Chapter 3: Sensory Systems and Perception- Vision

Question 1

sensory adaptation

Answer 1

The adjustment of sensory receptors or other elements in a sensory system to different levels of stimulus intensity; allows sensory systems to operate over a wide range of stimulus intensities

Question 2

acuity

Answer 2

The ability of a sensory system to accurately discriminate spatial detail; usually tested by the ability to spatially discriminate between two points, as in the Snellen eye chart exam for vision. Applies to all the sensory systems, but most obviously to vision and somatic sensation.

Question 3

saccades

Answer 3

A ballistic eye movement that changes the point of binocular visual fixation; normally occur at a rate of three to four per second

Question 4

fovea

Answer 4

The area of the human retina specialized for high acuity; contains a high density of cones and few rods. Most mammals do not have a well-defined fovea, although many have an area of central vision (called the area centralis) in which acuity is higher than in more eccentric retinal regions.

Question 5

primary visual pathway

Answer 5

The pathway from the retina via the lateral geniculate nucleus of the thalamus to the primary visual cortex; carries the information that allows conscious visual perception.

Question 6

lateral geniculate nucleus

Answer 6

The thalamic nucleus that relays information from the retina to the cerebral cortex. Compare to medical geniculate nucleus

Question 7

magnocellular system

Answer 7

The component of the primary visual processing pathway that is specialized in part for the perception of motion and other aspects of stimulus change; so named because of the relatively large neurons involved. Compare to parvocellular

Question 8

parvocellular system

Answer 8

The component of the primary visual processing pathway that is specialized in part for the detection of detail and color; so named because of the relatively small size of the neurons involved. Compare magnocellular system.

Question 9

primary visual cortex (striate cortex (V1))

Answer 9

Also called striate cortex or V1. The cortex in the calcarine fissure of the parietal lobe that receives visual input from the thalamus. Compare to extrastriate visual cortical areas.

Question 10

extrastriate visual cortical areas

Answer 10

Regions of the visual cortex that lie outside the primary (striate) visual cortex; include higher order visual processing areas such as V4, MT, and MST.

Question 11

cortical association areas

Answer 11

Also called association cortiices. The regions of cerebral neocortex that are not involved in primary sensory or motor processing.

Question 12

V4

Answer 12

An area of extrastriate visual cortex that is probably important in color vision, although it processes other information as well.

Question 13

MT areas (middle temporal)

Answer 13

In primates, an extrastriate cortical region related to MT that is in part specialized for motion processing.

Question 14

MST areas (middle superior temporal)

Answer 14

In primates, an extrastriate cortical region related to MST that is in part specialized for motion processing.

Question 15

ventral stream

Answer 15

A partially segregated visual processing pathway passing from the primary visual cortex to toward the temporal lobe that is especially pertinent to object recognition. Compare dorsal stream.

Question 16

dorsal stream

Answer 16

A partially segregated visual processing pathway passing from the primary visual cortex through the extrastriate areas to the higher order association cortices of the parietal cortex; thought to be concerned primarily with spatial aspects of visual processing. Compare to ventral stream.

Question 17

topography

Answer 17

In vision, the study of spatial relationships at different levels of the primary visual pathway.

Question 18

topographical mapping

Answer 18

The specification of spatial relationships in the retina and in the other stations of the primary visual pathway.

Question 19

cortical magnification

Answer 19

The disproportionate representation of cortical space according to peripheral receptor density (such as occurs for the central representation of the fovea of the human eye.)

Question 20

cortical modules/ cortical columns

Answer 20

Vertically organized groups of cortical neurons that process the same or similar information; example are ocular dominance columns and orientation columns in the primary visual cortex.

Question 21

receptive field

Answer 21

The region of the receptor surface of a sensory neuron that when stimulated, elicits a response in the neuron being examined.

Question 22

single-unit recordings

Answer 22

A method of studying the activity of single neurons using a microelectrode.

