> When one imagines a visual stimuli, does it also register (measurably) as a
> change in the visual part of the brain? I know that they can measure light
> hitting the retina registering in the back of the brain.... Can one "see" the
> process of this kind of imaging ( as is "seeing" a purple walrus" ) in the
> brain _ or trace it to retinal movement ( like in REM) or, more importantly
> induce or improve the abilities to "see" in one's imagination?
I don't think we can image it well yet, but in PET or FMRI scans it is
visible as an activity increase in the visual cortices. Yes, there are
several high-level cortices dealing with vision, and presumably the
purple walrus will exist as activity in some of them. V1 (the "classic"
visual cortex) deals mostly with what we really see (plus what our brain
extrapolates from it), while V2-V5 seem to deal with various aspects of
it (color, movement, edges etc). I think sensory information gradually
gets integrated with general activity in the association cortices, and
very hard to identify.
> For example if one applies stimuli to the visual parts of the brain would it
> help someone "see" the purple walrus who had otherwise no ability to imaging
> visually?
If you applied the right stimuli to V1 the person would see the walrus,
but at higher levels the result would probably be more like suddenly
envisioning it.
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Anders Sandberg Towards Ascension!
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