“Its key is to recognise that explaining why consciousness exists at all is not necessary in order to make progress in revealing its material basis – to start building explanatory bridges from the subjective and phenomenal to the objective and measurable.”
“But there is an alternative, which I like to call the real problem: how to account for the various properties of consciousness in terms of biological mechanisms; without pretending it doesn’t exist (easy problem) and without worrying too much about explaining its existence in the first place (hard problem).”
“A good starting point is to distinguish between conscious level, conscious content, and conscious self.”
“Conscious level has to do with being conscious at all – the difference between being in a dreamless sleep (or under general anaesthesia) and being vividly awake and aware.”
“Conscious contents are what populate your conscious experiences when you are conscious – the sights, sounds, smells, emotions, thoughts and beliefs that make up your inner universe.”
“And among these conscious contents is the specific experience of being you. This is conscious self, and is probably the aspect of consciousness that we cling to most tightly.”
“Gerald Edelman (my former mentor at the Neurosciences Institute in San Diego) and Giulio Tononi – now at the University of Wisconsin in Madison – argued that conscious experiences were unique in being simultaneously highly ‘informative’ and highly ‘integrated’.”
“Consciousness is informative in the sense that every experience is different from every other experience you have ever had, or ever could have.”
“Consciousness is integrated in the sense that every conscious experience appears as a unified scene.”
“It turns out that the maths that captures this co-existence of information and integration maps onto the emerging measures of brain complexity I described above. This is no accident – it is an application of the ‘real problem’ strategy.”
“Some researchers take these ideas much further, to grapple with the hard problem itself. Tononi, who pioneered this approach, argues that consciousness simply is integrated information. This is an intriguing and powerful proposal, but it comes at the cost of admitting that consciousness could be present everywhere and in everything, a philosophical view known as panpsychism.”
“When we are conscious, we are conscious of something. What in the brain determines the contents of consciousness? The standard approach to this question has been to look for so-called ‘neural correlates of consciousness’ (NCCs).”
“In the 19th century, the German polymath Hermann von Helmholtz proposed that the brain is a prediction machine, and that what we see, hear and feel are nothing more than the brain’s best guesses about the causes of its sensory inputs.”
“The classical view of perception is that the brain processes sensory information in a bottom-up or ‘outside-in’ direction: sensory signals enter through receptors (for example, the retina) and then progress deeper into the brain, with each stage recruiting increasingly sophisticated and abstract processing. In this view, the perceptual ‘heavy-lifting’ is done by these bottom-up connections. The Helmholtzian view inverts this framework, proposing that signals flowing into the brain from the outside world convey only prediction errors – the differences between what the brain expects and what it receives. Perceptual content is carried by perceptual predictions flowing in the opposite (top-down) direction, from deep inside the brain out towards the sensory surfaces. Perception involves the minimisation of prediction error simultaneously across many levels of processing within the brain’s sensory systems, by continuously updating the brain’s predictions.”
“In this view, which is often called ‘predictive coding’ or ‘predictive processing’, perception is a controlled hallucination, in which the brain’s hypotheses are continually reined in by sensory signals arriving from the world and the body. ‘A fantasy that coincides with reality,’ as the psychologist Chris Frith eloquently put it in Making Up the Mind (2007).”
“Armed with this theory of perception, we can return to consciousness. Now, instead of asking which brain regions correlate with conscious (versus unconscious) perception, we can ask: which aspects of predictive perception go along with consciousness? A number of experiments are now indicating that consciousness depends more on perceptual predictions, than on prediction errors.”
“Of the many distinctive experiences within our inner universes, one is very special. This is the experience of being you. It’s tempting to take experiences of selfhood for granted, since they always seem to be present, and we usually feel a sense of continuity in our subjective existence (except, of course, when emerging from general anaesthesia). But just as consciousness is not just one thing, conscious selfhood is also best understood as a complex construction generated by the brain.”
“There is the bodily self, which is the experience of being a body and of having a particular body.”
“There is the perspectival self, which is the experience of perceiving the world from a particular first-person point of view.”
“The volitional self involves experiences of intention and of agency – of urges to do this or that, and of being the causes of things that happen.”
“At higher levels, we encounter narrative and social selves.”
“The narrative self is where the ‘I’ comes in, as the experience of being a continuous and distinctive person over time, built from a rich set of autobiographical memories.”
“And the social self is that aspect of self-experience that is refracted through the perceived minds of others, shaped by our unique social milieu.”