Test 2 (Chapter 6) Flashcards
nanometers
billionths of a meter; light is between 380 and 760
infrared waves
wavelengths that are too long for humans to see but rattlesnakes can see them
wavelength
a property of light that plays in important role in the perception of color
intensity
a property of light that plays an important role in the perception of brightness
brightness
intensity of light
sensitivity
in vision, the ability to detect the presence of dimly lit objects
acuity
the ability to see the details of objects
retina
the amount of light that reaches this part of the eye is regulated by the irises
pupil
light enters the eye through this part of the eye which is a hole in the lens
iris
the donut-shaped bands of contractile tissue that gives our eyes their characteristic color
ciliary muscles
the eye muscles that control the shape of the lenses
accomodation
the process of adjusting the configuration of the lenses to bring images into focus on the retina
converge
turn slightly inward
binocular disparity
the difference in the position of the retinal image of the same object on the two retinas
receptors
cells that are specialized to receive chemical, mechanical, or radiant signals from the environment; also proteins that contain binding sites for particular neurotransmitters
horizontal cells
type of retinal neurons whose specialized function is lateral communication
bipolar cells
bipolar neurons that form the middle layer of the retina
amacrine cells
a type of retinal neurons whose specialized function is lateral communication
blind spot
the area on the retina where the bundle of axons on the retinal ganglion cells penetrate the receptor layer and leave the eye as the optic nerve
fovea
the central indentation of the retina, which is specialized for high-acuity vision
completion
the visual system’s automatic use of information obtained from receptors around the blind spot, or scotoma, to create a perception of the missing portion of the retinal image
surface interpolation
the process by which the visual system perceives large surfaces, by extracting information about edges and from it, inferring the appearance of adjacent surfaces
cones
the usual receptors in the retina that mediate high acuity color vision in good lighting
rods
the visual receptors in the retina that mediate achromatic, low-acuity vision under dim light
duplexity theory
the theory that cones and rods mediate photopic and scotopic vision, respectively
photopic vision
cone-mediated vision, which predominates when lighting is good
scotopic vision
rod-mediated vision, which predominates in dim light
nasal hemiretina
the half of each retina next to the nose
temporal hemiretina
the half of each retina next to the temple
spectral sensitivity curve
a graph of the relative brightness of light in the same intensity presented at different wavelengths
photopic spectral sensitivity curve
the graph of the sensitivity of cone-mediated vision to different wavelengths of light
scotopic spectral sensitivity curve
the graph of the sensitivity of rod-mediated vision to different wavelengths of light
Purkinje Effect
in intense light, red and yellow wavelengths look brighter than blue or green wavelengths of equal intesity, in dim light, blue and green wavelengths look brighter than red and yellow wavelengths of equal intensity
fixational eye movements
involuntary movements of the eyes (tremor, drifts, and saccades) that occur when a person tries to fix his or her gaze on (i.e., stare at) a point
saccades
the rapid movements of the eyes between fixations
transduction
the conversion of one of energy to another
pigment
any substance that absorbs light
rhodopsin
the photopigment of rods
bleaching
loss of its color
absorption spectrum
a graph of the ability of a substance to absorb light of different wavelengths
retina-geniculate-striate pathways
the major visual pathway from each retina to the striate cortex (primary visual cortex) via the lateral geniculate nuclei of the thalamus
primary visual cortex
the area of the cortex that receives direct input from the lateral geniculate nuclei
lateral geniculate nuclei
the six-layered thalamic structures that receive inout from the retinas and transmit their output to the primary visual cortex
retinotopic
organized, like the primary visual cortex, according to a map of the retina
parvocellular layers
the layers of the lateral geniculate nuclei that are composed of neurons with small cell bodies; the top four layers (also called the p layers)
magnocellular layers
the layers of the lateral geniculate nuclei that are composed of neurons with large cell bodies; the bottom two layers (also called m layers)
mach bands
the nonexistent stripes of brightness and darkness running adjacent to the edges; they enhance the contrast at each edge and make the edge easier to see
contrast enhancement
the intensification of the perception of edges
lateral inhibition
inhibition of adjacent neurons or receptors in a topographic array
receptive field
the area of the visual field within which it is possible for the appropriate stimulus to influence the firing of a visual neuron
