Chapter 6 Vision Flashcards
Astigmatism
a decreased responsiveness to one kind of line or another, caused by an asymmetric curvature of the eyes
Binocular input
stimulation from both eyes
Bipolar cell
type of neuron in the retina that receives input directly from the receptors
Blind spot
area at the back of the retina where the optic nerve exits; it is devoid of receptors
Blindsight
the ability to respond in limited ways to visual information without perceiving it consciously
Colour Constancy
the ability to recognize colors despite changes in lighting
Colour vision deficiency
inability to perceive color differences
Complex cell
type of visual cortex cell located in areas V1 and V2 that responds to a pattern of light in a particular orientation anywhere within its large receptive field
Cones
type of retinal receptor that contributes to color perception
Dorsal stream
visual path in the parietal cortex that helps the motor system locate objects; the “where” path
End-stopped (hypercomplex) cell
type of visual cortex cell that resembles complex cells; responds best to stimuli of a precisely limited type, anywhere in a large receptive field, with a strong inhibitory field at one end of its field
Feature detectors
neurons whose responses indicate the presence of a particular feature
Fovea
a tiny area of the retina specialized for acute, detailed vision
Ganglion cell
type of neuron in the retina that receives input from the bipolar cells
Horizontal cell
type of cell that receives input from receptors and delivers inhibitory input to bipolar cells
Inferior temporal cortex
portion of the cortex where neurons are highly sensitive to complex aspects of the shape of visual stimuli within very large receptive fields
Koniocellular neurons
small ganglion cells that occur throughout the retina
some of these are colour sensitive and have various responses to stimuli.
Lateral geniculate nucleus
thalamic nucleus that receives incoming visual information
Lateral inhibition
the reduction of activity in one neuron by activity in neighboring neuron
Law of specific nerve energies
statement that whatever excites a particular nerve always sends the same kind of information to the brain
Magnocellular neurons
large cell bodies with large receptive fields that are distributed evenly throughout the retina
specialized for depth, movement and overall patterns.
Middle temporal cortex (MT or V5)
area of the brain that detects moving objects
Midget ganglion cell
ganglion cells in the fovea of humans and other primates
Motion blindness
an impaired ability to perceive movement
Negative Colour after imaging
result of staring at a colored object for a prolonged length of time and then looking at a white surface, the image is seen as a negative image, with a replacement of red with green, green with red, yellow and blue with each other, and black and white with each other
Opponent-process theory
idea that we perceive color in terms of opposites.
visual system neurons beyond the receptors themselves respond with an increase in activity to indicate one colour of light and a decrease to indicate the opposite colour.
The three pairs of opposites are red-green, yellow-blue, and white black.
Optic Nerve
ganglion cell axons that exit through the back of the eye and continue to the brain
Parvocellular Neurons
small cell bodies with small receptive fields in or near the fovea
specialized for perception of colour and fine details.
Photopigments
chemicals contained in rods and cones that release energy when struck by light
Primary Visual Cortex
area of the cortex responsible for the first stage of visual processing
Prospagnosia
the inability to recognize faces due to damage of several brain areas
Pupil
an opening in the center of the iris where light enters
Receptive field
the area in visual space that excites or inhibits any neuron
retina
the rear surface of the eye, which is lined with visual receptors
retinal disparity
the discrepancy between what the left and right eyes see
Retinex Theory
concept that the cortex compares information from various parts of the retina to determine the brightness and color for each area
Rods
type of retinal receptor that detects brightness of light
saccades
Saccades
voluntary eye movements
Secondary visual Cortex v2
area of the brain that processes information from the primary visual cortex and transmits it to additional areas
Sensitive period
time early in development when experiences have a particularly strong and enduring influence
Simple cell
type of visual cortex cell that has a receptive field with fixed excitatory and inhibitory zones
Strabismus (or strabismic amblyopia or lazy eye)
a condition in which the eyes do not point in the same direction
Superior colliculus
swelling on either side of the tectum; important to visual processing
Trichromatic theory (Young-Helmholtz Theory)
Trichromatic theory (Young-Helmholtz theory) theory that color is perceived through the relative rates of response by three kinds of cones, each one maximally sensitive to a different set of wavelengths
Ventral stream
visual paths in the temporal cortex that are specialized for identifying and recognizing objects; the “what” path