Vision is in the Brain of the Beholder – Part 3


In Part 1 we introduced the new book by Dr. Eric Kandel featuring the Brain of the Beholder concept, and in Part 2 the influence of Dr. Tom Albright on its elaboration.  Kandel offers the following model:

Kandel Image

The optics of the anterior portion of the eye focuses incoming light reflected from objects in the real word onto the retina in the form of a crude image that is deconstructed into electrical signals.  These “bottom-up” signals, constituting sensation, move through the brain and are recoded based on Gestalt rules of organization and prior experiences.  This coding is orchestrated by “top-down” influences from upstream areas of the visual system distal to the eye, reconstructing information from the eye into the images that we perceive.  Kandel’s reference to deconstructing and reconstructing visual information is consistent with the optometric pioneer Al Sutton’s model of how we build our visual space world.

Sutton Cover

Kandel then references Albright, Purves, and other vision researchers who address what is known as the Inverse Optics Problem.  This has been defined as the problem of retrieving all of the visual information about the 3D environment (the distal stimulus) using only the more limited information contained in the 2D image (the proximal stimulus) projected on the retina of the eye.

Figure 1 Final - size

As Purves and colleagues note in a marvelous review article, the brain’s ability to solve the inverse problem serves as the basis for visually guided behavior by limiting if not eliminating ambiguity coming from a 2-D retinal re-presentations of 3-D objects.  As Kandel summarizes, the reason we can usually resolve the ambiguity of a retinal image accurately is because our brain supplies context learned from prior experiences with the world.

If you had to hazard a guess, where in the brain would you say that the synaptic strengthening occurs, supplying this context from prior experiences?  Take a look again at the beautiful image in Part 2 that illustrates associative learning.  Object “A” is associated with Object “B”.  Or action “A” is associated with response “B”.  Kandel supplies his rendering of Albright’s circuits for visual association and recall as follows:

 

Kandel IT Better

Learned associations between paired objects are consolidated in the temporal lobe.  That is the “indirect pathway” that is activated when one is engaged in visualization.  If you listen again to Tom Albright’s delightful interview on The Science Network we referenced in Part 2, you’ll hear him refer to the seminal paper he co-authored with Charlie Gross and colleagues in the Orwellian year of 1984, establishing Inferior Temporal (IT) cortex as a crucial visual integration area.  In more recent terms, IT is a visual portal for the Ventral/What/Parvocellular stream of visual information.  (How about that?  When you guide a patient in visual associative learning, you’re functioning as an IT specialist!)

But the story doesn’t end there, does it.

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