Midget cells, also known as P cells or P ganglion cells, are a type of retinal ganglion cell (RGC).
They originate in the ganglion cell layer of the retina and project to the parvocellular layers of the lateral geniculate nucleus (LGN).
Axons travel through the optic nerve and optic tract to synapse with parvocellular cells in the LGN.
Named for their small dendritic trees and cell bodies.
Comprise about 80% of RGCs.
Characteristics
Receptive Fields: Circular with antagonistic center and surround, known as spatial opponency.
ON-center: Excited by photons in the center.
OFF-center: Inhibited by photons in the center.
Chromatic Opponency: Often show chromatic opponency with long- and medium-wavelength light.
Example: L-ON midget cell excited by long-wavelength light at the center and inhibited by medium-wavelength light at the surround.
Not all midget cells are chromatically opponent.
Conduction: Slow conduction velocity but responsive to high temporal and low spatial frequencies.
Connections
Receive inputs from a small number of rods and cones.
Often connected to midget bipolar cells, each linked to one cone.
Additional Information
Visual System: Part of the visual system, primarily involved in processing fine visual details due to their connection to the parvocellular pathway which is sensitive to detail and color.
Comparison: Midget cells are smaller compared to other RGCs like parasol cells.
Related Cells
Parasol Cell: Another type of retinal ganglion cell, larger in size.
Bistratified Cell: Another RGC type, involved in different visual processing.
References
Eye, human. Encyclopædia Britannica, 2008.
Le, Wool; Jd, Crook; Jb, Troy; Os, Packer; Q, Zaidi; Dm, Dacey (2018). "Nonselective Wiring Accounts for Red-Green Opponency in Midget Ganglion Cells of the Primate Retina". The Journal of Neuroscience.