Cheers for the post, I find the whole series fascinating.
One thing I was particularly curious about is how these ‘proposals’ are made. Do you have a picture of what kind of embedding is used to present a potential action?
For example, is a proposal encoded in the activations of set of neurons that are isomorphic to the motor neurons and it could then propose tightening a set of finger muscles through specific neurons? Or is the embedding jointly learned between the two in some large unstructured connection, or smaller latent space, or something completely different?
The least-complicated case (I think) is: I (tentatively) think that the hippocampus is more-or-less a lookup table with a finite number of discrete thoughts / memories / locations / whatever (the type of content in different in different species), and a “proposal” is just “which of the discrete things should be activated right now”.
A medium-difficulty case is: I think motor cortex stores a bunch of sequences of motor commands which execute different common action sequences. (I’m a believer in the Graziano theory that primary motor cortex, secondary motor cortex, supplementary motor cortex, etc. etc., are all doing the same kind of thing and should be lumped together.) The exact details of the data structures that the brain uses to store these sequences of motor commands are controversial and I don’t want to get into it here…
Then the hardest case is the areas that “think thoughts”, spawn new ideas, etc., all the cool stuff that leads to human intelligence. (e.g. dorsolateral prefrontal cortex I think.) Things like “I’m going to go to the store” or “what if I differentiate both sides of the equation?”. Those things are clearly not isomorphic to a sequence of motor commands. It’s higher-level than that. Again, the exact data structures and algorithms involved in representing and searching for these “thoughts” is a very big and controversial topic that I don’t want to get into here…
Cheers for the post, I find the whole series fascinating.
One thing I was particularly curious about is how these ‘proposals’ are made. Do you have a picture of what kind of embedding is used to present a potential action?
For example, is a proposal encoded in the activations of set of neurons that are isomorphic to the motor neurons and it could then propose tightening a set of finger muscles through specific neurons? Or is the embedding jointly learned between the two in some large unstructured connection, or smaller latent space, or something completely different?
The least-complicated case (I think) is: I (tentatively) think that the hippocampus is more-or-less a lookup table with a finite number of discrete thoughts / memories / locations / whatever (the type of content in different in different species), and a “proposal” is just “which of the discrete things should be activated right now”.
A medium-difficulty case is: I think motor cortex stores a bunch of sequences of motor commands which execute different common action sequences. (I’m a believer in the Graziano theory that primary motor cortex, secondary motor cortex, supplementary motor cortex, etc. etc., are all doing the same kind of thing and should be lumped together.) The exact details of the data structures that the brain uses to store these sequences of motor commands are controversial and I don’t want to get into it here…
Then the hardest case is the areas that “think thoughts”, spawn new ideas, etc., all the cool stuff that leads to human intelligence. (e.g. dorsolateral prefrontal cortex I think.) Things like “I’m going to go to the store” or “what if I differentiate both sides of the equation?”. Those things are clearly not isomorphic to a sequence of motor commands. It’s higher-level than that. Again, the exact data structures and algorithms involved in representing and searching for these “thoughts” is a very big and controversial topic that I don’t want to get into here…