What is the purpose of the cerebral cortex?

The main part of the human brain is the cerebrum, the big piece of folded, wrinkly meat that covers the older, more primitive “snake brain” or limbic system and brainstem. Different areas of the cerebrum support different cognitive and bodily functions. In nearly all mammals, the brain has an extremely thin (no more than two-tenths of an inch thick) wrapper around it made up of neurons, and that is the cerebral cortex (“cortex” comes from the Latin for “cap.”). The cortex, thin though it is, actually is made of even thinner layers of cells, up to six distinct layers of so-called gray matter. While there are connections in and out of the cortex to the cerebrum underneath, more than 99% of cortical activity takes place strictly within the cortex alone.

Most animals do not have a cerebral cortex. Only mammals do, and among mammals, the human version is the largest and most complex. If billions of animals get along just fine without a cerebral cortex, it raises the question, what is it for? That is a mystery.

We know that sensory signals coming from the receptors eventually end up in the cortex. Visual data, for example, ends up at the back of the head in the so-called visual cortex. What it does there, we do not know. And we know that parts of the cortex send signals out to the muscles, presumably as part of coordinated actions. But what about the 99% of a cortex’s activity that goes on within the cortex itself? What is that about?

We don’t know what the function of the cortex is, but scientists believe, based on observations of people with brain damage, and on animal studies, that somehow, activity in the cerebral cortex produces meaningful experience of the world, and also, somehow, abstract thinking, planning and language. How that could be possible is a mystery, but that seems to be what is going on.

What’s the great mystery? The mystery is that we don’t know how a physical organ like the cortex could produce mental functions like thinking, planning, and language understanding. According to the principles of science, it is not actually possible. No physical activity can produce any nonphysical effect (energy is “physical”) like a thought. Why not? Because if it did, that would violate the law of conservation of matter and energy (and many other laws of nature besides), and if that can happen, well, then we don’t know anything about anything.

E=MC2 is only true because of the law of conservation of matter and energy, for example. Violate that law and you have nothing.

And it’s not just a matter of preserving the integrity of science’s precious little formulas. We can’t even conceive of how a physical thing like a group of neuron, which are just protein, fat, and a few chemicals, could cause or create something as intangible as an abstract thought or even the experience of color. How would that work ? It would have to be magic. We can’t think of any example of any machine, no matter how complex or fantastic, that could do such a thing.

Some scientists have become so frustrated with this problem that they have just declared that thoughts, experiences, and other intangible mental phenomena do not exist, except as illusions. But that is just crazy talk. Even an “illusion” is a mental phenomenon.

Despite this impenetrable mystery, we still want to ask, what is the cortex for and why do we have one, because its occurrence is quite rare in evolution.

1. Does the cortex produce or create the conscious mind in some way? That is scientifically impossible and even unintelligible, for reasons just described. Parts of the cortex are proven to be correlated with aspects of the conscious mind, but we cannot explain that correlation.

2. Does the cortex create and store a map of the whole body, including its history and modifications? Some scientists think so (e.g., Antonio Damasio). That would require an awful lot of capacity, since the body has a lot of parts and a very long history. Still, it might be possible. But what good would it do to have such a map? Who would look at it? There is no little man in the head.

3. Could the cortex have/be historical record of bodily connections as suggested above, not used as a map, but rather, as some kind of a switchboard, so that signals incoming to the brain get routed to the correct output action signals? That seems highly implausible to me, since there are an infinite number of possible combinations and sequences of sensory information that one encounters every day and just as large a number of movements that could be made in response. The brain is very large and complex, but it is not infinite in capacity, and the cortex is, after all, only 4 millimeters thick. Also, such a “switchboard” or “blackboard” hypothesis does not allow any scope for creative action, if every input is wired to an output or even to a selection of outputs. Some scientists deny that there is any such thing as creativity, but I am quite sure they are wrong.

4. Here is my hypothesis about what the cortex is for. I think it supports intersubjective social life. Intersubjectivity is a kind of empathy that allows humans to understand each other, and that’s what is necessary to have complex civilization like ours. Without empathy, there could be no poetry, no arts of any kind, no jurisprudence, no government, no sports, no teaching and learning, not even symbolic language.

Since we are the only species that indulges such things with such intensity, it makes sense that we have the most developed cerebral cortex. Chimps have societies and maybe elephants grieve over their dead. Most mammals have a cerebral cortex and so most are intersubjective to some degree. But no other mammals use symbolic language or have courts of law or try to entertain each other. We are the only ones with a hyper-developed cortex.

How would it work? It has been proven that the brain does physically change in response to learning and adaptation. So it is plausible to imagine that the cortex is a matrix for social learning. It stores all the intermediate states on the long social journey each one of us takes from infancy to adulthood and on to the grave.

The cortex does not store individual experiences as you would store marbles in a bag, but it would store developing subsystems. You need some kind of storage to accumulate and integrate experience over time, experience like complex social understanding; like intersubjective social learning. It is the skills of social mind-reading that are accumulated and integrated and refined in the cerebral cortex.

Those cortical representations of complex social understandings are not retrieved, as from a file (because there is nobody to read such a file anyway). Rather the representations are the basis for creatively responding to new social situations. They form the basis for creative projection beyond what is known, to what might be, and at the same time, they constrain creativity to what is feasible and acceptable within the social community. So each time a new situation comes up (and every situation is new in some way), you do not need to start from square one. You start your response from what you already have in the vast network of your cerebral cortex and creatively project something from that.

Where does that creative urge or impetus come from? I don’t know. That’s the magic part.