Chapter 6

Question 1

Fovea

Answer 1

An indentation, about 0.33 centimeter in diameter, at the center of the retina.

The area of the retina that is specialized for high-acuity vision (for seeing fine details).

Question 2

Ciliary muscles

Answer 2

The eye muscles that control the shape of the lenses.

Question 3

Rods

Answer 3

The visual receptors in the retina that mediate achromatic, low-acuity vision under dim light.

Question 4

Cones

Answer 4

The visual receptors in the retina that mediate high acuity color vision in good lighting.

Question 5

Acuity

Answer 5

The ability to see the details of objects.

Question 6

Receptors

Answer 6

Cells that are specialized to receive chemical, mechanical, or radiant signals from the environment; also proteins that contain binding sites for particular neurotransmitters.

Question 7

Binocular disparity

Answer 7

The difference in the position of the retinal image of the same object on the two retinas.

Question 8

Horizontal cells

Answer 8

Type of retinal neurons whose specialized function is lateral communication.

Question 9

Bipolar cells

Answer 9

Bipolar neurons that form the middle layer of the retina.

Question 10

Amacrine cells

Answer 10

A type of retinal neurons whose specialized function is lateral communication.

Question 11

Retinal ganglion cells

Answer 11

Retinal neurons whose axons leave the eyeball and form the optic nerve.

Question 12

Duplicity theory

Answer 12

The theory that cones and rods mediate photopic and scotopic vision, respectively.

Question 13

Photopic vision

Answer 13

Cone mediated vision, which predominates when lighting is good.

Question 14

Scotopic vision

Answer 14

Rod mediated vision, which predominates in dim light.

Question 15

Rhodopsin

Answer 15

A G-protein-coupled receptor that responds to light rather than to neurotransmitter molecules.

Question 16

On-center cells

Answer 16

Respond to lights shone in the central region of their receptive fields with “on” firing and to lights shone in the periphery of their receptive fields with inhibition, followed by “off” firing when the light is turned off.

Question 17

Trichromats

Answer 17

Most primates are trichromats (possessing three color vision photopigments).

Most other mammals are dichromats (possessing two color vision photopigments).

Question 18

Color constancy

Answer 18

Refers to the fact that the perceived color of an object is not a simple function of the wavelengths reflected by it (no matter what light is reflecting from an object, it will stay the same color).

Question 19

Mondrian

Answer 19

The multicolored test. Called Mondrian because they resemble the paintings of Dutch artist Piet Mondrian.

Question 20

Contrast enhancement

Answer 20

The intensification of the perception of edges.

Question 21

Lateral inhibition

Answer 21

Inhibition of adjacent neurons or receptors in a topographic array.

Question 22

Receptive field

Answer 22

The area of the visual field within which it is possible for the appropriate stimulus to influence the firing of a visual neuron.

Question 23

Monocular

Answer 23

Involving only one eye.

Question 24

Iris

Answer 24

The donut-shaped bands of contractile tissue which gives our eyes their characteristic color.

Question 25

Pupil

Answer 25

Hole in the iris.

Question 26

Lens

Answer 26

Behind the iris; focuses incoming light on the retina.

Question 27

Amacrine and horizontal cells are specialized for ____________.

Answer 27

lateral communication

Question 28

Surface interpolation

Answer 28

The process by which we perceive surfaces; the visual system extracts information about edges and from it infers the appearance of large surfaces.

Question 29

Purkinje effect

Answer 29

In intense light, red and yellow wavelengths look brighter than blue or green wavelengths of equal intensity; in dim light, blue and green wavelengths look brighter than red and yellow wavelengths of equal intensity.

Question 30

Saccades (sah-KAHDS)

Answer 30

Small jerky movements, or flicks.

Involuntary fixational eye movements are of three kinds: tremor, drifts, and saccades.

Question 31

Visual transduction

Answer 31

The conversion of light to neural signals by the visual receptors.

Question 32

Retina-geniculate-striate pathways

Answer 32

Conduct signals from each retina to the primary visual cortex, or striated cortex, via the lateral geniculate nuclei of the thalamus.

Question 33

Lateral geniculate nuclei

Answer 33

The six-layered thalamic structures that receive input from the retinas and transmit their output to the primary visual cortex.

