Brain’s Functional Geometry Encodes Dimensions of Consciousness, Neuroscientists Say

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Consciousness is a multidimensional phenomenon, but key dimensions such as awareness and wakefulness have been described conceptually rather than neurobiologically. Scientists at the University of Michigan Medical School hypothesized that dimensions of consciousness are encoded in multiple neurofunctional dimensions of the brain.

Huang et al. showed that the brain’s functional geometry (e.g., network distance in the gradient space) and temporal dynamics (e.g., occurrence rates of co-activation patterns) covary with the state of consciousness. Image credit: Gerd Altmann.

Huang et al. showed that the brain’s functional geometry (e.g., network distance in the gradient space) and temporal dynamics (e.g., occurrence rates of co-activation patterns) covary with the state of consciousness. Image credit: Gerd Altmann.

“Consciousness is complex and studying it is like solving a scrambled Rubik’s cube,” said Dr. Zirui Huang, a researcher with the Department of Anesthesiology at the University of Michigan Medical School.

“If you look at just a single surface, you may be confused by the way it is organized. You need to work on the puzzle looking at all dimensions.”

When it comes to consciousness, these dimensions can include:

(i) arousability, that is, the ability of the brain to be awake;

(ii) awareness, or what we actually experience, like the redness of a rose;

(iii) sensory organization, or how sights and sounds and feelings become woven together to create our seamless conscious experience.

For decades, though, these dimensions were just considered conceptually, without any mapping to brain activity itself.

In the new study, Dr. Huang and colleagues sought to find those dimensions of the mind in the geometry of the brain.

“Typically, brain imaging studies assess discrete, well-defined brain areas. To understand this, consider the state of Colorado on a map of the United States. It has very clear boundaries in an almost rectangular shape,” they said.

“However, the borders separating, for example, Colorado and Wyoming, are arbitrary.”

“By contrast, looking at the topology of the mountains across Colorado and Wyoming give you a more informative, natural view of the region.”

“We did something very similar in this neuroimaging study: instead of looking at clearly defined brain regions, we investigated the topology or gradients across brain regions.”

To develop a map of these so-called cortical gradients of consciousness, the researchers used fMRI data from study participants who were awake, anesthetized, in a form of coma, or who had psychiatric diagnoses such as schizophrenia.

They were then able to arrange recordings from 400 different brain regions into gradients and compare how they change in relation to these states or diagnoses.

They found three cortical gradients that seemed to align with the dimensions of consciousness, including arousability, awareness, and sensory organization.

“What used to be mapped only as a helpful diagram of conscious states might now be mapped in the brain itself,” said Dr. Anthony Hudetz, director of the Center for Consciousness Science at the University of Michigan Medical School.

“Our study opens a new view of the link between consciousness and the brain,” Dr. Huang said.

“Furthermore, the results have the potential for developing brain-based diagnoses or assessment for neurologic patients.”

“This article represents an important contribution to the science of consciousness and aligns with our mission of achieving deeper understanding while advancing clinical care,” said University of Michigan Medical School’s Professor George Mashour.

The team’s paper was published in the journal Nature Communications.

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Z. Huang et al. 2023. Functional geometry of the cortex encodes dimensions of consciousness. Nat Commun 14, 72; doi: 10.1038/s41467-022-35764-7

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