What part of the brain gives rise to consciousness? Despite numerous theories, the neuroscience community has yet to converge on a definitive answer, chiefly due to the complexity of scientifically probing consciousness. It remains an elusive phenomenon that can’t be directly observed. “I can see how you act and can monitor your brain activity through methods like intracranial EEG, but I can never see your actual experience,” notes Robert Chis-Ciure, a postdoctoral researcher focused on consciousness at the University of Sussex in England.

Researchers primarily focus on two major theories to explain the emergence of consciousness: integrated information theory (IIT) and global neuronal workspace theory (GNWT). These theories are fundamentally different in their assumptions, scientific underpinnings, and perhaps even in their definitions of consciousness, according to Anil K. Seth, a consciousness researcher also at the University of Sussex.

In an effort to directly compare these theories, a collaboration involving 12 labs, known as the Cogitate Consortium, embarked on a large brain-imaging study. The results, fully published in Nature on a recent Wednesday, did not declare a clear winner and instead posed even more questions. Earlier in 2023, preliminary results were shared on the preprint server bioRxiv. Shortly thereafter, a group of academics labeled IIT as “pseudoscience” and sought to remove it from scientific discourse. As the debate continues, leading minds in the study of consciousness view the Cogitate findings as a step forward in understanding how consciousness develops, regardless of which theory may ultimately prevail.

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“We’re all adept at building ‘castles in the sky’ with abstract concepts,” observes Chis-Ciure, who did not participate in the recent study. “Data helps ground these ideas.”

Exploring the Two Major Theories of Consciousness

The two theories at odds in this debate are quite the opposites. “These theories are very different beasts,” states Christof Koch, a cognitive scientist at the Allen Institute in Seattle and co-author of the Cogitate findings. GNWT utilizes psychological insights to propose that consciousness functions like a stage where stimuli such as loud noises or vivid colors are spotlighted when they enter our awareness.

Conversely, IIT begins by abstractly defining consciousness and then conceptualizes the qualities a system needs to possess to experience consciousness. According to IIT, consciousness stems from information processing—the more information processed, the greater the level of consciousness, in simple terms.

Both theories offer testable hypotheses about brain activity during conscious perception. GNWT suggests that the frontal brain regions, like the prefrontal cortex, illuminate information during initial conscious awareness, a phenomenon known as ignition, which should be observable in imaging studies. IIT, however, posits that consciousness is more likely to manifest in the rear of the brain, where neural networks are denser, explains Koch.

Launched in 2018, the Cogitate Consortium aimed to test these theories in controlled environments across several labs. The study involved 256 participants who performed visual tasks while undergoing brain imaging, using three different techniques. This large-scale approach provided a robust data set for comparison.

The findings were challenging for both theories as neither fully aligned with the empirical data. For example, GNWT’s prediction about the detection of signals in the prefrontal cortex when a stimulus is removed was not observed.* “The absence of expected results poses a significant challenge,” comments Seth, who was not involved in the latest study. Similarly, the anticipated sustained neural synchrony in the back of the brain, as per IIT, was not detected.

The nuanced results were anticipated. “It was always understood that no single experiment would completely refute a theory,” Seth remarks. Science builds knowledge incrementally, and altering the consensus in a community often takes time.

Can Scientists Determine the Source of Consciousness?

The inconclusive results were first presented at a conference in June 2023. At this event, Koch and philosopher David Chalmers addressed a longstanding bet from 1998, where Koch wagered that the origins of consciousness would be determined within 25 years. Koch acknowledged his loss at the 2023 conference.

In September of the same year, an open letter challenging the scientific credibility of IIT circulated online, labeling it as “pseudoscience” due to its non-falsifiable core principles. This letter attracted over 100 signatures. Critics associate IIT with panpsychism, suggesting that if consciousness is a product of complex information processing, then potentially anything from a microchip to the universe could be conscious.

This attempt at “scientific excommunication,” as Seth phrases it, was debated extensively in Nature Neuroscience recently. IIT represents a daring approach to understanding consciousness, and “we must have the liberty to be wrong and the obligation to be daring,” Seth wrote in a journal commentary.

Seth believes that the results of the Cogitate study didn’t spur the open letter but rather reflect a field at a crossroads, needing more precise theories.

Looking Ahead

In a parallel to the famous 1919 solar eclipse that confirmed Einstein’s theory of relativity over Newton’s, Koch and his peers sought to similarly test competing theories of consciousness. This type of adversarial collaboration, where theorists test each other’s predictions under controlled, unbiased conditions, may pave the way for future research methodologies. Ongoing adversarial studies, including one where Seth serves on the steering committee, continue to explore these ideas.

This approach may foster a new way of conducting studies, focusing on designing experiments that best differentiate between competing theories rather than supporting or contradicting a single theory, according to Seth.

While the quest to explain consciousness is daunting, it’s crucial for practical applications such as understanding consciousness in brain-damaged or comatose patients, or during anesthesia. “The stakes of misunderstanding consciousness are too high, given its implications in life-support decisions,” Chis-Ciure points out.

*Editor’s Note (4/30/25): This sentence was edited after posting to correct the description of the GNWT prediction that was largely absent in the findings.