Modular dynamics of conscious and unconscious states in marmoset cortex

Using fMRI in awake and anesthetized marmosets, the study shows that the anesthetic isoflurane weakens functional brain networks, making them more fragmented and more closely resembling anatomical structure. In contrast, wakefulness is characterized by coordinated network reconfiguration and distinct subnetworks. The authors argue that consciousness emerges from the dynamics of functional brain networks and that anesthetics reduce these dynamics by impairing synaptic transmission.

Study at a glance

Abstract

General anesthetics are routinely used to induce unconsciousness. While much is known about their effects on receptor function and the activity of individual neurons, much less is known about how these local effects are manifest at the level of largescale, distributed brain networks. Using functional magnetic resonance imaging (fMRI) with the common marmoset (Callithrix jacchus) we investigated the effects of the anaesthetic isoflurane on functional brain networks and their temporal dynamics, comparing network measures during wakeful rest and induced unconsciousness. The anaesthetic condition was characterised by weak functional networks that were more similar to anatomical structure and more fragmented than during wakeful rest. Conversely, the awake condition was characterised by coordinated network reconfiguration and more distinct subnetwork composition. Our findings are consistent with the view that consciousness is an emergent property of the dynamics of functional brain networks, and that anaesthetics impoverish these dynamics by reducing the efficacy of synaptic transmission.