temporal-coding hypothesis that temporal correlation of neuronal discharges may serve to bind distributed neuronal activity into unique representations and, in particular, that $\theta$ (3.5-7.5 Hz) and $\delta$ ($0.5<$3.5 Hz) oscillations facilitate information coding. The $\theta$ and $\delta$ rhythms are shown to be involved in various sleep stages, and during an{\ae}sthesia, and they undergo changes with the depth of an{\ae}sthesia. We introduce a thalamocortical model of interacting neuronal ensembles to describe phase relationships between $\theta$ and $\delta$ oscillations, especially during deep and light an{\ae}sthesia. Asymmetric and long range interactions among the thalamocortical neuronal oscillators are taken into account. The model results are compared with the experimental observations of Musizza et al. {\it J. Physiol. (London)} 2007 580:315-326. The $\delta$ and $\theta$ activities are found to be separately generated and are governed by the thalamus and cortex respectively. Changes in the degree of intra--ensemble and inter--ensemble synchrony imply that the neuronal ensembles inhibit information coding during deep an{\ae}sthesia and facilitate it during light an{\ae}sthesia.