Chapter 3: Spatial Vision - From Spots to Stripes

Question 1

contrast

Answer 1

The difference in luminance between an object and the background, or between lighter and darker parts of the same object.

Question 2

acuity

Answer 2

The smallest spatial detail taht can be resolved at 100% contrast.

Question 3

cycle

Answer 3

For a grating, a pair consisting of one dark bar and one bright bar.

Question 4

visual angle

Answer 4

The angle subtended by an object at the retina.

Question 5

sine wave grating

Answer 5

A grating with a sinusoidal luminance profile as shown in Figure 3.4a

Question 6

spatial frequency

Answer 6

The number of grating cycles (i.e., dark and bright bars) in a given unit of space.

Question 7

cycles per degree

Answer 7

The number of grating cycles per degree of visual angle.

Question 8

contrast sensitivity function (CSF)

Answer 8

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.

Question 9

contrast threshold

Answer 9

The smallest amount of contrast required to detect a pattern.

Question 10

lateral geniculate nucleus (LGN)

Answer 10

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.

Question 11

magnocellular layer

Answer 11

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.

Question 12

parvocellular layer

Answer 12

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.

Question 13

koniocellular cell

Answer 13

A neuron located between the magnocellular and parvocellular layers of the lateral geniculate nucleus. This layer is known as the koniocellular layer.

Question 14

contralateral

Answer 14

Referring to the opposite side of the body (or brain).

Question 15

ipsilateral

Answer 15

Referring to the same side of the body (or brain).

Question 16

topographical mapping

Answer 16

The orderly mapping of the world in the lateral geniculate nucleus and the visual cortex.

Question 17

primary visual cortex (V1), area 17, striate cortex

Answer 17

The area of the cerebral cortex of the brain that receives direct inputs from the lateral geniculate nucleus, as well as feedback from other brain areas.

Question 18

cortical magnification

Answer 18

The amount of cortical area (usually specified i millimeters) devoted to a specific region (e.g., 1 degree) in the visual field.

Question 19

visual crowding

Answer 19

The deleterious effect of clutter on peripheral object recognition.

Question 20

orientation tuning

Answer 20

The tendency of neurons in striate cortex to respond optimally to certain orientations and less to others.

Question 21

filter

Answer 21

An acoustic, electrical, electronic, or optic device, instrument, computer program, or neuron that allows the passage of some range of parameters (e.g., orientations, frequencies) and blocks the passage of others.

Question 22

ocular dominance

Answer 22

The property of the receptive fields of striate cortex neurons by which they demonstrate a preference, responding somewhat more rapidly when a stimulus is presented in one eye than when it is presented in the other.

Question 23

simple cell

Answer 23

A cortical neuron whose receptive field has clearly defined excitatory and inhibitory regions.

Question 24

complex cell

Answer 24

A cortical neuron whose receptive field does not have clearly defined excitatory and inhibitory regions.

Question 25

end stopping

Answer 25

The process by which a cell in the cortex first increases its firing rate as the bar length increases to fill up its receptive field, and then decreases its firing rate as the bar is lengthened further.

Question 26

column

Answer 26

A vertical arrangement of neurons. Neurons within a single column tend to have similar receptive fields and similar orientation preferences.

Question 27

hypercolumn

Answer 27

A 1-millimeter block of striate cortex containing two sets of columns, each covering every possible orientation (0-180 degrees), with one set preferring input from the left eye and one set preferring input from the right eye.

Question 28

cytochrome oxidase (CO)

Answer 28

An enzyme used to reveal the regular array of "CO blobs" which are spaced about 0.5 millimeter apart in the primary visual cortex.

Question 29

adaptation

Answer 29

A reduction in response caused by prior or continuing stimulation.

Question 30

tilt aftereffect

Answer 30

The perceptual illusion of tilt, produced by adaptation to a pattern of a given orientation.

Question 31

spatial-frequency channel

Answer 31

A pattern analyzer, implemented by an ensemble of cortical neurons, in which each set of neurons is tuned to a limited range of spatial frequencies.

Question 32

critical period

Answer 32

A phase in the life span during which abnormal early experience can alter normal neuronal development.

Question 33

amblyopia

Answer 33

A developmental disorder characterized by reduced spatial vision in an otherwise healthy eye, even with proper correction for refractive error. Also known as lazy eye.

Question 34

strabismus

Answer 34

A misalignment of the two eyes such that a single object in space is imaged on the fovea of one eye and on a nonfoveal area of the other (turned) eye.

Question 35

anisometropia

Answer 35

A condition in which the two eyes have different refractive errors (e.g., one eye is farsighted and the other not).