Ice Cube Model: Cortical Module
3D Cortical Module
Non-linear Representation of Visual Space
Layering in LGN
Complex Cortical Neuron
Competition for Ocular Dominance
This is the so-called "Ice Cube" model of the visual cortex illustrating cortical architecture. This 1mm by 1mm region of cortex contains all orientations, columns for both the left and right eyes, and blobs. It contains all of the processing machinery for one small region of visual space. This ice cube is repeated over and over again across the visual cortex, and is a prime example of the columnar organization of the cortex.
The foveal region of the cortex is greatly expanded in relation to more peripheral regions.
This slice through the lateral geniculate shows each of the layers. Layers 3-6 are the parvo layers mediating "form' the co-called "what" pathway. Layers 1 and 2 are the "magno" layers mediating "where" activity.
This is a recording from a "complex" cortical cell. It has a specific orientation, responds best to movement of a bar perpendicular to that orientation, but is unresponsive to movement at right angles to the preferred movement. It lacks the center-surround specific regions found in simple cells. This cell is not directionally-selective: it responds to movement in either direction. Turn up the volume and listen to the spikes.
This movie illustrates how inputs from each eye competes for dominance of cortical real estate. When one eye is occluded it loses its competitive advantage so inputs from the other eye begin to spread into the areas originally occupied by the occluded eye. This process can continue through the critical period. It underlies the formation of binocular neurons in the visual cortex.