Chapter 6

Question 1

This increases the ability of the lens to refract (bend) light
and thus brings close objects into sharp focus. When we
focus on a distant object, the lens is flattened. The process
of adjusting the configuration of the lenses to bring
images into focus on the retina is called ______

Answer 1

accommodation

Question 2

When we direct our
gaze at something near, the tension on the ligaments
holding each lens in place is
adjusted by the _____ muscles , and the lens assumes
its natural cylindrical shape.

Answer 2

ciliary muscles

Question 3

But the positions of the images
on your two retinas can never correspond
exactly because your two eyes do not view the world
from exactly the same position. _____ _____
the difference in the position of the same image on the
two retinas is greater for close objects than for distant
objects; therefore, your visual system can use the degree
of binocular disparity to construct one three-dimensional perception from two two-dimensional retinal
images

Answer 3

Binocular disparity

Question 4

The retina
is composed of five layers of
different types of neurons: receptors, horizontal cells,
bipolar cells, ____ cells and _____ ____ cellls

Answer 4

amacrine cells, and retinal ganglion cells.

Question 5

The other is that for the bundle of retinal
ganglion cell axons to leave the eye, there must be a gap in
the receptor layer; this gap is called the ___ ____

Answer 5

blind spot.

Question 6

The ______ is 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)

Answer 6

fovea

Question 7

or example, the color and
brightness of large unpatterned surfaces are not perceived directly but are filled
in (completed) by a completion process called ____ ______ (the process by
which we perceive surfaces; the visual system extracts information about edges and from it
infers the appearance of large surfaces).

Answer 7

surface interpolation

Question 8

From this observation emerged the _____ theory
of vision the theory that cones and rods mediate different kinds of vision. _____ vision (cone-mediated
vision) predominates in good lighting
and provides high-acuity (finely detailed) colored perceptions of the world.
In dim illumination, there is not enough
light to reliably excite the cones, and the
more sensitive _____ vision (rod-mediated vision) predominates.

Answer 8

duplexity Photopic scotopic

Question 9

By far the most important thing to remember about
spectral sensitivity curves is that humans and other animals with both cones and rods have two of them: a
_____ spectral sensitivity curve and a _____ spectral sensitivity curve.

Answer 9

photopic, scotopic

Question 10

n 1825,
Jan Purkinje described the following
occurrence, which has become known
as the ______ effect (pronounced
pur-KIN-jee ). One evening, just before dusk, while Purkinje was walking
in his garden, he noticed how bright
most of his yellow and red flowers appeared in relation to his blue ones

Answer 10

Purkinje

Question 11

These involuntary fixational eye movements are of three kinds: tremor, drifts, and ______
(small jerky movements, or flicks; pronounced sahKAHDS ).

Answer 11

saccades

Question 12

_____ is the conversion of one form of energy to
another. Visual ______ is the conversion of light to
neural signals by the visual receptors.

Answer 12

Transduction

Question 13

When the pigment which became

known as _____ was exposed to continuous intense light, it was bleached (lost its color),

Answer 13

rhodopsin

Question 14

Many  pathways  in  the  brain  carry
visual information. By far the largest
and  most  thoroughly  studied  visual
pathways  are  the  \_\_\_-\_\_\_\_ pathways, which conduct signals from each retina to the primary
visual  cortex, or  striate  cortex, via
the  lateral  geniculate  nuclei of the
thalamus.

Answer 14

retina-geniculatestriate

Question 15

The retina-geniculate-striate system is ______;
each level of the system is organized like a map of the
retina.

Answer 15

retinotopic

Question 16

One channel runs through
the top four layers. These layers are
called the _____ layers (or P
layers) because they are composed
of neurons with small cell bodies
(parvo means small ). The other channel runs through the
bottom two layers, which are called the ______ layers (or M layers) because they are composed of neurons with
large cell bodies ( magno means large ).

Answer 16

parvocellular

magnocellular

Question 17

The second is that when a receptor fires, it inhibits its neighbors via the lateral neural network; this inhibition is called _____ inhibition because it spreads
laterally across the array of receptors.

Answer 17

lateral

Question 18

All the neurons were _______; that is, each neuron

had a receptive field in one eye but not the other.

Answer 18

monocular

Question 19

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 19

receptive field

Question 20

On-center cells 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.

Answer 20

Off-center cells display the opposite pattern: They
respond with inhibition and off firing in response to
lights in the center of their receptive fields and with on
firing to lights in the periphery of their receptive fields.

