Chapter 6 Quiz Questions

About ___of the axons of retinal ganglion cells become part of the retina-geniculate-striate pathways

90 percent

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

Akinetopsia

_______________ 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

Blindsight

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

Color

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

G-protein-coupled receptor

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

Photopic; scotopic

__________________ is a visual agnosia for faces

Prosopagnosia

This effect can be observed during the transition from photopic to scotopic vision

Purkinje effect

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

accommodation

Many persons with scotomas

are not consciously aware of their deficits

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

can explain color constancy

Convergence is greatest when inspecting things that are

close

Binocular disparity tends to be greater for _________ objects

closer

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

component

Photopic vision is

cone-mediated

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

constricting the pupils of the eyes

On-center and off-center cells respond best to

contrast

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

fovea

Which of the following cell types are in the human retina?

ganglion cells, bipolar cells, and horizontal cells

In comparison to simple cortical cells, complex cells

have larger receptive fields, do not have receptive fields with static "on" and "off" areas, and are often bilateral

When rhodopsin is exposed to continuous intense light

it loses its red coloring, it loses its ability to absorb light, and it becomes bleached

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

lateral geniculate nuclei

The mechanism of contrast enhancement is

lateral inhibition

When an ommatidium fires, it inhibits its neighbors; this inhibition is called

lateral inhibition

Ciliary muscles adjust the

lens shape

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

monocular; binocular

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

motion

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

near; cylindrical

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

opponent

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

parvocellular; magnocellular

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

parvocellular; magnocellular

The fovea

plays an important role in photopic vision, is an indentation, and contains the highest density of cones

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

prestriate cortex; inferotemporal cortex

Damage to the fusiform face area is often associated with

prosopagnosia

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

receptive field

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

retinex

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

retinotopic

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

retinotopic

Which of the following are involuntary fixational eye movements?

saccades

Persons with a visual agnosia

see objects but can't identify them

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

sharper; depth of focus

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 ______________

straight; circular

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

temporal hemiretina; nasal hemiretina

Most primates are ______________, whereas most other mammals are _______________

trichromats; dichromats

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

where objects are; what objects are