https://www.nature.com/articles/d41586-023-02120-8
Christof Koch wagered David Chalmers 25 years ago that researchers would learn how the brain achieves consciousness by now. But the quest continues.
A 25-year science wager has come to an end. In 1998, neuroscientist Christof Koch bet philosopher David Chalmers that the mechanism by which the brain’s neurons produce consciousness would be discovered by 2023. Both scientists agreed publicly on 23 June, at the annual meeting of the Association for the Scientific Study of Consciousness (ASSC) in New York City, that it is an ongoing quest — and declared Chalmers the winner.
What ultimately helped to settle the bet was a study testing two leading hypotheses about the neural basis of consciousness, whose findings were unveiled at the conference.
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The findings from one of the experiments — which involved several researchers, including Koch and Chalmers — were revealed on Friday at the ASSC meeting. It tested two of the leading hypotheses: integrated information theory (IIT) and global network workspace theory (GNWT). IIT proposes that consciousness is a ‘structure’ in the brain formed by a specific type of neuronal connectivity that is active for as long as a certain experience, such as looking at an image, is occurring. This structure is thought to be found in the posterior cortex, at the back of the brain. GNWT, by contrast, suggests that consciousness arises when information is broadcast to areas of the brain through an interconnected network. The transmission, according to the theory, happens at the beginning and end of an experience and involves the prefrontal cortex, at the front of the brain.
Six independent laboratories conducted the adversarial experiment, following a preregistered protocol and using various complementary methods to measure brain activity. The results — which haven’t yet been peer reviewed — didn’t perfectly match either of the theories.
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“With respect to IIT, what we observed is that, indeed, areas in the posterior cortex do contain information in a sustained manner,” Melloni says, adding that the finding seems to suggest that the ‘structure’ postulated by the theory is being observed. But the researchers didn’t find evidence of sustained synchronization between areas of the brain, as had been predicted.
In terms of GNWT, the researchers found that some aspects of consciousness, but not all of them, could be identified in the prefrontal cortex. Furthermore, the experiments found evidence of the broadcasting postulated by advocates of the theory, but only at the beginning of an experience — not also at the end, as had been predicted.
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What it means is that proponents need to rethink the mechanisms they proposed in light of the new evidence.
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As for the bet, Koch was reluctant to admit defeat but, the day before the ASSC session, he bought a case of fine Portuguese wine to honour his commitment. Would he consider another wager? “I’d double down,” he says. “Twenty-five years from now is realistic, because the techniques are getting better and, you know, I can’t wait much longer than 25 years, given my age.”
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