COVER STORY THE CONSCIOUSNESS WAGER In 1998, two top thinkers made a bet about whether the hardest problem in neuroscience would be cracked by 2023. With five years to go,Per Snaprud tracks down the pair to find out how close we’ve got WENTY years ago this week, two young progress has been made, but how close are we search for the “neural correlates of men sat in a smoky bar in Bremen, to solving the mystery? To find out, I decided consciousness”. Tnorthern Germany. Neuroscientist to ask Chalmers and Koch how their bet was This approach, which allows incremental Christof Koch and philosopher David going. But there was a problem – they had progress and appeals to researchers no matter Chalmers had spent the day lecturing at a mislaid the terms of the wager. Luckily, I too what their philosophical stance, has been conference about consciousness, and they still was in Bremen 20 years ago and was able to central to the study of consciousness ever had more to say. After a few drinks, Koch come to their rescue. since. Indeed, neural correlates of suggested a wager. He bet a case of fine wine The consciousness bet has its roots in Koch’s consciousness – the subject of Koch's wager – that within the next 25 years someone would research. In the mid-1980s, as a young was the topic under discussion at the Bremen discover a specific signature of consciousness scientist, he began collaborating with Francis conference. There, Koch argued that gamma in the brain. Chalmers said it wouldn’t happen, Crick who had co-discovered the double helix waves might be involved, based on research and bet against. structure of DNA. Both men were frustrated linking awareness to this kind of brain activity, It was a bit of fun, but also an audacious that science had so little to say about where neurons fire at frequencies around gamble. Consciousness is truly mysterious. consciousness. Indeed, the International 40 hertz. Conference delegates also heard that It is the essence of you – the redness of red, the Dictionary of Psychology described it thus: pyramidal cells in the brain’s outer layer or feeling of being in love, the sensation of pain “a fascinating but elusive phenomenon; it is cortex might play a key role (see “Where’s and all the rest of your subjective experiences, impossible to specify what it is, what it does, or consciousness?”, overleaf). conjured up somehow by your brain. Back why it evolved. Nothing worth reading has There was no shortage of ideas. However, then, its illusive nature meant that many been written about it.” The pair believed this the early ones all proved too simplistic. Take believed it wasn’t even a valid subject for was partly because researchers lacked a the notion, which Koch and Crick favoured for scientific investigation. practical approach to the problem. In his work a while, that a sheet-like structure beneath the Today, consciousness is a hot research area, on DNA, Crick had reduced the mystery of cortex called the claustrum is crucial for and Koch and Chalmers are two of its most biological heritability to a few intrinsic consciousness. There was reason to be influential figures. Koch is head of the Allen properties of a small set of molecules. He and optimistic: a case study in 2014 showed that Institute for Brain Science in Seattle. Chalmers Koch thought consciousness might be electrically stimulating this structure in a is a professor at New York University and explained using a similar approach. Leaving woman’s brain caused her to stare blankly famous for coining the phrase the “hard aside the tricky issue of what causes ahead, seemingly unconscious, until the problem” to distinguish the difficulty of consciousness, they wanted to find a minimal stimulation stopped. But another study understanding consciousness from that of physical signature in the brain sufficient for a described someone who remained fully grasping other mental phenomena. Much specific subjective experience. Thus began the conscious after his claustrum was destroyed > PICTURE CREDIT 26 | NewScientist | 23 June 2018 23 June 2018 | NewScientist | 27 by encephalitis, undermining that idea. “We had a good time. It got light very early and attention in the cortex and a structure in hot-zone in the posterior cortex but, rather Undeterred, those searching for the neural we walked back around 6 o’clock.” Even though the centre of the brain called the thalamus. surprisingly and contrary to Global Workspace correlates of consciousness have come up with he still hasn’t slept, his voice is remarkably If the signal it generates outcompetes other Theories, not in the front of the cortex.” more sophisticated ideas. But are we really any alert. Distant memories re-emerge. We are information, it is broadcast across the brain. He attached two papers he had recently co- closer to cracking the problem? Last year, I had in an outdoor restaurant under a hazy sky. Only then do you consciously register it. A authored to support this last point. They link the perfect opportunity to find out when I met Chalmers wears a black leather jacket and has popular version of this theory is that special the front of the cortex with monitoring and up with Chalmers at a consciousness shoulder-length hair. “workspace neurons” in the cortex, primarily reporting, but not subjective experience. He conference in Budapest, Hungary. Fast-forwarding through the tape I find in the front of the brain, broadcast information also pointed out that the back of the cortex has I asked him how his bet with Koch was what I’m looking for. Towards the end, through their long-range connections. much higher phi than the front, due to the shaping up. Looking a bit dejected, he told me Chalmers mentions the bet and specifies what connectivity of its neurons, and is therefore that they had met three months earlier in New kind of signature of consciousness it refers to: more closely coupled to consciousness York, and the subject of the wager came up. “a small set of neurons characterised by a Measuring experience according to IIT. “The intrinsic properties that “Sadly, neither of us could remember the small list of intrinsic properties. I think we Other network-based ideas suggest that we spoke about in Bremen would be the exact terms,” he said. It was then that I realised said less than 10.” Intrinsic properties could consciousness is the result of information intrinsic connectivity of neurons in [the] I might be able to help. Although I wasn’t with be, say, a neuron’s pattern of electrical firing, being combined so that it is more than the posterior cortex,” he wrote. So, the posterior them at the bar when it all happened, the or genes regulating the production of various sum of its parts. One that has grabbed much hot zone is Koch’s horse in the race. following day I had interviewed Chalmers, neurotransmitters. “And it will be clear in attention is integrated information theory Chalmers replied a few hours later, who mentioned the bet he had made just 25 years,” he says. Bingo! I emailed a clip from (IIT). It is the brainchild of neuroscientist highlighting the details of the bet. It is about hours earlier. the recording to Chalmers. He immediately Giulio Tononi at the University of Wisconsin, finding a link between a subjective experience INC/ALAMY COLLECTION EVERETT Back home, I started looking for notes from replied: “Thanks – this is great!” and forwarded who believes that the amount of and a small number of nerve cells with a our long-ago meeting. Eventually, I found a the message to Koch. consciousness in any system – which he calls handful of intrinsic properties. Chalmers cassette stowed away in a box on top of a shelf These days, the prevailing ideas of phi – can be measured. Very approximately, didn’t think that something associated with looks somewhat unlikely,” he says. “Well, that In the TV show Humans, in my study. The faded label read: “David consciousness have more to do with the phi will be high in a system of specialised phi should count as intrinsic: “I’m thinking we simply don’t know, Dave. This is what our finding the consciousness Chalmers interview”. After more searching, properties of networks of neurons than those modules that can interact rapidly and that phi is a network property of a group of institute does, and we just got $120 million to switch is easy – it’s under I found a tape recorder and pressed play. of specific cells. One proposal that has been effectively. This is true for large parts of the neurons, so not an intrinsic property of do more of it,” says Koch, referring to the Allen the chin Chalmers is describing how he left the particularly influential is called global brain’s cortex. In contrast, phi is low in the specific neurons,” he wrote. Another question Institute’s efforts to map and characterise conference banquet after midnight and workspace theory. It suggests that information cerebellum, which contains 69 billion of the was whether Koch’s hot zone constituted a different cell types in the brain. “OK,” says continued to a bar with Koch and a few others. coming from the outside world competes for 86 billion nerve cells that make up the human small group of neurons. “Overall, I agree that Chalmers. “But ‘we don’t know’ isn’t good “No!” he answers. Chalmers is more brain, but is composed of modules that work IIT is cool and shares something of the bold enough for you.