We talked before about the timeline in the brain.
Well, lookie here:
Notice the yellow in figures a, c, and d.
These are maps of the anatomical projections of dopamine neurons in the substantia nigra and ventral tegmental area of the human brain.
You can see the organization along the timeline, it's clear as day.
The substantia nigra (area A8) and ventral tegmentum (areas A9 and A10) are important parts of the egocentric reference frame.
A8 is the one involved in Parkinson's, it's called substantia nigra pars compacta. It is involved in the initiation of voluntary motor movements (and therefore the selection of behavior, which is egocentric in nature). A9 and A10 are the ones involved with the rewarding effects of stimulant drugs, amphetamines, cocaine, like that. Also very egocentric.
A8 maps directly to the superior colliculus, which has an egocentric map of eye position ("gaze"). What happens in SC is a firing neuron will direct the eyes to move to that point in the visual field. The brain says, I want to look at "that", and then it directs the eyes to move to "that" location, which is then translated by downstream neurons into combinations of activity in the oculomotor muscles (lateral, up and down, and lens accommodation).
The egocentric reference frame ("I") is generated by a compactified timeline. It starts with a time mapping based on evoked potentials and premotor potentials -- you can think of it as a linear window of time centered on "now", the current moment. Mathematically it's a line segment whose origin moves along with physical time This construction translates brain activity into time series relative to t=0, which in turns allows the definition of t=0 as the center of the egocentric reference frame.
The egocentric reference frame is the constructed by "compactifying" the timeline interval, which means joining the two ends so the line segment becomes a circle. Mathematically this is called an Alexandroff 1-point compactification, because it involves adding a single point to the interval which is designated as "the point at infinity".
Physicists and computer graphics people will immediately recognize this construction as a projective map, and more specifically an orthographic perspective transformation. Basically we want the camera to live at the point at infinity, so it looks out at the entire timeline, with the greatest resolution at "now".
We previously talked about the ensuing Hawaiian earring, which follows logically from the use of homogeneous coordinates to map the change of basis. In this way, stimulus and response in a neural reflex becomes before and after in the egocentric reference frame.
"I" is a superimposition of all the radii of the Hawaiian earring. Basically what happens is if you're a bug walking along the timeline and you follow an evoked potential when it starts at t=0 and moves off to the left (t<0 direction), eventually you reach the point at infinity, which means the next step you take is going to teleport you to the far right of the timeline (t>0 direction).
In the limit as dt => 0, the point at infinity is defined as memory (the global associative store), because memory is the ultimate destination of all sensory activity, and the ultimate source of all motor activity).
The machine learning types will immediately realize that some support infrastructure is needed to make such a system work in practice, and the good and amazing news is this is exactly what the brain has! If you look for it, it will leap off the page at you. The relationship between the hippocampus and episodic memory is the best studied and best known example. The example in the above pic comes from the opposite side of the timeline, from a brain area called the striatum. It is the part of the brain involved with behavioral selection (and also cognitive selection). You can see very clearly that it's regulating the timeline. What it's specifically doing is filtering the parts of the information it wants to respond to. Part of the response is based on the ongoing sensorimotor activity (that's A8), and part of it is affective and based on the expectation of reward and the determination of which behaviors are most "desirable" (A9 and A10).
The cerebral cortex is an overlay of the timeline with the global associative store. Essentially it "unfolds" the moment called now. In doing so, it uses a section through the plane of Hawaiian earrings of various diameters, from the point at infinity to the point at t=0. To visualize this geometrically we can look at this Hawaiian earring where the point t=0 is on the left and the point at infinity is on the right.
Each diameter of the earring is a neural reflex arc, which equates with a compactified timeline. So for example a big diameter might be the reflex arc from your big toe to your primary sensorimotor cortex, that's a long pathway that defines a large interval along the timeline. Whereas, moving leftward, a smaller diameter might be the reflex arc between your eye and your brain, which is a much shorter pathway defining a smaller interval along the timeline. In the limit as dt=>0, the opening and closing of ion channels based on the configuration of local receptor proteins is a very small interval. If we take a section from the point at infinity to the point at t=0, all intervals are represented, and these points can then be expanded into fiber bundles and math can be done on them - not the least of which is the same kind of stochastic optimization that John Hopfield's neural Ising model accomplishes, which he just got the Nobel prize for.
This is how the brain creates "I", the egocentric reference frame.
