Chapter 3: Sensory systems and Perception: Vision

Question 1

prosopagnosia

Answer 1

inability to recognize faces; usually associated with lesions of the right inferior temporal cortex

Question 2

sensory adaptation

Answer 2

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 3

acuity

Answer 3

ability of a sensory system to accurately discriminate spatial detail; usually tested by the ability to spatially discriminate 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 4

saccade

Answer 4

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

Question 5

fovea

Answer 5

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 6

primary visual pathway

Answer 6

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 7

lateral geniculate nucleus

Answer 7

thalamic nucleus that relays information from the retina to the cerebral cortex

Question 8

magnocellular system

Answer 8

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

Question 9

parvocellular system

Answer 9

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

Question 10

primary visual cortex/ striate cortex/ V1

Answer 10

cortex in the calcarine fissure of the parietal lobe that receives visual input from the thalamus

Question 11

extrastriate visual cortical area

Answer 11

regions of the visual cortex that lie outside the primary (striate) visual cortex; includes higher-order visual processing areas such as V4, MT, and MST

Question 12

cortical association areas/ association cortices

Answer 12

regions of cerebral neocortex that are not involved in primary sensory or motor processing

Question 13

V4

Answer 13

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

Question 14

MT (middle temporal)

Answer 14

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

Question 15

MST (middle superior temporal)

Answer 15

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

Question 16

ventral stream

Answer 16

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

Question 17

dorsal stream

Answer 17

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

Question 18

topography

Answer 18

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

Question 19

topographical mapping

Answer 19

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

Question 20

cortical magnification

Answer 20

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 21

cortical modules/ cortical columns

Answer 21

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

Question 22

receptive field

Answer 22

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

Question 23

single-unit recording

Answer 23

method of studying the activity of single neurons using a microelectrode

Question 24

tuning curve

Answer 24

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 25

lightness

Answer 25

in vision, the apparent reflectance of a surface

Question 26

brightness

Answer 26

technically, the apparent intensity of a source of light; more generally, a sense of the effective overall intensity of a light stimulus

Question 27

luminance

Answer 27

physical measure of light intensity

Question 28

simultaneous lightness/brightness contrast

Answer 28

ability of contextual information to alter the perception of a visual target, especially in regard to its luminance (i.e., lightness or brightness; simultaneous brightness contrast) or its color (simultaneous color contrast)

Question 29

illumination

Answer 29

light that falls on a scene or surface

Question 30

reflectance

Answer 30

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 31

transmittance

Answer 31

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

Question 32

inverse optics problem

Answer 32

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

Question 33

color

Answer 33

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

Question 34

color space

Answer 34

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 35

trichromat

Answer 35

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

Question 36

dichromat

Answer 36

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

Question 37

color contrast

Answer 37

different color appearance of surfaces despite similar spectral returns from them

Question 38

color constancy

Answer 38

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

Question 39

cerebral achromatopsia

Answer 39

loss of color vision as a result of damage to the visual cortex

Question 40

form

Answer 40

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

Question 41

depth

Answer 41

in vision the perception of distance from the observer

Question 42

monocular

Answer 42

pertaining to one eye

Question 43

binocular

Answer 43

pertaining to both eyes

Question 44

monocular depth perception

Answer 44

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

Question 45

occlusion

Answer 45

blocked view of distant objects by nearer objects

Question 46

motion parallax

Answer 46

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

Question 47

stereopsis/ binocular depth perception

Answer 47

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

Question 48

retinal disparity

Answer 48

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

Question 49

cyclopean fusion

Answer 49

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

Question 50

binocular rivalry

Answer 50

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 51

motion

Answer 51

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

Question 52

aperture problem

Answer 52

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

Question 53

apparent motion

Answer 53

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

Question 54

motion aftereffect

Answer 54

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

Question 55

fusiform face area

Answer 55

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