Intro arrow 5. Primary Visual Cortex arrow 5.2 Origin of Patterns
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5.2 Visual Grid and the Origin of Ocular Dominance Patterns in V1


 The Visual Primary Cortex (V1) is build up as a fingerprint-like pattern, the origin of this setup is connectivety optimalisation for processing the input of both eyes. Thanks to "Ocular Dominance" a raster is constructed that gives us grip on what we see.

V1 consists of tiled sets of selective spatio-temporal filters, together they can carry out neuronal processing of spatial frequency, orientation, motion, direction and speed (thus temporal frequency). The visual information relayed to V1 is not coded in terms of spatial (or optical) imagery, but rather as local contrast. For example, an image with one half black and one half white, the separating line has the strongest local contrast and is encoded, while few neurons code the brightness information (black or white). As information is send further to other visual areas, it is coded as increasingly non-local frequency/phase signals, at these early stages of visual processing, spatial location of visual information is well preserved amid the local contrast encoding.

In a few steps I reflect Professor Dmitri B. Chklovskii and Alexei A. Koulakov theory of the origin of these Maps in the brain, as they have reproduced orientation preference maps by minimizing the length of neuronal connections, or wiring. (Source pdf: Orientation preference maps in mammalian visual cortex: A wire length minimization approach)

1. The Retinas project to the Left- and Right hemisphere and their compatible "Ocular Dominance Patters". The full-black region in the LH represents the right monocular (MC) field, the blank region in the RH represents the monocular region to the left: Alpha-regulated.


 2. The Binocular Disparity setup explains how images of the Focus-points are linked in the Primary Visual Cortex (V1), like magnets the points will snap and link easier and faster when they are closer to each other: (a.) Horizontal vs. (b.) Vertical. "Connections are longer if the ocular dominance stripes run orthogonally to the disparity direction (A) than if they run parallel to that direction (B). This finding suggests that the ocular dominance stripes should align with the dominant disparity direction" and "These Ocular Dominance Patterns (ODC) minimize the length of connections in neuronal circuits, which implement binocular stereo-vision." (source: Chklovskii 2000a).


 3. The lay-out of "Wiring Models & Ocular Dominance Patterns" gives an overview of the natural patterns that are formed when the shortest connections (fastest) are made between the left- and right input of the retinas via the LGN to the Primary Visual Cortex (V1).

 

The neurons are organized according to their functional properties into multiple maps such as retinotopic, ocular dominance, orientation preference, direction of motion, and others. What determines the organization of cortical maps? We argue that cortical maps reflect neuronal connectivity in intracortical circuits.

 

Connecting distant neurons requires costly wiring (i.e., axons and dendrites), there is an evolutionary pressure to place connected neurons as close to each other as possible. Then, cortical maps may be viewed as solutions that minimize wiring cost for given intracortical connectivity. These solutions can help us in inferring intracortical connectivity and, ultimately, in understanding the function of the visual system."

(Source: Chklovskii Lab -> Ocular dominance patterns)

 Result: The models show us that when "The Number of Connections With the Same Eye Neurons" (Ns) is bigger then "The Number of Connections With the Opposite Eye Neurons" (No) a "Stripes"-pattern minimizes wiring ( fastest connections ) until "Patches" take over and they are in fact a "Salt & Pepper"-like formation. The image below shows the results of "Chklovskii-theory" (red), compered to the "Ocular Dominance Pattern" (Source pdf)

 4. The "Wiring Model of Ocular Dominance Patterns" functionality of the network required each neuron to make certain numbers of connections with neurons of other categories, instead of having just two categories of neurons Chklovskii's lab introduced several categories of neurons differing by their preferred orientation. This idea is illustrated on the model below, that includes 4 different orientation categories (-45, 0, 45, 90).

 Result: the figures show "The number of intracortical neuronal connections in the Visual Cortex (A)" and the corresponding "Orientation Preference Patterns (B)" obtained by minimizing the length of these connections. Based on these results, professor Mitya propose that the functional significance of pinwheels and fractures may be in minimizing wiring length for certain intracortical connection rules.

 After looking at professor Mitya's theory we can notice that a fluent fluctuation, sinusoid goes together with the striped-pattern: natural.

 

 

 An other conclusion is that this natural flow (transition) is in reverse adjusted to the vertical and horizontal environment around us, created by plants and trees growing towards he sun and the forces of gravity on our planet. We can see this 'grid-like' structure everywhere around us.

 The striped pattern creates a visual grid so we can stay in balance and having grip on our environment, we find guidance, bases, hold-ons in vertical and horizontal elements, where we can let our eyes rest upon.

 

The alignment system is also present in our alphabet, and in the oriental writing systems where text goes from top to bottom. So a good feeling for alignment and assisting Alpha-Area elements that give a strong alingning (see topic: 1.5 Alignment) gives a stronger hold-on/guide to read more relax and have a steady grip on our surroundings.

 


 The Monocular field that has no pattern and is undefined in direction.

 

 

 

 




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