Well, lookie here:
Notice the yellow in figures a, c, and d.
These are maps of the anatomical projections of dopamine neurons in the substantia nigra and ventral tegmental area of the human brain.
You can see the organization along the timeline, it's clear as day.
The substantia nigra (area A8) and ventral tegmentum (areas A9 and A10) are important parts of the egocentric reference frame.
A8 is the one involved in Parkinson's, it's called substantia nigra pars compacta. It is involved in the initiation of voluntary motor movements (and therefore the selection of behavior, which is egocentric in nature). A9 and A10 are the ones involved with the rewarding effects of stimulant drugs, amphetamines, cocaine, like that. Also very egocentric.
A8 maps directly to the superior colliculus, which has an egocentric map of eye position ("gaze"). What happens in SC is a firing neuron will direct the eyes to move to that point in the visual field. The brain says, I want to look at "that", and then it directs the eyes to move to "that" location, which is then translated by downstream neurons into combinations of activity in the oculomotor muscles (lateral, up and down, and lens accommodation).
The egocentric reference frame ("I") is generated by a compactified timeline. It starts with a time mapping based on evoked potentials and premotor potentials -- you can think of it as a linear window of time centered on "now", the current moment. Mathematically it's a line segment whose origin moves along with physical time This construction translates brain activity into time series relative to t=0, which in turns allows the definition of t=0 as the center of the egocentric reference frame.
The egocentric reference frame is the constructed by "compactifying" the timeline interval, which means joining the two ends so the line segment becomes a circle. Mathematically this is called an Alexandroff 1-point compactification, because it involves adding a single point to the interval which is designated as "the point at infinity".
Physicists and computer graphics people will immediately recognize this construction as a projective map, and more specifically an orthographic perspective transformation. Basically we want the camera to live at the point at infinity, so it looks out at the entire timeline, with the greatest resolution at "now".
We previously talked about the ensuing Hawaiian earring, which follows logically from the use of homogeneous coordinates to map the change of basis. In this way, stimulus and response in a neural reflex becomes before and after in the egocentric reference frame.
"I" is a superimposition of all the radii of the Hawaiian earring. Basically what happens is if you're a bug walking along the timeline and you follow an evoked potential when it starts at t=0 and moves off to the left (t<0 direction), eventually you reach the point at infinity, which means the next step you take is going to teleport you to the far right of the timeline (t>0 direction).
In the limit as dt => 0, the point at infinity is defined as memory (the global associative store), because memory is the ultimate destination of all sensory activity, and the ultimate source of all motor activity).
The machine learning types will immediately realize that some support infrastructure is needed to make such a system work in practice, and the good and amazing news is this is exactly what the brain has! If you look for it, it will leap off the page at you. The relationship between the hippocampus and episodic memory is the best studied and best known example. The example in the above pic comes from the opposite side of the timeline, from a brain area called the striatum. It is the part of the brain involved with behavioral selection (and also cognitive selection). You can see very clearly that it's regulating the timeline. What it's specifically doing is filtering the parts of the information it wants to respond to. Part of the response is based on the ongoing sensorimotor activity (that's A8), and part of it is affective and based on the expectation of reward and the determination of which behaviors are most "desirable" (A9 and A10).
The cerebral cortex is an overlay of the timeline with the global associative store. Essentially it "unfolds" the moment called now. In doing so, it uses a section through the plane of Hawaiian earrings of various diameters, from the point at infinity to the point at t=0. To visualize this geometrically we can look at this Hawaiian earring where the point t=0 is on the left and the point at infinity is on the right.
Each diameter of the earring is a neural reflex arc, which equates with a compactified timeline. So for example a big diameter might be the reflex arc from your big toe to your primary sensorimotor cortex, that's a long pathway that defines a large interval along the timeline. Whereas, moving leftward, a smaller diameter might be the reflex arc between your eye and your brain, which is a much shorter pathway defining a smaller interval along the timeline. In the limit as dt=>0, the opening and closing of ion channels based on the configuration of local receptor proteins is a very small interval. If we take a section from the point at infinity to the point at t=0, all intervals are represented, and these points can then be expanded into fiber bundles and math can be done on them - not the least of which is the same kind of stochastic optimization that John Hopfield's neural Ising model accomplishes, which he just got the Nobel prize for.
This is how the brain creates "I", the egocentric reference frame.
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