Glossary
- Surface interpolation
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The ability of our visual system to reconstruct a continuous surface from incomplete visual inputs using surrounding information.
- Contrast border
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A boundary of a surface generated by spatially discontinuous change (contrast) in brightness or colour. Many neurons in the retina and early visual pathway are sensitive to contrast border.
- Luminance
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The intensity of light emitted from a light source or reflected from a surface that can be measured objectively.
- Achromatic grating
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A visual stimulus consisting of alternating light and dark bars in shades of grey.
- Motion aftereffect
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Also known as the waterfall illusion. Prolonged observation of a moving stimulus leads to an aftereffect in which stationary objects appear to move in the opposite direction.
- Retinotopic
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If a two-dimensional array of neurons in a given area corresponds topographically (in spatial arrangement) to those on the retina, this area is said to have retinotopic organization. Early visual areas have retinotopic organization with different degrees of precision.
- Primary visual cortex
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(Also known as V1 or the striate cortex). The cortical area that is the main recipient of visual information from the retinae (by way of the lateral geniculate nucleus).
- Receptive field
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The area of sensory space in which stimulus presentation leads to the response of a particular sensory neuron.
- V2
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The second tier of visual cortical areas, which is adjacent to V1. V2 consists of three compartments that can be visualized by cytochrome oxidase staining; thick stripe, thin stripe and interstripe.
- V2 thin stripe
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One of three compartments in V2 where many neurons have sensitivity to the colour or brightness of a visual stimulus.
- V3
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The third tier of visual cortical areas, which receives its main visual input from V1 and V2. V3 can be divided into two areas because dorsal and ventral parts of V3 have different connections and cell properties.
- Extrastriate areas
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A belt of visually responsive areas of cortex surrounding the primary visual cortex.
- Binocular rivalry
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A phenomenon that occurs when each of a subject’s eyes is shown a different image. This results in a bistable visual experience. For example, perception of horizontal or vertical bars spontaneously alternates when the two bar types are viewed through different eyes simultaneously.
- Macular degeneration
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A disease of the retina in which the macula, the central part of the retina, degenerates.
- Pointwise representation
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One way to represent surface attributes such as colour is to activate colour-selective neurons that have a small receptive field at each point on a surface. This is an example of pointwise representation.
- Spatial frequency
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A variable determined by the width of stripes on a grating. A grating with low spatial frequency has thick stripes, whereas a grating with high spatial frequency has narrow stripes.
- Pulvinar nucleus
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The pulvinar is a complex of several nuclei in the thalamus that have strong connections with many visual cortical areas.
- Lateral geniculate nucleus
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(LGN). The LGN is a nucleus in the thalamus that acts as a major relay station for visual signals from the retina to area V1. The LGN also receives a massive feedback projection from V1.
- Qualia
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Qualities of conscious perceptual experience, or the ‘raw’ feel of sensation, such as the ‘redness’ of the colour red.
- Depth assignment
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When a retinal image contains multiple surfaces, the depth order of the surfaces is derived by using various monocular as well as binocular visual cues in the image.
- Stereo-image
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A set of two images — one of which is presented to the right eye and the other to the left — that contain binocular stereo-disparity. Different parts of the stereo-image appear to be at different depths.