magnetoencephalography

Magnetoencephalography (MEG) is presented as a brain-imaging method that maps electrical activity and makes changes in communication across the brain visible. In psychedelic research at Imperial College London, it helped researchers compare patterns of brain activity during normal waking consciousness with patterns after psilocybin. The resulting maps did not make a subjective experience directly observable; they offered a view of the brain’s changing organization while that experience unfolded, connecting reported effects with measurable changes in neural communication.

Use in Psychedelic Brain Research

The work took place in the laboratory of David Nutt at Imperial College London, where a team led by Robin Carhart-Harris had been studying the neural correlates of psychedelic experience since 2009. Researchers administered LSD and psilocybin to volunteers and used several scanning technologies, including functional magnetic resonance imaging and MEG, to observe changes in the brain. Together, these methods offered some of the first glimpses of physical processes associated with experiences such as hallucination and self-dissolution.

MEG had a particular role in tracking the brain’s internal communications. In a 2014 paper, the Imperial College team used it to map electrical activity during ordinary waking consciousness and after a psilocybin injection. The comparison rendered each network as a different color around a circular diagram. In the normal-state map, networks communicated mainly within their own boundaries, with comparatively few heavily used routes between them. This visual arrangement made the baseline pattern legible: specialized systems largely kept to themselves, and much of the traffic connecting them passed through a limited number of pathways.

The Psilocybin Maps

The map made after psilocybin showed a markedly different pattern. Thousands of new connections linked regions that, in normal waking consciousness, exchanged relatively little information. Rather than relying on a small number of major routes, communication appeared to spread across many more links between distant parts of the brain. The book likens the change to traffic leaving a few interstate highways for a dense web of smaller roads. The comparison describes not merely increased activity, but a redistribution of communication: formerly distinct networks became less separate and more globally interconnected.

This pattern accords with the broader account of psychedelic brain imaging in the book. Specialized systems, including the default mode network and the visual-processing system, became less integrated internally as the brain as a whole became more integrated through new connections. The maps therefore offered a way to examine the apparent paradox of local disorganization alongside wider communication. They supported a picture of reduced specialization and greater flexibility, rather than a simple claim that the entire brain either became more or less active.

Possible Connections to Experience

The significance of the maps lies partly in the kinds of experience that new connections might help explain. If memory and emotion systems communicate more directly with visual-processing systems, the contents of memory, wishes, fears, and feelings may influence what a person sees. The book associates this possibility with features of primary consciousness and with a heightened tendency to experience meanings or associations as immediate. Cross-system connections may also help account for synesthesia, in which information from one sense is experienced through another, such as colors as sounds or sounds as tactile sensations.

The same account offers a possible route from altered connectivity to hallucination. A memory can shape visual perception, or a familiar reflection can take on an unfamiliar, personally charged identity. New connections might also accompany a creative insight, a fresh perspective, or a changed meaning for something already familiar. These are proposed ways in which altered communication could affect mental life, not a claim that a scan can identify the meaning of any one person’s experience. The increase in entropy is described as permitting a broad range of mental states, some bizarre or senseless and others potentially imaginative or transformative.

What the Method Makes Visible

MEG’s contribution is thus both concrete and limited. It produces a map of electrical activity and allows researchers to compare patterns of communication under different conditions. The diagrams make a change in network organization visible: fewer dominant routes and more connections linking distant regions after psilocybin. They give neuroscientific form to the idea that a psychedelic state is not simply an intensified version of ordinary perception, but may involve a reorganization in how brain systems communicate.

The maps do not, by themselves, settle how that reorganization produces a particular thought, image, or therapeutic outcome. The book emphasizes that psychedelic effects are difficult to separate from the context in which a drug is administered, the presence of guides or therapists, and a volunteer’s expectations. Those challenges matter when interpreting brain-imaging results: a visible change in connectivity is evidence about the brain’s activity, not an isolated explanation of the experience as a whole. MEG therefore occupies an important middle ground in the account—linking subjective reports to physical patterns while leaving open the broader question of how neural activity, personal meaning, and the conditions of a session interact.