Chapter 6

Question 1

When the pupils are constricted, the image falling on each retina is ___________ and there is a greater ____________.

Answer 1

sharper; depth of focus

Question 2

The process of adjusting the configuration of the lenses to bring images into focus on the retina is called:

Answer 2

accommodation.

Question 3

When we direct our gaze at something ___________, the lens tends to assume its natural _____________ shape.

Answer 3

near; cylindrical

Question 4

Convergence is greatest when inspecting things that are:

Answer 4

close

Question 5

Binocular disparity tends to be greater for _________ objects.

Answer 5

closer

Question 6

_____ and _____ cells play a role in lateral communication within the human retina.

Answer 6

Amacrine; horizontal

Question 7

______________ vision predominates in good lighting and provides high-acuity colored perceptions of the world. In contrast, the more sensitive ______________ vision predominates in low lighting.

Answer 7

Photopic; scotopic

Question 8

The ______ effect can be observed during the transition from photopic to scotopic vision.

Answer 8

Purkinje

Question 9

_____ are a type of involuntary fixational eye movements.

Answer 9

Saccades

Question 10

Rhodopsin is a(n) ____________________ that responds to light rather than to neurotransmitter molecules.

Answer 10

G-protein–coupled receptor

Question 11

About ___ percent of the axons of retinal ganglion cells become part of the retina-geniculate-striate pathways.

Answer 11

90

Question 12

All signals from the right visual field reach the left primary visual cortex, either ipsilaterally from the _______________ of the left eye or contralaterally from the ____________ of the right eye.

Answer 12

temporal hemiretina; nasal hemiretina

Question 13

Although the _________ constitutes only a small part of the retina, a relatively large proportion of the primary visual cortex is dedicated to the analysis of its output.

Answer 13

fovea

Question 14

The retina-geniculate-striate system is _____________. This means two stimuli presented to adjacent areas of the retina will excite adjacent neurons at all levels of the system.

Answer 14

retinotopic

Question 15

_______________ neurons are particularly responsive to color, fine pattern details, and stationary or slowly moving objects; in contrast, ________________ neurons are particularly responsive to movement.

Answer 15

parvocellular; magnocellular

Question 16

The perception of edges ultimately boils down to the perception of:

Answer 16

contrast

Question 17

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

Answer 17

receptive field

Question 18

On-center and off-center cells respond BEST to:

Answer 18

contrast

Question 19

The main difference between simple cortical cells and lower layer IV neurons is that the borders between the “on” and “off” regions of the receptive fields of simple cortical cells are ____________ rather than ______________.

Answer 19

straight; circular

Question 20

Unlike simple cortical cells, which are all _______________, many complex cortical cells are _____________.

Answer 20

monocular; binocular

Question 21

According to the ____________ theory, there are three different kinds of color receptors, each with a different spectral sensitivity.

Answer 21

component

Question 22

According to the ____________ theory, if an increase in the response of a particular visual neuron signals green, a decrease signals red.

Answer 22

opponent

Question 23

Most primates are ______________, whereas most other mammals are _______________.

Answer 23

trichromats; dichromats

Question 24

_________________ constancy refers to the fact that the perceived color of an object is not solely a function of the wavelengths reflected by it.

Answer 24

Color

Question 25

According to the ___________ theory of color vision, the color of an object is determined by its reflectance.

Answer 25

retinex

Question 26

_______________ refers to the ability of certain patients to respond to visual stimuli in their scotomas even though they have no conscious awareness of the stimuli.

Answer 26

Blindsight

Question 27

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

Answer 27

prestriate; inferotemporal

Question 28

According to one theory, the dorsal stream is involved in the perception of __________________ and the ventral stream is involved in the perception of ___________________.

Answer 28

where objects are; what objects are

Question 29

__________________ is a visual agnosia for faces.

Answer 29

Prosopagnosia

Question 30

_________________ is a deficiency in the ability to see movements progress in a normal, smooth fashion.

Answer 30

Akinetopsia

Question 31

What type of physical energy is transduced into electrochemical signals by specialized sensory neurons in each of our five primary sensory systems?

Answer 31

Vision: photons
Audition: sound waves
Somatosensation: pressure, vibration, heat/ cold
Taste/ Smell:chemicals

Question 32

What does each type of photoreceptor cell respond to, and how are the different types distributed in the retina?

Answer 32

Rods: low-light vision ( no detail or color)
Many rods → a few bipolar cells → ganglion cells
Cones: high light vision (detail and color)
Each cone → bipolar cells → ganglion cells

Question 33

What happens when the photoreceptor cells (rods, cones) are exposed to light?

