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Can LSD Help Us Understand the Mind–Brain Relationship?

Michael Egnor

In a fascinating article in The Guardian, “Acid test: scientists show how LSD opens doors of perception,” science editor Ian Sample discusses recent research on the mechanism by which LSD alters the brain and the mind. He begins by quoting Aldous Huxley (1894–1963) who noted that LSD “lowers the efficiency of the brain as an instrument for focusing the mind on the problems of life.” Remarkably, recent work in neuroscience supports Huxley’s view.

The research, conducted at Cornell University, confirms what has been called the Rebus model of psychedelics. Rebus is a rough acronym for “relaxed beliefs under psychedelics”; the model proposes that the brain is essentially a prediction engine for daily life. In this model, the brain processes information from the senses to help us understand the world efficiently. In doing so, it must take shortcuts and make predictions to enable quick perceptions and efficient responses. Psychedelic drugs suppress the ability of the brain to streamline perception and understanding. As the researchers put it, “Our findings provide support for a fundamental theory of the mechanism of action of psychedelics by showing that LSD flattens the brain’s energy landscape, allowing for more facile and frequent state transitions and more temporally diverse brain activity.”

Flattening the Landscape

The Cornell researchers used functional magnetic resonance imaging (fMRI) to study the brains of people on LSD or on a placebo (= the control group). While using LSD, the brains of volunteers showed less high-level processing and more activity related to more rudimentary sensation. One of the investigators described the effect as flattening the landscape over which the brain can roam — the drug makes it easier for the mind to transcend mundane perceptual habits and see the world in greater detail. Thus they enabled people to break out of repetitive and ruminative thought.

This work, whatever its other merits, lends credence to an understanding of the mind–brain relationship that goes back centuries. It was stated perhaps most clearly by Oxford philosopher Ferdinand Schiller in 1891 when he proposed that

… matter is not what produces consciousness but what limited and confines its intensity within certain limits … This explanation admits the connection of matter and consciousness, but contends that the course of interpretation must proceed in the contrary direction. Thus it will fit the facts with materialism rejected as supernatural and thereby attain an explanation which is ultimately tenable instead of one which is ultimately absurd. It is an explanation the possibility of which no evidence in favor materialism can possibly affect.


Schiller argued that brain injuries are better understood as preventing the manifestation of consciousness than as extinguishing it. He suggested that, with regard to memory, it is forgetfulness and not memory that needs to be explained by neuroscience. For example, he noted the remarkable clarity of total recall that many people have under hypnosis or experience in near-death scenarios.

Read the rest at Mind Matters News, published by Discovery Institute’s Bradley Center for Natural and Artificial Intelligence.