Antonio Damasio
has proposed that early sensory cortices construct “image space” and that
association cortices construct “dispositional space.” He believes that
association cortex does not hold any imagery itself and that everything we see
in our “mind’s eye” is constructed in sensory cortex alone. I, on the other
hand, believe that association areas are capable of holding imagery that people
consciously experience. In my opinion association cortices hold imagery of
higher-order concepts that are disoriented from spatial mapping or retinotopic
coordinates. The imagery created in association cortex probably embodies
conceptual relationships and perceptually transcendent concerns. Association
areas may hold true imagery in the sense that they can invoke high-level
perceptions of things of which the person can become conscious. Thus, cortical
areas involved in visual processing - from the posterior occipital pole to the
anterior frontal pole – lie together on a continuum with coordinate bound maps
on one side and abstract, conceptual imagery on the other.
Consistent with
Damasio; however, I agree that association areas do not possess all of the
information held in the early sensory cortices that converge upon them. In
other words, the firing of a grandmother neuron in the anterior temporal cortex
alone does not produce a conscious visual depiction of a grandmother in the
mind’s eye. One can probably not visualize a spatial, line-bound image of one’s
grandmother without early visual cortex. The mental imagery of our grandmothers produced by association cortex would be much more abstract and invariant, and may include behavioral predispositions such as the way we feel, act and compose ourselves when we are around our grandmother.
What would
imagery mappings in association areas such as the dlPFC look like? Early visual
areas create retinotopic visual information because the inputs to the cortex
correspond to the geometric arrays of photoreceptors in the retina. The dlPFC
does not contain an objective input geometry that maps directly onto something
real in the environment. Instead, the input, and thus the maps correspond to
the placement and relative orientation of the lower-order projection inputs that
were arranged during the mammalian evolution of the neocortex. Thus, the
question regarding the spatial architecture of higher order thought and its
imagery can only be answered in the future by neurocartographic investigation
of the unique connectional geometry found in higher-order areas.
I believe that
the early visual cortex activation creates vibrant, experiential imagery simply
because it has become correlated with the appearance of this imagery in the
environment. Brain cells create a theatre of the mind because they have “taken
on” certain external properties. If this is true, then imagery must be held
everywhere because each part of the brain has become correlated with some type
of environmentally induced experience. Like the neurons responsible for the
sensations in a phantom limb, early visual neurons “hold” the experiential
properties of experiences with which they have been correlated with in the
past. Surely anterior association areas have also correlated with experiences,
albeit abstract ones. Thus, purporting that association areas do not hold true
imagery is like saying that imagery is held in the “dots” of primary visual
cortex but not in the “contours” of secondary visual cortex. When you imagine
things, from simple objects to abstract concepts, you experience them again
because you fire the same neurons that fire when it was experienced. This
thinking then frames consciousness as a jumbled up reflection of environmental
occurrences. It is fascinating that we are able to construct a cohesive percept
from a hodgepodge aggregate of previously distinct microrepresentations.
The idea that
association areas may hold their own brand of abstractly mapped imagery frames
the brain as a system of interacting modules specializing in mapping different
topographies that are all trying to generate their best interpretation of what
the other modules are doing. Because some of these modules have assemblies that
fire for sustained periods, they are better positioned to direct activity
through time. The dorsolateral PFC is a good example of a module with the
capacity for sustained influence over modules specialized for visual and
auditory processing, whereas an area such as the orbital PFC may direct maps
generated by emotional and reward-related modules. Further research into the
deficits and intact abilities in patients with damaged association cortex may
better elucidate this issue.
I have published an article on this issue that you can read here:
http://www.sciencedirect.com/science/article/pii/S0031938416308289
I have published an article on this issue that you can read here:
http://www.sciencedirect.com/science/article/pii/S0031938416308289
If you found this
interesting, please visit aithought.com. The site delves into my model of
working memory and its application to AI, illustrating how human thought
patterns can be emulated to achieve machine consciousness and
superintelligence. Featuring over 50 detailed figures, the article provides a
visually engaging exploration of how bridging the gap between psychology and
neuroscience can unlock the future of intelligent machines.
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