Question 23

tuning curve

Answer 23

The function obtained when a neuron’s receptive field is tested with stimuli at different orientations; its peak defines the maximum sensitivity of the neuron in question.

Question 24

lightness

Answer 24

In vision, the apparent reflectance of a surface. Compare brightness.

Question 25

brightness

Answer 25

Technically, the apparent intensity of a source of light; more generally, a sense of the effective overall intensity of a light stimulus. Compare lightness.

Question 26

luminance

Answer 26

The physical measure of light intensity

Question 27

simultaneous lightness/ brightness contrast

Answer 27

The ability of contextual information to alter the perception of a visual target, especially in regard to its luminance.

Question 28

illumination

Answer 28

The light that falls on a scene or surface.

Question 29

reflectance

Answer 29

The percentage of incident light reflected from a surface (often expressed as the reflectance efficiency function, in which the reflectance of a surface is measured at different wavelengths).

Question 30

transmittance

Answer 30

The percentage of light energy that reaches a detector when passed through a filter.

Question 31

inverse optics problem

Answer 31

The impossibility of knowing the world directly by means of light stimuli; arises because of the ambiguity of light patterns projected into the retina.

Question 32

color

Answer 32

The subjective sensations elicited in humans (and presumably many other animals) by different spectral distributions of light.

Question 33

color space

Answer 33

The depiction of human color experience in diagrammatic form by a space with three axes representing the perceptual attributes of hue, saturation, and color brightness

Question 34

trichromats

Answer 34

A person or other animal whose color vision depends on three retinal cone types that absorb long, medium, and short wavelengths of light, respectively.

Question 35

dichromats

Answer 35

A color-deficient human (and the majority of mammals) whose color vision depends on only two cone types Compare trichromats.

Question 36

color contrasts

Answer 36

The difference color appearance of surfaces despite similar spectral returns from them. Compare color constancy.

Question 37

color constancy

Answer 37

The similar color appearance of surfaces, despite different spectral returns from them; usually applied to the similar appearance of objects under different illuminants. Compare color contrasts.

Question 38

cerebral achromatapsia

Answer 38

Loss of color vision as a result of damage to the visual cortex.

Question 39

form

Answer 39

The perception of object geometry or shape; one of the major visual perceptual qualities

Question 40

depth

Answer 40

In vision the perception of distance from the observer

Question 41

monocular

Answer 41

Pertaining to one eye. Compare binocular

Question 42

binocular

Answer 42

Pertaining to two eye. Compare monocular.

Question 43

monocular depth perception

Answer 43

the sense of three-dimensionality when looking at the world with one eye closed.

Question 44

occlusion

Answer 44

The blocked view of distant objects by nearer objects.

Question 45

motion parallax

Answer 45

The different degree of movement of near and far objects as a function of moving the head or body while observing a scene.

Question 46

binocular depth perception/ stereopsis

Answer 46

The special sensation of depth that results from fusion of the two eyes’ views of relatively nearby objects.

Question 47

retinal disparity

Answer 47

The geometrical difference between he same points in the images projected on the two retinas, measured in degrees with respect to the fovea.

Question 48

cyclopean fusion

Answer 48

The normal sense, when looking at the world with both eyes, that we see it as if with a single eye.

Question 49

binocular rivalry

Answer 49

The bi-stable visual experience that occurs when the right and left eyes are presented with incompatible or conflicting images and visual perception alternates between the two images every few seconds.

Question 50

motion

Answer 50

The changing position of an object defined by speed and direction within a frame of reference.

Question 51

aperture problem

Answer 51

The challenge of determining the speed and direction of a moving line when it ends are obscured by an opening such as a circular hole or a vertical rectangle.

Question 52

apparent motion

Answer 52

The sensation of motion elicited by presentation of a stimulus in two successive positions over a brief interval.

Question 53

motion aftereffects

Answer 53

The persistence of perceived motion in the opposite direction when a motion stimulus has ceased.

Question 54

fusiform face area

Answer 54

A region of the fusiform gyrus that shows enhanced responses to faces relative to other objects.