Question 21

_____ cells, like lower layer IV neurons, have
receptive fields that can be divided into antagonistic on and off regions and are thus unresponsive to diffuse light. And like lower layer IV
neurons, they are all monocular. The main difference is that the borders between the on and
off regions of the cortical receptive fields of
simple cells are straight lines rather than circles

Answer 21

Simple

Question 22

_____ cells are more numerous than simple cells. Like
simple cells, ______ cells have rectangular receptive
fields, respond best to straight-line stimuli in a specific
orientation, and are unresponsive to diffuse light. However, complex cells differ from simple cells in three important ways. First, they have larger receptive fields.
Second, it is not possible to divide the receptive fields of
complex cells into static on and off regions: A complex cell responds to a particular straight-edge stimulus of
a particular orientation regardless of its position within
the receptive field of that cell.

Answer 22

Complex

Question 23

The _____ ______ (trichromatic theory) of color
vision was proposed by Thomas Young in 1802 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 to be encoded by
the ratio of activity in the three kinds of receptors.

Answer 23

component theory

Question 24

Another theory of color vision, the ____-_____
theory of color vision, was proposed by Ewald Hering in
1878. He suggested that there are two different classes of
cells in the visual system for encoding color and another
class for encoding brightness.

Answer 24

opponent-process

Question 25

________ colors are

pairs of colors (e.g., green light and red light) that produce white or gray when combined in equal measure.

Answer 25

Complementary

Question 26

____ ______ refers to

the fact that the perceived color of an object is not a simple function of the wavelengths reflected by it.

Answer 26

Color constancy

Question 27

According to Land s ______ theory of color vision,
the color of an object is determined by its reflectance
the proportion of light of different wavelengths that a
surface reflects.

Answer 27

retinex

Question 28

And they are. For example,
____-_____ color cells in the monkey visual cortex respond with vigorous on firing when the center of their
circular receptive field is illuminated with one wavelength,
such as green, and the surround (periphery) is simultaneously illuminated with another wavelength, such as red.

Answer 28

dual-opponent

Question 29

Many neurons in these peglike columns are particularly rich in the mitochondrial
enzyme ____ ______; thus, their distribution in
the primary visual cortex can be visualized if one stains
slices of tissue with stains that have an affinity for this
enzyme.

Answer 29

cytochrome oxidase

Question 30

To the relief of instructors and students alike, the term ____ has become
the accepted scientific label for peglike, cytochrome
oxidase rich, dual-opponent color columns.

Answer 30

blobs

Question 31

Primary visual cortex, as you have learned, is that area
of cortex that receives most of its input from the visual
relay nuclei of the thalamus (i.e., from the lateral geniculate
nuclei). Areas of secondary visual cortex are those that

Answer 31

receive most of their input from the primary visual cortex,
and areas of visual association cortex are those that receive
input from areas of secondary visual cortex as well as from
the secondary areas of other sensory systems.

Question 32

The primary visual cortex is located in the posterior
region of the occipital lobes, much of it hidden from view
in the longitudinal fissure. Most areas of secondary visual
cortex are located in two general regions: in the prestriate
cortex and in the inferotemporal cortex. The prestriate
cortex is the band of tissue in the occipital lobe that surrounds the primary visual cortex. The _________
cortex is the cortex of the inferior temporal lobe. 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.

Answer 32

inferotemporal

Question 33

Damage to an area of the primary visual cortex produces a
______ an area of blindness in the corresponding
area of the contralateral visual field of both eyes

Answer 33

scotoma

Question 34

For example, patients who are ______ (having a scotoma covering
half of the visual field) may see an entire face when they
focus on a person s nose, even when the side of the face in
the scotoma has been covered by a blank card.

Answer 34

hemianopsic

Question 35

______ is the ability of such patients to respond to visual stimuli in their scotomas even though they
have no conscious awareness of the stimuli

Answer 35

Blindsight

Question 36

The _____ stream flows from the
primary visual cortex to the dorsal prestriate cortex to the
posterior parietal cortex, and
the ventral stream flows from
the primary visual cortex to the
_____ prestriate cortex to the
inferotemporal cortex see Figure 6.28 on page 158.

Answer 36

dorsal , ventral

Question 37

_______, briefly put, is visual agnosia for faces. Let

me explain.

Answer 37

Prosopagnosia

Question 38

_____ is a failure of recognition (gnosis

means to know ) that is not attributable to a sensory deficit or to verbal or intellectual impairment

Answer 38

Agnosia

Question 39

______ is a deficiency in the ability to see movement

progress in a normal smooth fashion.

Answer 39

Akinetopsia