Question 34

Mach bands

Answer 34

Mach bands is an optical illusion named after the physicist Ernst Mach. It exaggerates the contrast between edges of the slightly differing shades of gray, as soon as they contact one another, by triggering edge-detection in the human visual system.

Question 35

Primary visual cortex

Answer 35

The area of the cortex that receives direct input from lateral geniculate nuclei (also called striated cortex).

The primary visual cortex (V1) is located in and around the calcarine fissure in the occipital lobe. Each hemisphere’s V1 receives information directly from its ipsilateral lateral geniculate nucleus that receives signals from the contralateral visual hemifield

Question 36

Retinotopic

Answer 36

Organized, like the primary visual cortex, according to a map of the retina.

(Though it has a disproportionate representation of the fovea)

Question 37

Simple cells

Answer 37

Neurons in the visual cortex that respond maximally to straight-edge stimuli in a certain position and orientation.

Question 38

Complex cells

Answer 38

Neurons in the visual cortex that respond optimally to straight-edge stimuli in a certain orientation in any part of their receptive field.

Question 39

Opponent-process theory

Answer 39

The theory that a visual receptor or a neuron signals one color when it responds in one way (e.g., by increasing its firing rate) and signals the complimentary color when it responds in the opposite way (e.g., by decreasing its firing rate).

Question 40

Component theory

Answer 40

The theory that the relative amount of activity produced in three different classes of cones by light determines its perceived color (also called trichromatic theory).

Question 41

Parvocellular layers

Answer 41

The layers of the lateral geniculate nuclei that are composed of neurons with small cell bodies; the top four layers (also called P layers).

Composed of neurons with small cell bodies (parvo means small).

Particularly responsive to color, fine pattern details, and stationary or slowly moving objects.

Cones proved majority of input to P layers.

Question 42

Magnocellular layers

Answer 42

The layers of the lateral geniculate nuclei that are composed of neurons with large cell bodies; the bottom two layers (also called M layers).

Composed of neurons with large cell bodies (mango means large).

Particularly responsive to movement.

Rods proved majority of input to M layers.

Question 43

Prestriate cortex

Answer 43

The band of tissue in the occipital lobe that surrounds the primary visual cortex.

Question 44

Inferotemperal cortex

Answer 44

The cortex of the inferior temporal lobe.

Question 45

Posterior parietal (association) cortex

Answer 45

An area of association cortex that receives input from the visual, auditory, and somatosensory systems and is involved in the perception of spatial location and guidance of voluntary behavior.

(Top)

Question 46

Secondary visual cortex

Answer 46

Areas of cortex that receives most of their input from the primary visual cortex

Question 47

Visual association cortex

Answer 47

Areas of cortex that receive input from areas of secondary visual cortex as well as from the secondary areas of other sensory systems.

Question 48

Most areas of secondary visual cortex are located in two general regions: in the ______ cortex and in the ___________ cortex.

Answer 48

Prestriate; inferotemperal.

Question 49

Damage to an area of the primary visual cortex produces a/n __________ in the corresponding area of the contralateral visual field of both eyes.

Answer 49

Scotoma (an area of blindness)

Question 50

Perimetry test

Answer 50

Dots of light flash various parts of the vision. Patient presses when sees the dot. Locates areas of blindness (scotoma).

Question 51

Blindsight

Answer 51

A phenomenon displayed by patients with scotoma a resulting from damage to primary visual cortex.

The ability of such patients to respond to visual stimuli in their scotomas even though they have no conscious awareness of the stimuli.
(Like continually guessing the right number though it’s shown in area of scotoma)

Question 52

Dorsal stream

Answer 52

Flows from the primary visual cortex to the dorsal prestriate cortex to the posterior parietal cortex.

Most visual cortex neurons in the dorsal stream respond most robustly to spatial stimuli, such as those indicating the location of objects or their direction of movement.

Question 53

Ventral stream

Answer 53

Flows from the primary visual cortex to the ventral prestriate cortex to the inferotemperal cortex.

Most neurons in the ventral stream respond to the characteristics of objects, such as color and shape.

There are clusters of visual neurons in the ventral stream, and each cluster responds specifically to a particular class of objects- for example, faces, bodies, letters, animals, or tools.