The Thousand Brains Theory - Reviewed

Live today (soon).

This is a review of A Framework for Intelligence and Cortical Function Based on Grid Cells in the Neocortex.


Paper that discusses the accumulation of features using evolution.
Some retained features are remnants of prior configurations of the genome.
In particular, see figure 2.

Resynthesizing behavior through phylogenetic refinement - Paul Cisek


That’s a really illuminating chart, but I’m wondering how do you distinguish retained features from the constituents/founding ones?

What exactly would you call a vestigial tail in humans?

For instance, the crossed visual paths, I think, can be considered a good example of such.

Good call!
If I understand the history of the eye (not an area I have studied much) the eye used to be part of the neural sheet we call the brain.

The mechanisms that form the structures of the brain are things like sheets forming new layers and splitting apart like pulling taffy. Connections can form between areas that used to be one - chemical signals guide the growing axons back to the scent of self across what is for a neuron- vast distance.

The chemical signal do a surprisingly good job of maintaining topology from map to map. Later in development there is a savage pruning process where neurons that are not connected correctly die. I surmise that if the neurons don’t get the correct chemical signal it works something like organ rejection in transplants.

A common theme is connection between pairs of very distant maps in different lobes.
For the eye - this is all the way from very far in the front to very far in the back. The left/right split in the eye and occipital lobe must have happened before the retina made it’s long journey ending in the eye structure, and before the eye underwent it’s specialized transformation into a visual sensor.

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I believed the proto eye (even before splitting to two eyes) evolved before the formation of the central neuron system. Perhaps it all could be considered as a distributed proto brain…

Anyhow, the intention of my question was to ask about any known or suggested the retained features which could be substructed from the current understanding of the brain, to get some simplification of it.

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I think the massive energy consumption of the neural hardware has driven aggressive elimination of useless features.

The functional power of the old brain has retained these functions as drivers of the cortex.

If you want to understand the functions of the brain you will have to leave the seductive regularity of the cortex and descend into the hardwired complexity of the lizard brain.

Evolution has had much longer to dial in the functions in the lizard brain and try (and adopt) weird experiments.

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I believe you are right about the role of the old brain, still, as for me, it’s the biggest retained structure we have (but not the functions of it).
Fortunately, its functions are not so complicated, if we don’t care about the reproduction of all weird stuff evolution has produced during millions of years of tinkering and adapting to the environment which is not actual anymore.
On the other hand, the general algo of the neocortex processing is were all good stuff is originated from, like, abstract thinking, complex vision, and language.

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This is the first time I saw someone say this, can you explain more? Does the “old brain” here refer to the brainstem or something else? Why is its functions not complicated?

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Hippocampus/entorhinal cortex, amygdala, hypothalamus, thalamus, basal ganglia, various other bits and bobs of the brain stem?
I have been studying this stuff for years and I can’t figure it out; I am SO ready for someone to explain all this to me.

Sorry, I had to be more specific: hippocampus / entorhinal cortex is an integral part of the neocortex, without it the neocortex is useless, so, even it’s an older part of the brain, I don’t relate it to the ‘lizard brain’.
About the rest, as I mentioned, I’m not saying that this structure is simple or well understood, my point is that is quite easy to get minimum set of functions of all of it, which are important to complete the cortex (with the hippocampus) to the full-fledged intelligence.

I respectfully differ on this.

I see that the Papez circuit loops through most of the limbic system (including the hippocampus) and that the hippocampus is the main mediator between the two systems (limbic and cortex) - it combines the episodic experience and what we felt about it to drive judgement. We do NOT think through what is good and bad about things, we feel it first and remember it with the experience. This ranges from simple objects to complex social settings. Our judgments of good and bad are the accumulation of a multitude of impressions, good and bad, about everything we have ever experienced. The few cases of humans without a functional amygdala (a huge contributor to efferents to the hippocampus) show a profound lack of judgement. You do NOT want a powerful AGI that is not able to exercise good judgement. Some artificial replacement would likely be so alien that humans would have a very hard time understanding why it did anything.

LIkewise, the lower-frontal-lobe is driven with efferents from the hypothalamus. You can say a lot of things about cortex but one of them is NOT that it initiates actions. Cortex is passive. The sensory stream and the motivation/action drives all originate from outside the cortex. The sensory part is self-evident, the forbrain part is the hypothalamus after it experiences whatever is signaled up the brainstem and by taps in various parts of the cortex - primarily the temporal lobe.

The cerebellum does coordinate action going down the brainstem to the body but for humans, serves the very important function of driving the unfolding of activation in the forbrain that is routed back to the upper levels of the WHAT/WHERE streams, the bit we normally call thinking. This is also critical to the learned motor actions we call talking, closely related to this thinking bit.

I know that newbie AGI experimenters think that they will just copy the cortex and voila - they will have a functioning AGI - or at the very least - that these subcortical structures are little stubs that they will tack on the fancy cortex. I say that this shows a profound lack of understanding how much of what we are is tied up this these subcortical structures.


I agree with the factual part of what you said but differ in the emphasis of interpretation.
Actually, I exactly do not want an human-level intelligence with all this hardcoded mess people have in the old brain structures, which evolved in many cases for not even currently useless, but harmful environmental context: all these biases, fears, uncontrolled reactions and other dirty shortcuts we have from ancient times.
Our judgments of good and bad is an illusion, another shortcut for a weak mind, everything depends on the context, just not everybody can (or have enough time) unroll it to get the whole picture.
The subcortical structures are not a stub, it’s an interface to the homeostasis control. It can be implemented in a human-like manner as a semi-independent legacy structure with opportunity/tendency to be reduced to the purely animal behaviour, or it can be a very thin API with all needed processing in the core in a cortex-like manner. I definitely prefer the latter.


I agree with your idea. Do you have a list, what features should an independent intelligent algorithm have? In other words, what tasks it can do, compared to human intelligence?

As soon you have cortical-like processing you get it all. With proper input and training, obviously.
Even old brain stuff like emotions: if you have anything to reflect, you can add it your model of the world and associated it with yourself.

I don’t know at all what role the old brain plays in intelligent behavior (such as reasoning, planning, etc.). I am very skeptical about the power of the neocortex. After all, the neocortex looks similar everywhere.:man_shrugging:

You can be skeptical about its power, but you could not write about it without it :wink:

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And it’s the best part of the story :slight_smile:

Bro, you should tell it if you knew …