giant retinal ganglion cells giant retinal ganglion cells giant retinal ganglion cells are photosensitive ganglion cells with large dendritic trees discovered in the human and macaque retina by dacey et al. (2005). giant retinal ganglion cells contain a photo-pigment, melanopsin, allowing them to respond directly to light. they also receive connections from rods and cones, allowing them to encode colour and spatial information. dacey et al. found the giants' receptive field sizes to be about three times the diameter of those of parasol ganglion cells. when a giant is responding directly to light, dacey et al. found its spectral sensitivity function to be similar in shape to those of rods and cones, but with a peak at 482 nm, in between s cones and rods. dacey et al. also found giants' dynamic range to be 3-4 log units, far larger than any other photoreceptor type's and covering nearly the entire range of illuminations of natural daylight. under naturalistic lighting conditions, responses to the rods and cones are superimposed on the melanopsin response of giant retinal ganglion cells. giants encode colour via an s-off, (l + m)-on opponency. their spatial modulation transfer function is low-pass, with an upper limit of about 0.6 cycles per degree. dacey et al. propose that the giants subserve the subconscious, 'non-image-forming' functions of circadian photoentrainment and pupillary diameter, and via the rod and cone inputs, may help mediate conscious perception of irradiance. anatomy of the globe of the human eyefibrous tunic (outer)sclera episcleral layer schlemm's canal trabecular meshwork cornea limbus layers epithelium bowman's stroma dua's layer descemet's endothelium 1:posterior segment 2:ora serrata 3:ciliary muscle 4:ciliary zonules 5:schlemm's canal 6:pupil 7:anterior chamber 8:cornea 9:iris 10:lens cortex 11:lens nucleus 12:ciliary process 13:conjunctiva 14:inferior oblique muscule 15:inferior rectus muscule 16:medial rectus muscle 17:retinal arteries and veins 18:optic disc 19:dura mater 20:central retinal artery 21:central retinal vein 22:optic nerve 23:vorticose vein 24:bulbar sheath 25:macula 26:fovea 27:sclera 28:choroid 29:superior rectus muscle 30:retinauvea / vascular tunic (middle)choroid capillary lamina of choroid bruch's membrane sattler's layer ciliary body ciliary processes ciliary muscle pars plicata pars plana iris stroma pupil iris dilator muscle iris sphincter muscle retina (inner)layers inner limiting membrane nerve fiber layer ganglion cell layer inner plexiform layer inner nuclear layer outer plexiform layer outer nuclear layer external limiting membrane layer of rods and cones retinal pigment epithelium cells photoreceptor cells (cone cell, rod cell) → (horizontal cell) → bipolar cell → (amacrine cell) → retina ganglion cell (midget cell, parasol cell, bistratified cell, giant retina ganglion cells, photosensitive ganglion cell) → diencephalon: p cell, m cell, k cell, muller glia other macula perifoveal area parafoveal area fovea foveal avascular zone foveola optic disc optic cup ora serrata anatomical regions of the eyeanterior segment adnexa (eyebrow, eyelid, conjunctiva, lacrimal system, orbit) fibrous tunic anterior chamber aqueous humour iris posterior chamber ciliary body lens capsule of lens zonule of zinn posterior segment vitreous chamber vitreous body retina choroid other keratocytes ocular immune system optical coherence tomography eye care professional eye disease refractive error accommodation physiological optics visual perception this article is issued from wikipedia. the text is licensed under creative commons - attribution - sharealike. additional terms may apply for the media files.