Chapter 6

Question 1

Light

Answer 1

waves of electromagnetic energy between 380 and 760 naometers

Question 2

Fovea

Answer 2

an indentation
about 0.33 centimeter in diameter, at the center of the retina
it is the area of the retina that is specialized for high-acuity vision (for seeing fine details)

Question 3

Retina

Answer 3

neural component of the eye that contains photoreceptors

Question 4

Sensitivity

Answer 4

the ability to detect the presence of dimly lit objects

Question 5

Acuity

Answer 5

The ability to see the details of objects

Question 6

Binocular Disparity

Answer 6

The difference in the position of the same image on the two retinas

Question 7

Retinal ganglion cells

Answer 7

the output stage of retinal information processing

Question 8

blind spot

Answer 8

the second of the two visual problems created by the inside-out structure of the retina

Question 9

completion

Answer 9

the visual system uses information provided by the receptors around the blind spot to fill in the gaps in your retinal images
when the visual system detects a straight bar going into one side of the blind spot and another straight bar leaving the other side, it fills in the missing bit for you; and what you see is a continuous straight bar, regardless of what is actually there.

Question 10

Photoreceptors: Rods and Cones

Answer 10

Rods - low light levels or scotopic vision
Cones - vision at higher light levels or photonic vision

Question 11

Transduction

Answer 11

the conversion of one form of energy to another
visual transduction is the conversion of light to neural signals by the visual receptors

Question 12

rhodopsin

Answer 12

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

it initiate a cascade of intracellular chemical events when they are activated

Question 13

retina-geniculate-striate pathways

Answer 13

conduct signals from each retina to the primary visual cortex, striate cortex, via the lateral geniculate nuclei of the thalamus

Question 14

primary visual cortex (striate cortex)

Answer 14

Makes up a small portion of the visible surface of the cortex in the occipital lobe
essential to the conscious processing of visual stimuli

Question 15

Lateral geniculate nuclei

Answer 15

nucleus in the thalamus that receives visual information from the retina and sends it to the visual cortex for processing

Question 16

optic chiasm

Answer 16

all signals from the left visual field reach the right primary visual cortex, either ipsilaterally from the temporal hemiretina of the right eye or contralaterally via the optic chiasm

Question 17

contrast enhancement

Answer 17

every edge we look at is highlighted for us by the constrast-enhanceing mechanisms of our nervous systems
- our perception of edges is better than the real thing

Question 18

mach bands

Answer 18

the nonexistent stripes of brightness and darkness running adjacent to the edges

Question 19

lateral inhibition

Answer 19

the second that when a receptor fires, it inhibits its neighbors via the lateral neural network
because it spreads laterally across the array of receptors

Question 20

receptive field

Answer 20

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

Question 21

component theory

Answer 21

proposed by Thomas Young in 1902 and refined by Hermann von Helmholtz in 1852
according to this theory there are three different kinds of color receptors(cones) each with a different spectral sensitivity and the color of a particular stimulus is presumed be encoded by the ratio of activity in the three kinds of receptors

Question 22

opponent process theory

Answer 22

proposed by Ewald Hering
suggested that there are two different classes of cells int he visual system for encoding color and another class for encoding brightness

Question 23

posterior parietal cortex

Answer 23

areas of association cortex that receive visual input are located in several parts of the cerebral cortex, but the largest single area is in the posterior parietal cortex

Question 24

inferotemporal cortex

Answer 24

cortex of the inferior temporal lobe

Question 25

scotoma

Answer 25

an area of blindness

Question 26

conscious awareness

Answer 26

we assume that someone who has seen something will be able to acknowledge that he or she has seen it and be able to describe it
people who see things but have no conscious awareness of them

Question 27

Blindsight

Answer 27

the ability to respond to visual stimuli in a scotoma with no conscious awareness of them

Question 28

Dorsal stream

Answer 28

flows from the primary visual cortex to the dorsal prestriate cortex to the posterior parietal cortex

Question 29

Ventral stream

Answer 29

flows from the primary visual cortex to the ventral prestriate cortex to the inferotemporal cortex

Question 30

where versus what theory

Answer 30

damage to some areas of cortex may abolish certain aspects of vision while leaving others unaffected

most convincing support for the influential “where” versus “what” theory has come from he comparison of the specific effects of damage to the dorsal and ventral streams

Question 31

Visual agnosia

Answer 31

can see things, but they don’t know what they are
often specific to a particular aspect of visual input and are named accordingly

Question 32

Prosopagnosia

Answer 32

is a visual agnosia for faces that can be acquired either during development (developmental prosopagnosia) or as a result of brain injury(acquired prosopagnosia)

Question 33

fusiform face area

Answer 33

the area of human cortex
parts of it are selectively activated by human faces

and because electrical stimulation of this brain area in humans can metamorphose a viewed face into a completely different face

Question 34

Akinetopsia

Answer 34

deficiency int he ability to see movement progress in a normal smooth fashion

Question 35

MT Area/VS

Answer 35

akinetopsia is often associated with damage to the MT area (middle temporal area) of the cortex
near the junction of the temporal,parietal and occipital lobes