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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. |
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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. |
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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) |
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 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. |
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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).
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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) |
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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)
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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°).
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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.
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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.
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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.
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The Monocular field that has no pattern and is undefined in direction.
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[ Next : 5.3 Dyslexia and the Primary Visual Cortex (V1) ] |
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