Textbook Notes (290,000)
CA (170,000)
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PSYB51H3 (300)
Chapter 3

PSYB51H3 Chapter Notes - Chapter 3: Herman Snellen, Angular Distance, Visual Angle


Department
Psychology
Course Code
PSYB51H3
Professor
Matthias Niemeier
Chapter
3

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PSYB51 Chapter 3 Textbook Notes
SPATIAL VISION: FROM SPOTS TO STRIPES
Terms / Concepts
Contrast: The difference in luminance between an object and the background, or between lighter
and darker parts of the same object
Acuity: The smallest spatial detail that can be resolved at 100% contrast
Cycle: For a grating, a pair consisting of one bright bar
Visual Angle: The angle subtended by an object at the retina
Sine Wave Grating: A grating with a sinusoidal luminance profile
Herman Snellen: Constructed a set of block letters for which
the letter as a whole was five times as large as the strokes
that formed the letter
Visual Acuity:
Distance at which a person can just identify the letters
Distance at which a person with “normal” vision can just
identify the letters
Minimum Visible Acuity: Refers to the smallest object that one can detect
Minimum Resolvable Acuity: Refers to the smallest angular separation between neighbouring
objects that one can resolve
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PSYB51 Chapter 3 Textbook Notes
Minimum Recognizable Acuity: Refers to the angular size of the smallest feature that one can
recognize or identify
Minimum Discriminable Acuity: Refers to the angular size of the smallest change in a feature (e.g.,
a change in size, position, or orientation) that one can discriminate
Spatial Frequency: The number of grating cycles (i.e., dark and bright bars) in a given unit of space
Cycles per Degree: The number of grating cycles per degree of visual angle
Sine wave gratings illustrating low (a), medium (b), and high (c) spatial frequencies
Contrast Sensitivity Function (CSF): A function describing how the sensitivity to contrast (defined
as the reciprocal of the contrast threshold) depends on the spatial frequency (size) of the stimulus
Contrast Threshold: The smallest amount of contrast required to detect a pattern
Phrase: The relative position of a grating
Lateral Geniculate Nucleus (LGN): A structure in the thalamus, part of the midbrain, that receives
input from the retinal ganglion cells and has input and output connections to the visual cortex
Magnocellular Layer: Either of the bottom two neuron-containing layers of the lateral geniculate
nucleus, the cells of which are physically larger than those in the top four layers
Parvocellular Layer: Any of the top four neuron-containing layers of the lateral geniculate nucleus,
the cells of which are physically smaller than those in the bottom two layers
Koniocellular Cell: A neuron located between the magnocellular and parvocellular layers of the
lateral geniculate nucleus. This layer is known as the koniocellular layer
Contralateral: Referring to the opposite side of the body (or brain)
Ipsilateral: Referring to the same side of the body (or brain)
Topographical Mapping: The orderly mapping of the world in the lateral geniculate nucleus and the
visual cortex
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