The multimodal Ganzfeld-induced altered state of consciousness induces decreased thalamo-cortical coupling.

An altered state of consciousness (ASC) induced by non-pharmacological Ganzfeld stimulation—where participants are exposed to intense, homogeneous visual and auditory input—progressively decouples the thalamus from the cortex, as measured by fMRI. This decoupling contrasts with psychedelic-induced ASCs, which typically show increased thalamo-cortical coupling. The Ganzfeld ASC also increased eigenvector centrality in core regions of the default mode network (DMN), opposite to the reduced DMN activity seen with psychedelics. These findings suggest an imbalance between sensory bottom-up and internally generated top-down signaling.

Study at a glance

Abstract

Different pharmacologic agents have been used to investigate the neuronal underpinnings of alterations in consciousness states, such as psychedelic substances. Special attention has been drawn to the role of thalamic filtering of cortical input. Here, we investigate the neuronal mechanisms underlying an altered state of consciousness (ASC) induced by a non-pharmacological procedure. During fMRI scanning, N = 19 human participants were exposed to multimodal Ganzfeld stimulation, a technique of perceptual deprivation where participants are exposed to intense, unstructured, homogenous visual and auditory stimulation. Compared to pre- and post-resting-state scans, the Ganzfeld data displayed a progressive decoupling of the thalamus from the cortex. Furthermore, the Ganzfeld-induced ASC was characterized by increased eigenvector centrality in core regions of the default mode network (DMN). Together, these findings can be interpreted as an imbalance of sensory bottom-up signaling and internally-generated top-down signaling. This imbalance is antithetical to psychedelic-induced ASCs, where increased thalamo-cortical coupling and reduced DMN activity were observed.