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Discounting the illuminant
Discounting the illuminant Illumination of the visual world tens to be non-uniform, and fluctuates. in order for the visual system to create a consistent perception of color and lightness it must somehow discount fluctuation and gradient in the lighting source.
RELATED TERMS--------------------------------------
Lightness
The perception of reflectance. Related to the perception of an object's surface.
SIMILAR TERMS--------------------------------------
Disc
Shortened terminology for an intervertebral disc, a disk-shaped piece of specialized tissue that separates the bones of the spinal column.
Disc prolapse
Condition in which an intervertebral disc is damaged and some of it protrudes. May cause sciatica if it does so in the vicinity of a major nerve in the spine.
Disc, cervical
A disk shaped piece of specialized tissue that separates the vertebral bones of the spinal column in the neck.
Disc, optic
The circular area in the back of the inside of the eye where the optic nerve connects to the retina. Also called the optic nerve head.
Disc, slipped
Rupturing of the tissue that separates the vertebral bones of the spinal column.
Discase
Discase is a prescription or over-the-counter drug which is (or once was) approved in the United States and possibly in other countries. Active ingredient(s): chymopapain.
Discharge
1.The flow of fluid from part of the body, such as from the nose or vagina. 2. The passing of an action potential, such as through a nerve or muscle fiber. 3. The release of a patient from a course of care. The doctor may then dictate a discharge summary.
Discipline
The limits a parent or caregiver sets on a child's behavior for purposes of safety or socialization.
Discoid lupus erythematosus
A round, red, scaling rash on the nose, forehead, cheeks, scalp or other areas of the body. It may be associated with systemic lupus erythematosus.
Disconnection syndrome
Term coined by Norman Geschwind to describe the interruption of information transferred from one brain region to another.
Discordance
1. The presence of any given condition such as HIV in only one member of a couple. 2. In genetics, the presence of a phenotype such as asthma in only one members of a twin pair. 3. In clinical care, lack of agreement between physician and patient.In all sense, disconcordance is as opposed to concordance.
Discordant
1. Showing discordance, lack of agreement. A couple may be discordant for a sexually transmitted infection, with one partner having it and the other not. 2. In transplantation genetics, between different species. A discordant xenograft is a transplant between members of very different species
Discordant couple
A pair of long-term sexual partners in which one has a sexually transmitted infection and the other does not. The CDC has guidelines for counseling discordant couples in which the woman is HIV-infected and her husband is HIV-uninfected.
PREVIOUS AND NEXT TERMS--------------------------------------
Diaplopia
Double vision.
Dichoptic stimulation
When different images are presented to each eye.
Dichromatic color vision
Color vision based on two cone photoreceptor pigments in the retina.
Diffraction
The scattering of rays of light by collision with particles of matter as they pass through a medium such as air or water, or pass by a edge or narrow aperture. Plays a role when the pupil is small.
Direction selectivity
A difference in the response of a cell to a pattern of light moving through it receptive field according to the direction of movement. Cells respond well when a stimulus moves in one direction and not in the opposite direction.
Discounting the illuminant
Disparity gradient
The ratio of the difference between two feature's disparities and their cyclopean separation. Steeply slanted surfaces have large disparity gradients. Human binocular fusion will only tolerate a disparity gradient of about 1.
Dorsal pathway
One of two theorized systems of visual information processing. Information thought to progress toward the parietal cortex V1-> V2 -> MT -> MST -> STP. Functions in comprehension of spatial arrangement.
Derma
Skin.
Diffuse
Not definitely localized or limited; spread widely through a tissue or substance.
Diphtheritic membrane
A thin coating on the surface of an epithelial lined organ (e.g. intestine) that is composed of necrotic cellular debris, inflammatory cells and fibrin.
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