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How is the visual field mapped in the occipital lobe?

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Diagram comparing action potential conduction in myelinated and unmyelinated axons, showing a neuron with labeled cell body, myelin sheath, nodes of Ranvier, and the flow of electrical signals along each type of axon. — nervous system In a myelinated axon, the myelin sheath prevents the local current (small black arrows) from flowing across the membrane. This forces the current to travel down the nerve fibre to the unmyelinated nodes of Ranvier, which have a high concentration of ion channels. Upon stimulation, these ion channels propagate the action potential (large green arrows) to the next node. Thus, the action potential jumps along the fibre as it is regenerated at each node, a process called saltatory conduction. In an unmyelinated axon, the action potential is propagated along the entire membrane, fading as it diffuses back through the membrane to the original depolarized region.

The visual field is mapped in the occipital lobe through a process known as retinotopic mapping. In the primary visual area (V1), also called the striate cortex, points in the visual image are laid out across the cortex in a spatial arrangement that corresponds to their layout on the retina.1

This mapping is not a perfect, uniform scale; it is distorted, with a disproportionately large area of the cortex devoted to the fovea and its immediate vicinity to provide higher resolution for the center of the visual field.1

Key features of this organization include:
* Ocular Dominance Columns: Because the two eyes are represented separately, they are organized into a series of "ocular dominance columns" that appear as curving stripes across the cortex.1
* Orientation Columns: Neurons are grouped into columns that respond to specific orientations of lines and edges in the visual field.1
* Blobs: Color information is processed in small, circular patches known as "blobs" located within the orientation column system.1

This retinotopic organization is preserved in other visual areas beyond V1, allowing the brain to maintain spatial information as it processes different features like motion, color, and form.1