Deep thinking: where does your consciousness actually exist?

number3699
19 hours ago
6 min read

Most neuroscientists locate consciousness in our wrinkly cortexes, the outer layer of our brains where thought and sensation are supposed to live. But a growing band of rebels says the lights of experience may switch on far deeper, in the brain’s ancient core. And that cracks the door open to an even stranger idea. Could awareness be everywhere?

(First published on my Substack where you can get #NerdNews, marvellous maths and general geekery.)

("Where?": created by the author via imagen)

Not ‘What?’ but ‘Where?’

Any regular reader of NerdNews will know I love fathoming the almost-by-definition unfathomable question, "what is consciousness?". As I like to say, it's hard to think about how you think, using the very thing with which you think.

Last edition we met the neuros, computer scientists and philosophers asking serious questions about whether AI is developing consciousness. Let’sremind ourselves, we haven’t even sorted our noggins yet.

And as much as I’ve pondered what is it, I'd never really wondered where, in my brain, consciousness resides. Well a recent Scientific American article did exactly that, profiling the increasingly less radical position that it might bubble up from deep in our brains, in the region known as our subcortex.

Your double-decker brain.

Think of your brain as constructed in two broad storeys. The cortex is the outer sheet that handles language, abstract thought and self-reflection. The wrinkly feature in my NerdNews logo no less.

As you read this it comprises about 75 per cent of your brain mass. Beneath it sits the older subcortex, which manages arousal, emotion, body regulation and the relaying of sensory signals. The two are in constant conversation. Most sensory information passes up through subcortical relays to the cortex, which then fires feedback signals back down.

(A diagram of the brain I created via imagen. Reasonably accurate but don't use for surgery!)

Roll your way through these beautifully written paragraphs and that's your cortex at work, turning the squiggles into words and hoovering up the meaning. But the little flush of pleasure you feel when you think "wow, this Spence guy writes beautifully, if a touch self-absorbed", that warm glow is your subcortex kicking in. It does the feeling, not the thinking. Tell it I said hi.

For decades the default assumption has been corticocentric: that experience is manufactured upstairs. Subcorticalists such as neuropsychologist Mark Solms argue this is the consciousness equivalent of believing the Sun orbits the Earth. Almost everyone agrees that damaging certain brainstem structures makes "the lights go out", a clinical fact established for close to a century. The argument is over whether the subcortex is merely the power supply for the cortex's show, or can run a simple version of the show on its own.

The kids are not all zombies.

Research in this field regularly calls on the experience of people living with atypical brains.

Children born with hydranencephaly, for example, essentially have no cortex and are routinely classified as unconscious.

Cottier recounts that in October 2004 Swedish neuroscientist Bjorn Merker spent a week with five such families at Disney World, watching the children giggle, play and react to the world around them. He could not believe he was among "philosophical zombies", beings that behave normally but feel nothing inside. Mark Solms makes the same case: the proof they are not zombies is the same proof your dog isn't one. It's in their behaviour.

But here we bump up against the issue we met last NerdNews when trying to assess machine sentience. Appearing conscious and being conscious are not the same.

In the eerie phenomenon of blindsight, people with a damaged visual cortex respond to objects they insist they cannot see. So reactive behaviour can run with no inner feeling attached, which is precisely what a corticalist suspects is happening in these children.

"Even experiencing a dim light ... would require something like the cortex." — Professor Matthias Michel, MIT.

Feeling our way to consciousness.

Most consciousness research obsesses over vision, which, as blindsight shows, can clearly run unconsciously. Solms thinks that is the wrong place to start. He argues we should begin with feelings, which he takes to be conscious by their very nature. His argument is that once an organism juggles competing needs such as, eating, mating, fleeing a predator, it needs feelings to set the priorities.

"We feel so that we can transcend instinct." — Mark Solms, Professor of Neuropsychology, University of Cape Town.

If feeling really is that basic, the consciousness club gets a lot more crowded. The subcortical wiring credited with experience traces back to the Cambrian explosion more than 500 million years ago, far older than the mammalian cortex (which the Scientific American piece dates to roughly 300 million years ago).

In April 2024 the New York Declaration on Animal Consciousness, since signed by hundreds of researchers including Anil Seth, Christof Koch and David Chalmers, stated that the evidence points to a realistic possibility of conscious experience in all vertebrates and many invertebrates, octopuses and insects included.

"Consciousness is not... a cognitively sophisticated function but something far more elementary." — Bjorn Merker.

So how low can we go?

Why stop at the top floor of the duplex? Could consciousness come from outside the brain entirely? Cue a fascinating, perhaps bizarre, much older idea enjoying a serious revival.

Panpsychism holds that consciousness, or at least a primitive seed of it, is not a rare, ‘late to the party’ arrival in the universe, but a far more basic ingredient. Not something reliant on the incredibly complex arrangement of atoms that make up us, but something with roots far further down.

("All the way down": created via imagen)

Philosopher Philip Goff is one of its most prominent living champions.

Its scientific cousin is Integrated Information Theory, in which Giulio Tononi and Christof Koch argue that experience tracks “integrated information”. That it relates to the extent to which something is more than just the sum of its parts. In the formal IIT 4.0 paper, Larissa Albantakis and colleagues say the theory can be applied to any system of units to ask whether it is conscious, to what degree, and in what way.

“I argue that we live in a universe of space, time, mass, energy, and consciousness arising out of complex systems.” — Christof Koch, Wired Magazine 15 November 2013.

By this formulation, even a humble photodiode, which integrates a whisker of information – sure not a brain, but busier than a rock - may carry the faintest flicker of experience.

Unsurprisingly plenty of heavyweights push back hard. Physicist Sean Carroll argues that granting simpler collections of atoms a dash of mind sits uneasily with the known laws of physics. Philosopher John Searle scoffs at smearing consciousness "like jam" across the universe. Anil Seth calls it untestable, and therefore a scientific dead end.

Last edition it was the Pope vs Anthropic. Now, “do atoms have feelings?”.

I’m gonna need me some more popcorn!

Good vibrations.

So who is right?

TBH the evidence is not yet there to settle it.

The exciting twist is a tool called transcranial focused ultrasound, which can prod deep brain structures through an intact skull with millimetre precision. It is early days yet, but Matthias Michel holds if stimulating the subcortex restored the sensation of pain to someone whose cortex had lost it, he would be blown away.

Until that data lands, where consciousness actually lives remains wide open.

Well that’s ‘consciousness week’ done and dusted for NerdNews.

Until we next get down to thinking … about thinking … happy thoughts.