Ibotenic Acid

Substance used in lesion studies. Destroys cell bodies of neurons but leave axons in tact.

Iconic Memory

Short-lived visual sensory memory which lasts about 500 msec. Disrupted by masking (i.e. by a bright light). Tied to anatomical coordinates.
(See also Short-Term Visual Store).

Illuminance

Amount of light falling onto an surface. (See also Luminance).

Illusions, Visual

Illusory Contours

Contours which can be perceived in the absence of any real lines or edges. (See also Ehrenstein Illusion). (More on Optical Illusions)

Induction, Brightness

Inner Nuclear Layer

(See Retinal Layers).

Inner Plexiform Layer

(See Retinal Layers).

Interblobs

(See Appendix I: Cortical Areas, V1).

Interferometry

(See Visual Interferometry).

Interocular Motion Display

A motion display in which the motion stimulus in each eye of the observer is ambiguous, yet perception of coherent motion is possible if the subject combines motion information from both the eyes.

Intrinsic Images

A proposal put forward by Barrow and Tenebaum (1978) in which the visual system maintains several representations of the visual scene including lightness, illumination, depth etc. and the user can access each individual representation separate from the others. (See also Workshop Metaphor).

Intrinsic Terminators

(See Terminators)

Isoluminant

Stimuli in which information based on luminance contrast is eliminated and only differences in wavelength are present.

Isomorphistic Approach

Belief that perceptual variations in the visual filed must be accounted for by analogous variations of neural activity. Roughly speaking, the neural distribution should look like the percept.

Isotropic

Any process or filter which is not directionally selective or biased. (As opposed to anisotropic).