Parasol cell

A parasol cell, sometimes called an M cell or M ganglion cell, is one type of retinal ganglion cell located in the ganglion cell layer of the retina. These cells project to magnocellular cells in the lateral geniculate nucleus of the thalamus as part of the magnocellular pathway in the visual system. They have large cell bodies, large branching dendrite networks, and fast conduction velocities. They are innervated by large receptive fields, but receive no information about color. Parasol ganglion cells contribute information about the motion and depth of objects to the visual system.

Parasol ganglion cells are the first step in the magnocellular pathway of the visual system. They project from the retina via the optic nerve to the two most ventral layers of the lateral geniculate nucleus of the thalamus, to the magnocellular cells.

Eventually, the information these cells collect in the retina is sent to various parts of the visual cortex, including the posterior parietal cortex and area V5 through the dorsal stream, and the inferior temporal cortex and area V4 through the ventral stream.

Parasol ganglion cells are located in the retina of the eyes, and make up roughly 10% of all retinal ganglion cells. They have large bodies with extensive, overlapping branched dendrites, and thick, heavily myelinated axons. These properties allow parasol cells to conduct signals very quickly, much faster than the midget cells that feed the P pathway.

Parasol ganglion cells collect information from large receptive fields, containing both rods and cones. Despite the input from cones, parasol ganglion cells do not receive information about color. Unlike midget cells, parasol cell receptive fields contain the same color-type of cones in both their center and surround regions. Due to this lack of specificity, parasol cells cannot differentiate between different light wavelengths reflected from a specific object, and thus can only send achromatic information.

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