[Old notes.] I’m reading Stanislas Dehaene’s Consciousness and the Brain: Deciphering How the Brain Codes Our Thoughts (2014). Good book, sophisticated but readable. Explores what an unbelievable amount of the brain’s activity is unconscious. For instance, after reviewing a bunch of experiments, Dehaene states what should have been obvious all along (although of course it did need to be experimentally confirmed): “in some respects, consciousness is irrelevant to semantics—our brain sometimes performs the same exact operations, all the way up to the meaning level, whether or not we are aware of [the words we have been exposed to, e.g. because they were flashed on a computer screen too briefly for us to consciously notice them].” The brain can unconsciously process word meanings, just as it can unconsciously process the emotional valences of images, etc.
Dehaene also summarizes experiments that show that consciousness definitely isn’t epiphenomenal. Which is to say, there are a hell of a lot of things we couldn’t do if we weren’t conscious. Duh. One of consciousness’s evolutionary roles, for instance, is “learning over time, rather than simply living in the instant.” Subliminal (unconscious) perceptions and thoughts can’t be retained for longer than a second or so, whereas conscious ones can be retained for much longer. Another function may be to simplify and focus perception (since our brain is constantly receiving an enormous amount of sensory information). Also, we need consciousness in order to rationally think through a problem. The unconscious mind doesn’t seem able, by itself, to carry out steps of reasoning; it can carry out single operations but not a cumulative series of them. And of course social information sharing is likely another essential function of consciousness.
Interesting discussion of “the signatures of a conscious thought.” I’ll just quote a particularly easy-to-read thing that I find pretty incredible, and also eery: “With intracranial electrodes, the effects of stimulation can be very specific. Sparking off an electrode atop the face region of the ventral visual cortex can immediately induce the subjective perception of a face. Moving the stimulation forward into the anterior temporal lobe can awaken complex memories drawn from the patient’s past experience. One patient smelled burnt toast. Another saw and heard a full orchestra playing, with all its instruments. [!] Others experienced even more complex and dramatically vivid dreamlike states: they saw themselves giving birth, lived through a horror movie, or were projected back into a Proustian episode of their childhood. [Apparently] our cortical microcircuits contain a dormant record of the major and minor events of our lives, ready to be awakened by brain stimulation.” If you stimulate the subthalamic nucleus, the result is a state of depression, “complete with crying and sobbing, monotone voice, miserable body posture, and glum thoughts.”
Astounding. Not surprising, but astounding nonetheless. It’s obvious but incredible anyway that Beethoven’s Ninth Symphony is in my head, encoded in neural pathways, and theoretically can be elicited by the right stimulation.
In any case, “putting together all the evidence inescapably leads us to a reductionist conclusion. All our conscious experiences…result from a similar source: the activity of massive cerebral circuits that have reproducible neuronal signatures. During conscious perception, groups of neurons begin to fire in a coordinated manner, first in local specialized regions, then in the vast expanses of our cortex. Ultimately, they invade much of the prefrontal and parietal lobes, while remaining tightly synchronized with earlier sensory regions. It is at this point, where a coherent brain web suddenly ignites, that conscious awareness seems to be established.”
But what is consciousness? Here’s Dehaene’s answer:
When we say that we are aware of a certain piece of information, what we mean is just this: the information has entered into a specific storage area that makes it available to the rest of the brain. Among the millions of mental representations that constantly crisscross our brains in an unconscious manner, one is selected because of its relevance to our present goals. Consciousness makes it globally available to all our high-level decision systems. We possess a mental router, an evolved architecture for extracting relevant information and dispatching it. The psychologist Bernard Baars calls it a “global workspace”: an internal system, detached from the outside world, that allows us to freely entertain our private mental images and to spread them across the mind’s vast array of specialized processors [e.g., language, memory, the motor system, etc.].
So according to this theory, consciousness is just “brain-wide information sharing.” He goes on to suggest that this was likely an evolutionary adaptation: in the harsh natural environment, it was necessary to have a mental map of space, a visual recognition of landmarks, a recall of past successes or failures at finding water or food, and so on. “Long-term decisions of such a vital nature, leading the animal through an exhausting journey under the African sun [for example], must make use of all existing sources of data. Consciousness may have evolved, eons ago, in order to flexibly tap into all the sources of knowledge that might be relevant to our current needs.”
In truth, we should all just be constantly gaping at each other and ourselves, gasping at the miraculousness of everything. Trillions of neural impulses and unconscious computations going on at every moment of our life. All a result of...billions of years of blind evolution, matter coming together in ever-more-complex clumps to replicate itself in a harsh and unforgiving natural environment. To take a mundane example from The Brain: The Story of You:
Imagine we’re sitting together in a coffee shop. As we’re chatting, you notice me lift my cup of coffee to take a sip... The field of robotics still struggles to make this sort of task run without a hitch. Why? Because this simple act is underpinned by trillions of electrical impulses meticulously coordinated by my brain.
My visual system first scans the scene to pinpoint the cup in front of me, and my years of experience trigger memories of coffee in other situations. My frontal cortex deploys signals on a journey to my motor cortex, which precisely coordinates muscle contractions – throughout my torso, arm, forearm, and hand – so I can grasp the cup. As I touch the cup, my nerves carry back reams of information about the cup’s weight, its position in space, its temperature, the slipperiness of the handle, and so on. As that information streams up the spinal cord and into the brain, compensating information streams back down, passing like fast-flowing traffic on a two-way road. This information emerges from a complex choreography between parts of my brain with names like basal ganglia, cerebellum, somatosensory cortex, and many more. In fractions of a second, adjustments are made to the force with which I’m lifting and the strength of my grip. Through intensive calculations and feedback, I adjust my muscles to keep the cup level as I smoothly move it on its long arc upward. I make micro-adjustments all along the way, and as it approaches my lips I tilt the cup just enough to extract some liquid without scalding myself.
It would take dozens of the world’s fastest supercomputers to match the computational power required to pull off this feat. Yet I have no perception of this lightning storm in my brain. Although my neural networks are screaming with activity, my conscious awareness experiences something quite different. Something more like total obliviousness. The conscious me is engrossed in our conversation...
And it's all automatic, the automatic result of billions of cells interacting according to the laws of nature! (Scientists have no idea, and probably never will, how a person makes a decision to do something, how decisions, even trivial ones, well up out of the continuous “lightning storm” of deterministic neural activity.) The universe itself is no more wonderful than our own brains, our own bodies, which are themselves a magnificent, completely unfathomable universe.
 To get a sense of how utterly in the dark we are about nearly everything pertaining to the brain, think of this: we still have no idea why it is that one person is talented at music, another at math, another at painting, etc. We don't know what it is about neurons that specializes some of them in speech, others in music, others in spatial reasoning, and so on. It's hard even to imagine what it could be that allots 'specialties' to particular groups of neurons. Nor is it clear how we'd go about discovering what these mysterious mechanisms are. The extent of our knowledge is that when you do a certain activity, some region of the brain lights up, and with another activity a different region lights up. That's it! The primitiveness of this kind of knowledge is embarrassing.