The organ of intelligence

How the neocortex is organized to produce intelligence in humans

Author’s Note: I apologize for not hitting your inbox consistently over the last few weeks — there have been a lot of changes in my personal life that have kept me busy. Luckily, the dust has started to settle so you can continue to expect Synapse twice a month going forward!

One of my goals for Synapse going into 2021 was to write more about how the brain actually works. There are a mountain of facts about the brain that you can find in neuroscience textbooks. Over 100 years, hundreds of thousands of papers, and millions of hours of research have resulted in many detailed understandings of aspects of the complex organ between our ears, yet if you ask an expert in this field to explain—succinctly—how the brain creates intelligence, you aren’t going to get a satisfying answer.

In 1979, Francis Crick famously wrote:

“In Spite of the steady accumulation of detailed knowledge, how the brain works is still profoundly mysterious.”

Neuroscience is still looking for a theory of intelligence that will do for the field what Einstein’s theory of special relativity did for physics: provide a lens through which to interpret the collection of facts we have about how the brain works.

One scientist who is working to get us closer to that goal is Jeff Hawkins, computer pioneer, neuroscientist, and cofounder of the neuroscience company Numenta. He as written a book titled A Thousand Brains and I’m going to share with you a few key insights that have fascinated me from this book over the next few editions of the Synapse.

Living is a tall task for a brain

The first thing that Hawkins highlights in his book is the astonishingly complex task that just living everyday life presents for a brain. Over the course of our life, we have to learn what hundreds of thousands of objects look, sound, and feel like, hold tens of thousands of words in our vocabulary, and build relationships with a couple hundred people. We have a remember where everything important is in our environment, learn high level concepts such as “justice”, and keep track of our memories and plan for the future.

Oh, and do all of this while keeping track of our own bodies in time and space for every moment we are awake.

Living is a incredibly tall task for a brain and so a question naturally arises from this summation: how is it that our brains handle this task seemingly effortlessly?

The Neocortex: The Organ of Intelligence

Hawkins summarizes a few basic facts about the brain that will help us understand his theory of intelligence. First, we have observed that the human brain we see today is the result of compounding complexity over the history of evolution such that our “old brain” resides in the center—or core—of our brain and controls basic bodily functions such as sleeping, digestion, and breathing. Over evolutionary time, increasingly complex layers have evolved on top of the “old brain” to produce more intelligence life forms all of the way until the outermost layer—the folded, wrinkly part we all recognize in cartoons of the brain—the neocortex.

The neocortex represents 70% of the brain by volume. It is so large that it must be folded up to fit in our skull. According to Hawkins, if you were able to unfold the neocortex and stretch it out, it would be about the size of a large dinner napkin but about twice as thick. The neocortex is organized into layers first observed by Ramon y Cajal over 100 years ago:

Hawkins summarizes three critical observations about the neocortex that any correct theory of intelligence must account for:

1. The local circuits in the neocortex are complex

In just 2.5 cubic millimeters (approximately the size of a grain of rice) of the neocortex there are roughly 100,000 neurons, 500,000,000 synapses, and several hundred kilometers of axons and dendrites. Living may be a tall task for brains, but this kind of complexity must be one reason the brain can do it.

2. The neocortex looks similar everywhere

We now know that different parts of the neocortex perform different functions—visual, auditory, touch, etc… Yet the organization of the neocortex is remarkably similar across the entire organ. The part of the brain that is in charge of vision is organized in the same way as the part that processes language even though these are very different tasks.

3. Every part of the neocortex generates movement

Every part of the brain connects with a relevant part that controls your motor system. The auditory regions of the brain connect with the motor parts that move the head, etc… This makes sense considering that moving your head changes what you hear. Any correct theory of intelligence must be able to explain why intelligence must be so intimately related to the movement of our body.

Next Time: A Thousand Brains theory of intelligence

Overall, we learned about the astonishing task that our brain undertakes to understand our world and how an organ like the neocortex is organized the tackle this task. In the coming weeks, I’ll be writing about some of the key observations that Hawkins and others have made as to how the neocortex actually works given its amazing structure.

Until then, thanks for reading!

⚡️P.S. If you're new here and want to read more of the Synapse Newsletter every other Sunday, subscribe below!⚡️