Sensation And Perception: Ch. 3 Spatial Vision

Front 1

Contrast

Back 1

the difference in illumination between an object and the back ground, or between brighter and dimmer parts of the same object.

Front 2

Acuity

Back 2

the smallest spatial detail that can be resolved.

Front 3

Visual angle

Back 3

the angle subtended by an object at the retina.

Front 4

Cycle

Back 4

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

Front 5

Sine wave grating

Back 5

a grating with a sinusoidal luminance profile

Front 6

Aliasing

Back 6

misperception of a grating due to undersampling.

Front 7

Spatial frequency

Back 7

the number of cycles of a grating per unit of visual angle (usually specified in degrees).

Front 8

Cycles per degree

Back 8

the number of dark and bright bars per degree of visual angle.

Front 9

Contrast sensitivity function (CSF)

Back 9

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.

Front 10

Contrast threshold

Back 10

the smallest amount of contrast required to detect a pattern.

Front 11

Phase

Back 11

the relative position of a grating.

Front 12

Lateral geniculate nucleus (LGN)

Back 12

a structure in the thalamus, part of the mid-brain, that receives input from the retinal ganglion cells and has input and output connections to the visual cortex.

Front 13

Magnocellular layers

Back 13

the neurons in the bottom two layers of the lateral geniculate nucleus, which are physically larger than those in the top four layers.

Front 14

Parvocellular layers

Back 14

the neurons in the top four layers of the LGN, which are physically smaller than those in the bottom two layers.

Front 15

Contralateral

Back 15

referring to the opposite side of the body (or brain)

Front 16

Topographical mapping

Back 16

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

Front 17

Primary visual cortex (VI)

Back 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 and is responsible for processing visual information. Also called striate cortex.

Front 18

Cortical magnification

Back 18

the amount of cortical area (usually specified n millimeters) devoted to a specific region in the visual field.

Front 19

Orientation

Back 19

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

Front 20

Filter

Back 20

an acoustic, electric, electronic, or optical device, instrument, computer program, or neuron that allows the passage of some frequencies or digital elements and blocks the passage of others.

Front 21

Ocular dominance

Back 21

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.

Front 22

Simple cell

Back 22

a cortical neuron with clearly defined excitatory and inhibitory regions.

Front 23

Complex cell

Back 23

a neuron whose receptive-field characteristics cannot be easily predicted by mapping with spots of light.

Front 24

End stopping

Back 24

the process by which cells in the cortex first increase their firing rate as the bar length increases to fill up its receptive field, and then decrease their firing rate as the bar is lengthened further.

Front 25

Column

Back 25

a vertical arrangement of neurons.

Front 26

Hypercolumn

Back 26

a 1-mm block of striate cortex containing "all the machinery necessary to look after everything the visual cortex is responsible for, in a certain small part of the visual world". (A hypercolumn contains at least two sets of columns, each of which covers every possible orientation, with one set preferring input from the left eye and one set preferring input from the right eye.)

Front 27

Cytochrome oxidase (CO)

Back 27

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

Front 28

Adaptation

Back 28

a reduction in response caused by prior or continuing stimulation.

Front 29

Tilt aftereffect

Back 29

the perceptual illusion of tilt, produced by adapting to a pattern of a given orientation.

Front 30

Spatial frequency channels

Back 30

pattern analyzers, implemented by ensembles of cortical neurons, with each set of neurons tuned to a limited range of spatial frequencies.

Front 31

Strabismus

Back 31

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