Chapter 6 Vision

Question 1

Bipolar cells

Answer 1

Neurons that receive messages from visual receptors

Located closer to the center of the eye

Send messages to ganglion cells

Question 2

Amacrine cells

Answer 2

Control the ability of the ganglion cells to respond to shapes, movements, or other specific aspects of visual stimuli

Question 3

Macula

Answer 3

The center of the human retina

Question 4

Fovea

Answer 4

Allows for acute and detailed vision

Packed tight with receptors

Nearly free of ganglion axons and blood vessels

Question 5

Midget ganglion cell

Answer 5

A single bipolar cell and a single ganglion cell with an attached receptor in the fovea

Question 6

The vertebrate retina consists of two kind of receptors?

Answer 6

Rods

Cones

Question 7

Rods

Answer 7

Most abundant in the periphery of the eye and respond to faint light

Good during green+ yellow light because is easier to detect in the dark

120 million per retina

Question 8

Cones

Answer 8

Most abundant in and around the fovea

Essential for color vision and more useful in bright light

6 million per retina

Question 9

Photopigments

Answer 9

Chemicals contained by both rods and cones that release energy when struck by light

Question 10

The perception of color is dependent upon?

Answer 10

The wavelength if the light

Shortest: 400 nm violet

Longest: 700 no ( red)

Question 11

Colors have three things?

Answer 11

Hue

Intensity

Value

There is a lot of overlap between colors

Question 12

Discrimination among colors depend upon?

Answer 12

The combination of responses by different neurons

Question 13

Two major interpretations of color visions include?

Answer 13

Trichromatic theory/ Young-Helmholtz

Opponent process theory

Question 14

Trichromatic theory

Answer 14

Color perception occurs through the relative rates of response by three kinds of cones

Short, medium, long wavelength

Each cone is maximally sensitive to a different set of wavelengths

Question 15

Opponent process theory

Answer 15

We perceive color in terms of paired opposites

A mechanism that perceives color on a continuum from red to green and another from yellow to blue

Question 16

Horizontal cells

Answer 16

Cells in the eye that make inhibitory contact onto bipolar cells

Question 17

Lateral geniculate nucleus

Answer 17

Part of the thalamus specialized for visual perception

Destination for most ganglion cell axons

Sends axons to other parts of the thalamus and to the visual areas of the occipital cortex

Cortex and thalamus feed information back and forth to each other

Question 18

Lateral inhibition

Answer 18

The reduction of activity in one neuron by activity in neighboring neurons

The retinas way responsible of sharpening contrasts to emphasize the borders of objects

Question 19

Receptive field

Answer 19

Refers to the part of the visual field that either excites or inhibits a cell in the visual system of the brain

The point in space from which light strikes it

Question 20

Ganglion cells of primates generally fall into three categories?

Answer 20

Parvocellular neurons

Magnocellular neurons

Konicellular neurons

Question 21

Parvocellular neurons

Answer 21

Highly sensitive to detect color and visual detail/ details of shape

Have smaller cell bodies and small receptive fields

Located in or near the fovea

Connect only to the lateral geniculate nucleus

Question 22

Magnocellular neurons

Answer 22

Highly sensitive to large overall pattern and movement

Throughout the retina

Larger cell bodies and visual fields

Connect to the lateral geniculate nucleus and visual areas of the thalamus

Question 23

Konicellular neurons

Answer 23

Small cell bodies

Found throughout the retina

Connect to the lateral geniculate nucleus, parts of the thalamus, and the superior colliculus

Question 24

Primary visual cortex (area V1)

Answer 24

Receives information from the lateral geniculate nucleus and is the area responsible for the first stage of visual processing

Question 25

Blindsight

Answer 25

An ability to respond to visual stimuli that they report not seeing

Question 26

Ventral stream

Answer 26

The most magnocellular visual paths in the temporal cortex Specialized for identifying and recognizing objects

Question 27

Dorsal stream

Answer 27

Helps the motor system to find objects and move towards them The visual path in the parietal cortex

Question 28

Complex cells

Answer 28

Responds to pattern of light in a particular orientation and most strongly to a stimulus perpendicular to its access Large receptive fields that can not be mapped into fixed excitatory or inhibitory zones Located v1 or v2

Question 29

End stopped or hyper complex cells

Answer 29

Respond to a bar shaped pattern of light anywhere in its large receptive field, provided the bar does not extend beyond a certain point

Question 30

Feature detectors

Answer 30

Neurons whose response indicate the presence of a particular feature/ stimuli

Question 31

Inferior temporal cortex

Answer 31

Contains cells that respond selectively to complex shapes but are insensitive to distinctions that are critical to other cells

Question 32

Visual agnosia

Answer 32

The inability to recognize objects despite satisfactory vision Caused by damage to the pattern pathway usually in the temporal cortex

Question 33

Prosopagnosia

Answer 33

Inability to recognize faces Occurs after damage to the fusiform gyrus

Question 34

Saccades

Answer 34

A decrease in the activity of the visual cortex during quick eye movements Preventing confusion and blurring of images

Question 35

Strabismus

Answer 35

A condition in which the eyes do not point in the same direction Lazy eye

Question 36

Astigmatism

Answer 36

A blurring of vision for lines in one direction caused by an asymmetric curvature of the eyes