1. Orientation columns not columns (cylindrical in shape)
but slabs (parallel to each other) ! …πλάκες
+ pinwheel formations (where multiple columns converge around a point)*
c, d = orientation maps (subject 1, subject 2)
black lines = ODC borders
*circles = pinwheel centers (white, black = columns converge clockwise, anticlockwise respectively)
b. preferences to R or L eye stimulation
c. preferred stimulus orientation
(Yacoub, Harel & Uğurbil, 2008)

2. Blobs: Groups of neurons that assemble in cylindrical shapes
Sensitive to color
Input-> parvocellular cells in V1 layer 4Cβ
Output-> the thin stripes of area V2
CO rich * Interblobs:
Areas between blobs
Sensitive to orientation
Input-> parvocellular cells in V1 layer 4Cβ (same)
Output-> the pale stripes of area V2
CO deficient
pyramidal cell modules
blobs
cones
(Peters & Setharis, 1991)
CO = Cytochrome Oxidase Integral transmembrane protein, it catalyzes the generation of adenosine triphosphate (ATP). The amount of CO in a cell-> an indicator of cellular activity

3. Hubel, 1995
Hypothetical pattern of activation of striate cortex (left) when a 60° tilted line segment (right) is presented to the left eye
Only left eye and 60° slabs are activated
Activation is confined to a long and narrow cortical area to reflect the shape of the line

4. Tilt illusion
Orientations between 0°  - 50°  -> repulsion effects (grating tends to rotate away from the context)
Orientations up to 90°  -> attraction effects (grating tends to rotate along with the context)

5. Lateral inhibition (Blakemore, 1970)
1. align the two gratings
Explanation?
Lateral inhibition (Blakemore, 1970)
Optimized processing of natural image statistics (Schwartz, 2009) -> does not contradict the inhibition explanation, but puts it into a more Bayesian context
2. invert the background -> gratings no longer aligned
3. no background -> misalignment angle -3.1° !
Demo: