Random-Dot Kinematogram

(Julesz 1971)

Comprised of successive frames of random texture in each of which there is no perceptive form. However, the dots in a central portion of each pattern are displace by a constant amount from one frame to the next while the background texture remains the same. The dots comprising the central region are seen to move as a whole revealing a boundary between a moving figure and a stationary surround.

Random-Dot Stereogram

A pair of images consisting of a uniform randomly generated texture of dots. No form is recognizable in the pair, but when fused, displacement of textural elements produces the perception of depth. Evidence against the use of monocular contours for stereopsis.

Receptive Field

Area of the retina and visual space that when stimulated produces a change in the response rate of a neuron.
(See also Perceptive Field).


The fraction of incident light that is reflected toward the eye by an object.
(See Figure).

Reflection Densitometry

Technique applied to the living eye to study photopigments. Measures the light reflected from the fundus (i.e. not absorbed by any pigments).


Light-absorbing portion of rhodopsin. The absorption of light causes retinal to change from 11-cis to 11-trans configuration

Retinal Layers

Outer Nuclear Layer

Contains photoreceptors

Inner Nuclear Layer

Contains bipolar, horizontal and amacrine cells

Ganglion Cell Layer

Contains ganglion cells

Outer Plexiform Layer

Contains processes of receptor, bipolar and horizontal cells

Inner Plexiform Layer

Contains processes of bipolar, amacrine and ganglion cells

Retinex Theory

(Land & McCann 1971)

Theory of lightness and color perception. Argues that the color of an object is not determined by the composition of the light coming from the object. The color of a unit area is determined by a trio of numbers each computed on a single waveband to give the relationship for the waveband between the unit area and the rest of the unit areas in a visual scene.

Retinitis Pigmentosa

A degeneration of the retinal pigment epithelium. This is a single celled layer of pigment cells that is between the retina and the choroid, the second "coat" of the eye. In this condition pigment granules are lost from the epithelium layer and deposited in clumps in the retina. Results in constricted visual fileds and eventraully reduced central vision and blindness. Effects primarity the rods.

Retinotectal Pathway

Pathway from the retina to superior colliculi.

Retinotopic Map

A preservation of the spatial relationships of the photoreceptors in the retina in a higher brain representation.

Reverse Contrast Kanizsa Square

(See Kanizsa Square).


The visual pigment in rod cells. Contains opsin and retinal.

Right Visual Hemifield

The right half of the visual field, projects on the nasal hemiretina of the right eye and on the temporal hemiretina of the left eye.


Binocular Rivalry

When two different images are presented to the two eyes simulataneously, a mosaic-like percept can be obtained, in which different regions of the image correspond to left and right eye images.

Monocular Rivalry


Photoreceptor for dim light conditions. Achromatic, lower acuity and temporal resolution than cones, outnumber cones 20 to 1. Rod system is convergent (many rods target one bipolar cell). (See also Cone).