Chapter 3: Sensory systems and Perception: Vision Flashcards
prosopagnosia
inability to recognize faces; usually associated with lesions of the right inferior temporal cortex
sensory adaptation
adjustment of sensory receptors or other elements in a sensory system to different levels of stimulus intensity; allows sensory systems to operate over a wide range of stimulus intensities
acuity
ability of a sensory system to accurately discriminate spatial detail; usually tested by the ability to spatially discriminate two points, as in the Snellen eye chart exam for vision.
Applies to all the sensory systems, but most obviously to vision and somatic sensation
saccade
ballistic eye movement that changes the point of binocular visual fixation; normally occur at a rate of about three to four per second
fovea
area of the human retina specialized for high acuity; contains a high density of cones and few rods.
Most mammals do not have a well-defined fovea, although many have an area of central vision (called the area centralis) in which acuity is higher than in more eccentric retinal regions
primary visual pathway
pathway from the retina via the lateral geniculate nucleus of the thalamus to the primary visual cortex; carries the information that allows conscious visual perception
lateral geniculate nucleus
thalamic nucleus that relays information from the retina to the cerebral cortex
magnocellular system
component of the primary visual processing pathway that is specialized in part for the perception of motion and other aspects of stimulus change; so named because of the relatively large neurons involved
parvocellular system
component of the primary visual processing pathway that is specialized in part for the detection of detail and color; so named because of the relatively small size of the neurons involved
primary visual cortex/ striate cortex/ V1
cortex in the calcarine fissure of the parietal lobe that receives visual input from the thalamus
extrastriate visual cortical area
regions of the visual cortex that lie outside the primary (striate) visual cortex; includes higher-order visual processing areas such as V4, MT, and MST
cortical association areas/ association cortices
regions of cerebral neocortex that are not involved in primary sensory or motor processing
V4
area of extrastriate visual cortex that is probably important in color vision, although it processes other information as well
MT (middle temporal)
in primates, an extrastriate cortical region related to MST that is in part specialized for motion processing
MST (middle superior temporal)
in primates, an extrastriate cortical region related to MT that is in part specialized for motion processing
ventral stream
partially segregated visual processing pathway passing from the primary visual cortex toward the temporal lobe that is especially pertinent to object recognition
dorsal stream
partially segregated visual processing pathway passing from primary visual cortex through extrastriate areas to the higher-order association cortices of the parietal cortex; thought to be concerned primarily with spatial aspects of visual processing
topography
in vision, the study of spatial relationships at different levels of the primary visual pathway
topographical mapping
specification of spatial relationships in the retina and in other stations of the primary visual pathway
cortical magnification
disproportionate representation of cortical space according to peripheral receptor density (such as occurs for the central representation of the fovea of the human eye)
cortical modules/ cortical columns
vertically organized groups of cortical neurons that process the same or similar information; examples are ocular dominance columns and orientation columns in the primary visual cortex
receptive field
region of the receptor surface of a sensory neuron that, when stimulated, elicits a response in the neuron being examined
single-unit recording
method of studying the activity of single neurons using a microelectrode
tuning curve
function obtained when a neuron’s receptive field is tested with stimuli at different orientations; its peak defines the maximum sensitivity of the neuron in question
lightness
in vision, the apparent reflectance of a surface
brightness
technically, the apparent intensity of a source of light; more generally, a sense of the effective overall intensity of a light stimulus
luminance
physical measure of light intensity
simultaneous lightness/brightness contrast
ability of contextual information to alter the perception of a visual target, especially in regard to its luminance (i.e., lightness or brightness; simultaneous brightness contrast) or its color (simultaneous color contrast)
illumination
light that falls on a scene or surface
reflectance
percentage of incident light reflected from a surface (often expressed as the reflectance efficiency function, in which the reflectance of a surface is measured at different wavelengths)
transmittance
percentage of light energy that reaches a detector when passed through a filter
inverse optics problem
impossibility of knowing the world directly by means of light stimuli; arises because of the ambiguity of light patterns projected onto the retina
color
subjective sensations elicited in humans (and presumably many other animals) by different spectral distributions of light
color space
depiction of human color experience in diagrammatic form by a space with three axes representing the perceptual attributes of hue, saturation, and color brightness
trichromat
person or other animal whose color vision depends on three retinal cone types that absorb long, medium, and short wavelengths of light, respectively
dichromat
color-deficient human (and the majority of mammals) whose color vision depends on only two cone types
color contrast
different color appearance of surfaces despite similar spectral returns from them
color constancy
similar color appearance of surfaces, despite different spectral returns from them; usually applied to the similar appearance of objects under different illuminants
cerebral achromatopsia
loss of color vision as a result of damage to the visual cortex
form
perception of object geometry or shape; one of the major visual perceptual qualities
depth
in vision the perception of distance from the observer
monocular
pertaining to one eye
binocular
pertaining to both eyes
monocular depth perception
sense of three-dimensionality when looking at the world with one eye closed
occlusion
blocked view of distant objects by nearer objects
motion parallax
different degree of movement of near and far objects as a function of moving the head or body while observing a scene
stereopsis/ binocular depth perception
special sensation of depth that results from fusion of the two eyes’ views of relatively nearby objects
retinal disparity
geometrical difference between the same points in the images projected on the two retinas, measured in degrees with respect to the fovea
cyclopean fusion
normal sense, when looking at the world with both eyes, that we see it as if with a single eye
binocular rivalry
bi-stable visual experience that occurs when the right and left eyes are presented with incompatible or conflicting images and visual perception alternates between the two images every few seconds
motion
changing position of an object defined by speed and direction within a frame of reference
aperture problem
challenge of determining the speed and direction of a moving line when its ends are obscured by an opening such as a circular hole or a vertical rectangle
apparent motion
sensation of motion elicited by presentation of a stimulus in two successive positions over a brief interval
motion aftereffect
persistence of perceived motion in the opposite direction when a motion stimulus has ceased
fusiform face area
region of the fusiform gyrus that shows enhanced responses to faces relative to other objects
