To say what consciousness is, science explores where it isn’t


EXCERPTS (Joel Frohlich): In 2014, a month-long bout of dizziness and vomiting brought a 24-year-old woman in China to the hospital [...] These were serious, debilitating symptoms. And yet, they might have seemed almost mild once CT and MRI scans presented a diagnosis: the woman was missing the majority of her brain – in a manner of speaking.

Yes, most of the players on the brain’s ‘stage’ were present [...] But none of these arenas hold the majority of the brain’s currency ... This distinction goes to the cerebellum, a structure situated behind the brainstem and below the cerebral cortex. Latin for ‘little brain’, the highly compact cerebellum occupies only 10 per cent of the brain’s volume, yet contains somewhere between 50 and 80 per cent of the brain’s neurons. And indeed, it was in this sense that the hospitalised Chinese woman was missing the majority of her brain. Incredibly, she had been born without a cerebellum, yet had made it through nearly two and a half decades of life without knowing it was missing.

[...] Understanding consciousness might be the greatest scientific challenge of our time. How can physical stuff, eg electrical impulses, explain mental stuff, eg dreams or the sense of self? Why does a network of neurons in our brain feel like an experience, when a network of computers or a network of people doesn’t feel like anything, as far as we know? Alas, this problem feels impossible. And yet, an unmet need for progress in disorders of consciousness, in which the misdiagnosis rate is between 9 and 40 per cent, demands that we try harder. Without trying harder, we’ll never know if injured patients are truly unconscious – or unresponsive but covertly conscious with a true inner life. Without this knowledge, how can doctors know whether a patient is likely to recover or whether it’s ethical to withdraw care?

Many covertly conscious patients differ from those we know from popular culture [...] To detect covert consciousness in patients diagnosed with disorders of consciousness, an international team of researchers, including my current supervisor, Martin Monti, have used a clever task that exploits the mental imagery that some otherwise unresponsive patients can generate on command.

[...] The resulting study, eventually published in 2010, was simultaneously hopeful and sobering: five out of 54 patients placed in the scanner were able to generate mental imagery on demand, evidence of minds that could think, feel and understand, but not communicate. Or could they? What if patients could use the two tasks to respond to questions, answering ‘yes’ through internal imagery itself. In short, ‘yes’ could be communicated by imagining tennis and ‘no’ by imagining walking around their house. Once again, the team found success on their very first attempt...

Following in the footsteps of Monti and his colleagues, a study published in 2018 by a different group of researchers from the University of Michigan used a similar fMRI mental-imagery task to show covert consciousness where no one wants to find it: anaesthesia. Alarmingly, one out of the five healthy volunteers who had undergone general anaesthesia [...] was able to do what shouldn’t be possible: generate mental imagery upon request in the scanner. The implications are clear: we aren’t necessarily blissfully unconscious when the surgeon puts us under.

[...] Consciousness can also occur without language comprehension or hearing. In their absence, a patient might still experience pain, boredom or even silent dreams. [...] Consciousness is a mystery. A multitude of scientific theories attempt to explain why our brains experience the world, rather than simply receiving input and producing output without feeling.

Some of those theories are ‘out there’ – for instance, the framework developed by the British theoretical physicist Sir Rodger Penrose and the American anaesthesiologist Stuart Hameroff. Penrose and Hameroff link consciousness to microtubules [...] Consciousness enters the picture largely due to an interpretation of quantum physics ... This makes sense to Hameroff but not to me.

An approach that I find more promising comes from the neuroscientist Giulio Tononi at the University of Wisconsin. Rather than asking what brain processes or brain structures are involved in consciousness, Tononi approaches the question from the other direction, asking what essential features underly conscious experience itself.

[...] Just as life stumped biologists 100 years ago, consciousness stumps neuroscientists today. It’s far from obvious why some brain regions are essential for consciousness and others are not. So Tononi’s approach instead considers the essential features of a conscious experience. When we have an experience, what defines it? First, each conscious experience is specific. Your experience of the colour blue is what it is, in part, because blue is not yellow. If you had never seen any colour other than blue, you would most likely have no concept or experience of colour. Likewise, if all food tasted exactly the same, taste experiences would have no meaning, and vanish. This requirement that each conscious experience must be specific is known as differentiation.

But, at the same time, consciousness is integrated. This means that, although objects in consciousness have different qualities, we never experience each quality separately. When you see a basketball whiz towards you, its colour, shape and motion are bound together into a coherent whole. During a game, you’re never aware of the ball’s orange colour independently of its round shape or its fast motion. By the same token, you don’t have separate experiences of your right and your left visual fields – they are interdependent as a whole visual scene.

Tononi identified differentiation and integration as two essential features of consciousness. [...] Future engineers of consciousness-detectors, pay careful attention: these properties are exactly what such a fantastic machine should look for in the brains of unresponsive patients. Because consciousness is specific, a physical system such as the brain must select from a large repertoire of possible states to be conscious. ... Experiences are informative because they rule out other experiences ... we infer that, as one’s consciousness increases, so too does information in the brain. ... as does its capacity for highly differentiated conscious experiences. But at the same time, consciousness depends on integration: neurons must communicate and share information, otherwise the qualities contained in a conscious experience are no longer bound together.

This simultaneous requirement for both differentiation and integration might feel like a paradox. Here, a metaphor borrowed from Tononi offers clarity: the conscious brain is like a democratic society. Everyone is free to cast a different vote (differentiation) and talk to one another freely (integration). The unconscious brain, on the other hand, is more like a totalitarian society. Citizens might be forbidden to talk freely to one another (a lack of integration), or they might be forced to all vote the same way (a lack of differentiation).

Just as both differentiation and integration are necessary for democracy, they’re also necessary for consciousness. This is not merely an armchair musing: Tononi’s ideas are based on clinical observations. [...] Tononi’s theory that both differentiation and integration are required for consciousness is known as integrated information theory (IIT). Using IIT, one can systematically predict which brain regions are involved in consciousness (the cerebral cortex) and which are not (the cerebellum). In the clinic, ideas derived from IIT are already helping researchers infer which brain-injured patients are conscious and which are not.

[...] But more mysteries of consciousness remain. ... I’m currently investigating why children with a rare genetic disorder called Angelman syndrome display electrical brain activity that lacks differentiation even when the kids are awake and experiencing the world around them. There’s no question that these children are conscious, as one clearly sees from watching their rich spectrum of purposeful behaviour. And yet, placing an EEG cap on the head of a child with Angelman syndrome reveals Tononi’s metaphorical totalitarian society – neurons that appear to be locked into agreement. By showing us what types of brain activity are and aren’t essential for consciousness, patients with Angelman syndrome could offer insights into consciousness similar to those offered by patients lacking part or all of the cerebellum.

[...] Consciousness might be the last frontier of science. If IIT continues to guide us in the right direction, we’ll develop better methods of diagnosing disorders of consciousness. One day, we might even be able to turn to artificial intelligences – potential minds unlike our own – and assess whether or not they are conscious. This isn’t science fiction: many serious thinkers ... are deeply concerned about the existential risk that could be posed by human- or superhuman-level AI in the future. When is unplugging an AI ethical? Whoever pulls the plug on the super AI of coming decades will want to know... Understanding consciousness really matters – after all, the wellbeing of conscious minds depends on it... (MORE - details)

Possibly Related Threads…
Thread Author Replies Views Last Post
  Measuring consciousness in the lab + Science as a holistic detective agency C C 1 747 Jan 30, 2016 09:13 PM
Last Post: Magical Realist

Users browsing this thread: 1 Guest(s)