How do our brains work?

There are a lot of reasons I am interested in this question:

1. It’s probably the most complex machine nature has evolved. Yet it runs on the power of a 20watt lightbulb when an equivalent computer would require 24 million watts of power!

2. My dad has dementia. There is a whole lot of research going on into what causes this and what we might be able to do to prevent or even help with it in the future. Too late for him but hopefully in time for my children.

3. We are fast developing various forms of Artificial Intelligence and understanding the way our brains work will form the basis for some of the modelling of how “computer brains” may work.

This WaitButWhy post by TimUrban I am linking to is a monster: it’s very long and addresses several big topics. But as usual for Tim it sets things out in a sensible understandable way. It’s overall focus is on what Elon Musk’s Neuralink enterprise is hoping to achieve with Brain/Machine interfaces. But different components of the piece are in themselves so interesting that I feel like I should really just share pieces of it, each of which can pretty much be read as stand alone treatise.

So the first bit I am going to recommend is actually the second and third part of this treatise, which is the piece on how our brain works. Tim manages to pull together and summarise in quite a simple way, our current understanding of the brain, and I found it quite fascinating.

Here is the link Part 2: The Brain. Read part 2 and also part 3 which starts to talk about the challenges of creating Brain, Machine interfaces.

Some of the fascinating pieces that amazed me:

The three main components of the brain: reptilian (the part that keeps our bodies functioning, eg. Hearts and lungs pumping), the limbic system (the Paleo-mamillian system), our primitive survival system of instincts where we get our emotions along with a whole lot of other functionality and some memory functions, and the neo-mamillian outer cortex where we do all of our rational thought, processing and emotional control functions. Things like Daniel Kannehman’s Thinking Fast, Thinking Slow is all about the interaction between these second and third parts of the brain.

The structure and nature of neurons, the basic building blocks of our brains and how they connect and trigger each other is also explained. Did you know that they basically function a lot like a binary computer either sending a signal or not sending a signal? Their activation functions and connections are non linear but their firing is either on or off. I expected something much more analogue!

There are around 100 billion neurons in our brains. (Around about the same number of stars as there are in our galaxy to an order of magnitude – a number that always blows my mind. Think about that for a moment vs the 7bn people we have on earth. And that’s just our galaxy, one of an estimated 100 billion galaxies in the universe. Anyway back to earth and your brain…) Your thinking cortex is about 15 to 20% of that total number of neurons and is present only in the outer two milimeters of your brain! (The bulk of the brain below that is taken up with the connections between the axon of each neuron and the others). Each neuron can have synaptic connections (connections that can carry its signal) to between 1000 and 10,000 other neurons! And it’s the restructuring of these connections that gives us our ability to learn. Now that makes a seriously complex machine! Tim does a wonderful illustration scaling up the brain to the size of a few city blocks to try to describe its complexity in a way we can comprehend.

If you have the stamina then read the whole thing, you will need to go back to Part 1, which will be the topic of my next post. If not I am sure to pick up on many of the topics in future posts!