Rachel Neumeier

Fantasy and Young Adult Fantasy Author


Brain architecture is weird

So, did you know this?

[Birds] also have very different brains than mammals: while mammals have a neocortex arranged in a characteristic pattern of layers, birds have a different unlayered structure called the pallium with neurons “organized into nuclei”.

Here’s what that actually looks like:

The green part is considered to be used primarily for higher cognitive functions, incidentally.

Isn’t that remarkable? I took a class in comparative animal physiology, but I don’t remember ever hearing anything about the striking differences in brain architecture between birds and mammals before. Maybe that was included, but it seems like the kind of thing I would have remembered, so I don’t think it was.

Here is a post about the architecture and function of parts of the avian brain.

Here is another post about avian brains and intelligence.

Birds have another exceptional capacity that helps them to have small but intelligent brains. They can generate new neurons when they need them and shed them when they are no longer necessary. … For example, in those parts of the world where breeding is governed by the seasons, song birds sing only during the breeding season, and they do so using parts of the brain (nuclei) that have grown larger by recruiting new neurons that have recently been generated in other parts of the brain. Once the breeding season is over, the number of cells in these song nuclei declines because some of the cells die when not needed. 

That’s pretty neat.

And of course the octopus brain is very different from both:

Here’s a post about the octopus brain.

This is so freaky:

The octopus brain is split into two halves and then into many lobes with particular functions. These lobes are folded, which increases the surface areas and connections. Some regions have very small neurons where large numbers can be packed into a small compartment. Also, the distance between them is very short, which increases processing speeds.

The Vertical Lobe (VL) is the seat of learning and memory and is organized like the human hippocampus with many sensory inputs at right angles to the small neurons that process the information. …

The brain is divided into three parts, each with a hierarchy. The central brain, surrounded by cartilage, has 50 million neurons and surrounds the gut. The vision brain (with 150 million neurons) and the eight arm brains (with a total of 300 million distributed neurons) are outside of the central nervous system.

Aliens among us!

I was thinking about this because of Scott Alexander’s recent posts about brains and complex thought and human perception of the moral worth of various animals. This series of posts begins here:


Driven by the need to stay light enough to fly, birds have scaled down their neurons to a level unmatched by any other group. Elephants have about 7,000 neurons per mg of brain tissue. Humans have about 25,000. Birds have up to 200,000. That means a small crow can have the same number of neurons as a pretty big monkey.

Does this mean they are equally smart? There is no generalized animal IQ test, so nobody knows for sure. …

So does that mean that intelligence is just a function of neuron quantity? That the number of neurons in your brain, plugged into some function, can spit out your IQ?

It…comes pretty surprisingly close to meaning that. [Ellipse in the original.]

That is interesting, even though imo, AI people are not remotely near building anything that is at all intelligent, which is what the research Scott references is actually about. Stuff that fakes being intelligent, yes. Computers that are actually intelligent, no.

No, the reason it interests me is that it opens up so many different architectures by which we can get intelligence, and that is just fascinating.

If you would like to design an alien species that is small, but much more intelligent than seems reasonable for its size, no problem! If you care to do so, you can absolutely have a character comment about the very peculiar brain structures your alien species possesses. At the very least, if challenged by a reader, you can whip out your handy understanding of avian and octopus brain architecture.

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3 Comments Brain architecture is weird

  1. Elaine T

    (vaguely on topic) I saw an article that included the phrase “the neurobiology of storytelling”, or how our brains react to it.

    Guess what makes people react well, brain chemistry-wise? all the elements that make a good story. (duh) If I can find an online copy I’ll post a link

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