Answer 33

Rods and cones hyperpolarize, no longer stimulate bipolar cells

Question 34

What are the 3 major layers of neurons that make up the retina, and what is the direction of communication to the brain? (i.e., how does light ultimately become an action potential?)

Answer 34

back front
Photoreceptor → Bipolar cells → Ganglion cells

First photoreceptors transduce light sends signals too bipolar cells, then they send signals to ganglion cells

Question 35

What is the most common cause of color-blindness?

Answer 35

Due to genetics, the most common type of color blindness is red-green (8%)

Question 36

Explain how visual information from right and left eyes compared to the right and left visual fields gets into the brain.

Answer 36

Everything from the left visual field goes to the right hemisphere even if it’s picked up by the right eye and vise versa

Question 37

Describe the “major” and “minor” pathways of visual information processing from retinal ganglion cells to the brain.

Answer 37

Major: Retina → LGN → Primary visual cortex (occipital lobe) → secondary visual pathway –> assoc. (ventral/ dorsal)

Minor: Retina → Superior colliculus (midbrain tectum) → Post parietal lobe

Question 38

Explain at least one mechanism by which our brains process visual information to sharpen our perception of edges (e.g., enhance our ability to visually distinguish objects from background).

Answer 38

Lateral inhibition: retinal and LGN: neurons firing maximally to the bright side of a given edge inhibit the firing of adjacent neurons- sharpening our edge perception

Center- surround firing: vision neurons [retina (some r. Ganglion cells), LGN, primary visual cortex] are excited or inhibited depending on where in their receptive field light hits: in an “on-center” or “off-center” manner fire most strongly to contrast edges

Question 39

What types of simple stimuli do individual primary visual cortex (V1) neurons respond to?

Answer 39

Simple cells: simple lines

• Input from only one eye
• Rectangular receptive fields with “on/off” areas
• Fire maximally to straight edge of particular orientations

Complex Cells: lines but also movement

• Particular orientation and movement direction
• Input from either eye or both (binocularity → depth perception)

Question 40

Explain the change in visual perception that may be caused by single-hemisphere vs. dual-hemisphere damage to primary visual cortex (V1), and explain why people with extensive, dual-hemisphere V1 damage may still show some visual guided behavior, albeit “unconsciously.”

Answer 40

One hemisphere: one visual field will be damaged
Both hemispheres: cortical blindness (total or partial blindness), may experience a blind spot due to intact superior colliculus.
Some messages might be still sent down the dorsal stream (where/ how) but they are unaware of it

Question 41

Describe the specific types of disturbances of visual perception that are associated with damage to secondary visual cortex areas V4 and V5, compared to inferior temporal lobe (inferotemporal cortex) and posterior parietal lobe. What are the various visual agnosias called, specifically?

Answer 41

V4 Damage: loss of normal color vision “achromatopsia”
V5 Damage: motion blindness “akinetopsia”
Agnosias: Ventral Stream damage
Object agnosia: inability o recognize previously familiar objects
Prosopagnosia: inability to recognize faces

Question 42

In situations where the level of illumination is high and sensitivity is not important, the visual system responds by:

Answer 42

constricting the pupils of the eyes.

Question 43

Ciliary muscles adjust the:

Answer 43

lens shape.

Question 44

Photopic vision is:

Answer 44

cone-mediated.

Question 45

Visual signals from the left nasal hemiretina are projected directly to the:

Answer 45

lateral geniculate nuclei.

Question 46

An interior designer explains that turquoise is an underappreciated color because it is calming during the day but brightens a dim room in the evening. The _____ effect helps explain this perception.

Answer 46

Purkinje

Question 47

The transduction of light by rods reflects a(n) _____ in the release of the neurotransmitter _____.

Answer 47

decrease; glutamate

Question 48

Because of the way that it is organized, the visual system is referred to as:

Answer 48

retinotopic

Question 49

At least two parallel channels of communication flow through each lateral geniculate nucleus. One runs through the ______________ layers and a second runs through the _____________ layers.

Answer 49

parvocellular; magnocellular

Question 50

The mechanism of contrast enhancement is:

Answer 50

lateral inhibition.

Question 51

In comparison to simple cortical cells, complex cortical cells:

Answer 51

are more numerous.

Question 52

The major advantage of the retinex theory over the classic component and opponent process theories of color vision is that the retinex theory:

Answer 52

can explain color constancy.

Question 53

Many persons with scotomas:

Answer 53

are not consciously aware of their deficits.

Question 54

Damage to the fusiform face area is often associated with:

Answer 54

prosopagnosia.

Question 55

Persons with a visual agnosia:

Answer 55

see objects but can’t identify them.

Question 56

The middle temporal (MT) area of human cortex appears to play an important role in the perception of:

Answer 56

motion