Hi,
Does HTM have an idea (or some clues) about how egocentric location is computed?
Thank you
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first - this answer involves a lot of hand-waving to cover obvious gaps; please take it as a general approach.
Assuming that the substrate for head direction is based on the posture control system the chart on page 222 in this reference should shed some light on the relationship between the vestibular system and head position:
http://cw.tandf.co.uk/neurophysiology/sample-material/Neurophysiology-5E_Chapter-11.pdf
I will offer that as part of learning your body and it’s limits this chain of relationship continues down though the posture control system which ends up extending to all the positions you can reach with your muscles and sense in a reciprocal responses. In light of this I expect that the “support Pressure Receptors” box to be have many more stages like this chart.
This ego frame of reference starts with your support points and builds up from there through the sensory system.
The origin of this reference system is in relation to your vestibular system; this is why you “live” in your head.
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The cortical column’s circuit must be capable of representing:
- an object and its subcomponents
- where the sensory input relates to motion of the sensor in relation to the object
- an environment and its subcomponents
- where the sensory input relates to the motion of the organism with the environment
#1 above is allocentric, or the “what” pathway. #2 is egocentric, or the “where” pathway. HTM theory says more about the allocentric object recognition part, but maybe there is something to learn there.
An object is learned by associating the movement of sensors with their sensations over it. Think of reaching into a dark box and touching something. As you make that first touch, that sensation is assigned a random location code based on grid cells, and every touch from that point is relative to that location. As you move your sensors over the object, you build out the representation with sensation and movement. Opening your eyes and turning the lights on adds more representations from another sensory area.
You could say that organisms explore their environments in the same way you might explore an unknown item with your eyes and hands.
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This is very interesting. How can a cortical column represent the subcomponents of an object/environment? Also where does it happen?
Do cortical columns in the “where” pathway have the same structure (layers) as cortical columns in the “what” pathway?
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Yes, although there are always some local variations depending on what exactly the area of cortex has decided to do during its life (i.e. your brain is really plastic).
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