monocular
involving only one eye
on-center cells
visual neurons that respond to lights share in the center of their receptive fields with “on” firing and to lights shone in the periphery of their field with “off” firing
off-center cells
visual neurons that respond to lights shone in the center of their receptive fields with “off” firing and to lights shone in the periphery of their fields with “on” firing
simple cells
neurons in the visual cortex that respond maximally to straight edge stimuli in a certain position and orientation
complex cells
neurons in the visual cortex that respond optimally to straight edge stimuli in a certain orientation in any part of their receptive field
binocular
involving both eyes
ocular dominance
responding more robustly to stimulation of one eye than they do to the same simulation of the other
retinal disparity
when a preferred stimulus is presented to both eyes at the same time but in slightly different positions on the two retinas
component theory
the theory that the relative amount of activity produced in three different classes of cones by light determines its perceived color (aka trichromatic theory)
opponent-process theory
the theory that a visual receptor of a neuron signals one color when it responds in one way (e.g., by increasing its firing rate) and signals the complementary color when it responds in the opposite way (e.g., by decreasing its firing rate)
complementary colors
pairs of colors (e.g., green light and red light) that produce white or gray when combined in equal measure
trichromats
possessing three color vision photopigments
color constancy
the tendency of an object to appear the same color even when the wavelengths of light that it reflects change
retinex theory
Land’s theory that the color of an object is determined by its reflectance, which the visual ability of adjacent surfaces to reflect short, medium, and long wavelengths
dual-opponent color cells
neurons that respond to the differences in the wavelengths of light stimulating adjacent areas of their receptive field
cytochrome oxidase
an enzyme present in particularly high concentrations in the mitochondria of dual-opponent color cells of the visual cortex
blobs
peglike, cytochrome oxidase-rich, dual opponent color columns
secondary visual cortex
areas of cerebral cortex that receive most of their input from primary visual cortex
visual association cortex
areas of cerebral cortex that receive input from areas of secondary visual cortex as well as from secondary cortex other sensory systems
prestriate cortex
the band of tissue in the occipital lobe that surrounds the primary visual cortex and contains areas of secondary visual cortex
inferotemporal cortex
the cortex of the inferior temporal lobe, in which is located an area of secondary visual cortex that is involved in object recognition
posterior parietal cortex
an area of association cortex that receives input from the visual, auditory, and somatosensory systems and is involved in the perception of spatial location and guidance of voluntary behavior
scotoma
an area of blindness produced by damage to, or disruption of, an area of the visual system
perimetry test
the procedure used to map scotomas
hemianopsic
having a scotoma that covers half of the visual field
conscious awareness
the ability to perceive one’s experiences; typically inferred from the ability to verbally describe them
blindsight
the abilit of some patients who are blind as a consequence of cortical damage to unconsciously see some aspects of their visual environments
dorsal stream
the group of visual pathways that flows from the primary visual cortex to the dorsal prestriate cortex to the posterior parietal cortex; according to one theory, its function is the control of visually guided behavior
ventral stream
the group of visual pathways that flows from the primary visual cortex to the ventral prestriate cortex to the inferotemportal cortex; according to one theory, its function is conscious visual perception
“where” vs. “what” theory
the theory that the dorsal stream mediated the perception of where things are and the ventral stream mediates the perception of what things are
“control of behavior” vs. “conscious perception” theory
the theory that the dorsal stream mediates behavioral interactions with objects and the ventral stream mediates conscious perception of objects
prosopagnosia
visual agnosia of faces
agnosia
an inability to consciously recognize sensory stimuli of a particular class that is not attributable to a sensory deficit or to verbal or intellectual impairment
visual agnosia
a failure to recognize visual stimuli that is not attributable to sensory, verbal, or intellectual impairment
movement agnosia
difficulties in recognizing movement
object agnosia
difficulties in recognizing objects
color agnosia
difficulties in recognizing color
fusiform face area
an area of human cortex, located at the boundary between the occipital and temporal lobes, that is selectively activated by human faces
akinetopsia
a deficiency in the ability to perceive motion, which often results from damage to the dorsal visual pathway
