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Pollypocket1220
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The perception of color is what ?
Wavelength
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The perception of brightness is what ?
Amplitude
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Light enters the eye through
The pupil
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The ability to see when light is dim, is what ?
sensitivity
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The ability to see details, increases with pupil constriction, is what ?
Acuity
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The process of adjusting the lens to bring images into focus is what ?
Accomodation
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eyes must turn slightly inward when objects are close is what ?
Convergence
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difference between the images on the two retinas is known as what ?
Binocular disparity
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no receptors where information exits the eye, is known as what ?
blind spot
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high acuity area at center of retina, is known as what ?
Fovea
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photopic (daytime) vision
High-acuity color information in good lighting
this is which type of vision?
cones
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scotopic (nighttime) vision
High-sensitivity, allowing for low-acuity vision in dim light, but lacks detail and color information
what type of vision is this ?
rods
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More ________ in ___ system, increasing sensitivity while decreasing acuity
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Only ____ are found in the fovea
cones
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______ shows the relationship between wavelength and brightness
spectral sensitivity curve
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Shift in relative brightness of colors as we change from photopic to scotopic vision
Is known as what ?
Purkinje effect
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We continually scan the world with small and quick eye movements known as what?
Saccades
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Conversion of one form of energy to another, is known as?
Transduction
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conversion of light to neural signals by visual receptors (photoreceptors), Is known as ?
Visual transduction
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______ describes spectral sensitivity, Is known as?
Absorption spectrum
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The pigment found in rods
Rods are bleached under light and loose their ability to absorb light
Degree of light absorption determines vision
This describes what?
Rhodopsin
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A G protein-linked receptor that responds to light rather than to neurotransmitters, describes what?
Rhodopsin
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Rhodopsin:
In the dark
___channels remain partially open (partial depolarization), releasing _____.?
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Rhodopsin
When light strikes:
___ channels ____
Rods hyperpolarize, inhibiting glutamate release
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what is the primary visual pathway?
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90% of axons of retinal ganglion cells are in this pathway?
Primary visual pathway
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The left _______ of each eye (right visual field) connects to the right ____________ the right hemiretina (left visual field) connects to the left LGN
- hemiretina
- lateral geniculate nucleus (LGN)
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Crossing takes place at the ?
optic chiasm
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Each LGN is divided into 6 layers and receives input only from __________ But since each half of visual field is seen by both eyes, 3 layers get input from one eye and the other 3 layers from the other eye
the contralateral visual field.
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Most LGN neurons that project to primary visual cortex (V1, striate cortex) terminate in the lower part of ________
cortical layer IV
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Retinotopic Organization:
Information received at adjacent portions of the retina remains adjacent in the _____?
striate cortex
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Retinotopic Organization:
More cortex is devoted to areas of high acuity – like the disproportionate representation of sensitive body parts in ______?
somatosensory cortex
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Retinotopic Organization:
About 25% of ______ is dedicated to input from the ____
The _____covers about 2 degrees of visual angle
- primary visual cortex
- fovea
- fovea
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Big cell bodies, bottom two layers of LGN
Particularly responsive to movement
Input primarily from rods
Which layer is this?
Magnocellular layer
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Small cell bodies, top four layers of LGN
Color, detail, and still or slow objects
Input primarily from cones
which layer is this ?
Parvocellular layer
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M & p channels:
Project to slightly different areas in lower layer IV in ______, __ neurons just above the __ neurons.
Project to different parts of visual cortex beyond V1
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nonexistent stripes that the visual system creates for contrast enhancement, Makes edges easier to see
This is what ?
Mach bands
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A cell that receives information _____ the firing of its neighboring cells
inhibits
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The area of the visual field within which it is possible for a visual stimulus to influence (decrease or increase) the firing of a given neuron
Is known as what ?
Receptive Fields of Visual Neurons
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Hubel and Wiesel looked at receptive fields in cat __________, ___, and __________.
- retinal ganglion
- LGN
- lower layer IV of striate cortex
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Receptive fields of ____ areas are smaller than those in the periphery
foveal
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________ receptive fields are circular in shape
Neurons’
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Neurons are _________, each neuron has a receptive field in only one eye
monocular
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Many neurons at each level had receptive fields with ______ and _______ (concentric) areas
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Many cells have receptive fields with a center-surround organization: excitatory and inhibitory regions separated by a _______.
circular boundary
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In the ___________, neurons with circular receptive fields (as in retinal ganglion cells and LGN) are rare
striate cortex
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Most neurons in V1 are either
simple or complex
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receptive fields are rectangular with “on” and “off” regions
is known as?
simple
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also rectangular, larger receptive fields, respond to a particular stimulus anywhere in its receptive field
is known as?
complex
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Receptive Fields in Striate Cortex:
Rectangular
“On” and “off” regions, like cells in layer IV
Orientation and location sensitive
All are monocular
simple
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Receptive Fields in Striate Cortex:
Rectangular
Larger receptive fields
Do not have static “on” and “off” regions
Not location sensitive
Motion sensitive
Many are binocular (depth perception)
complex
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Cells with _____ receptive fields send information on to cells with more _____receptive fields
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Functional vertical columns exist such that all cells in a column have the same _______ and ______.
- receptive field
- ocular dominance
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Proposed by Young, refined by Helmholtz
Three types of receptors, each with a different spectral sensitivity
Which type of theory ?
Component theory
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Component theory
We do have 3 types of cones
_cones - short wavelength, about 430 nm
_ cones - medium wavelength, about 530 nm
_ cones - long wavelength, about 560 nm
Similar to RGB system
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Proposed by Hering
Two different classes of cells encoding color, and another class encoding brightness
Each encodes two complementary color perceptions
Accounts for color afterimages and colors that cannot appear together (reddish green or bluish yellow). Also for colorblindness.
This describes which theory ?
Color: opponent processing theory
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coding of color by cones seems to operate on a purely ______ basis, ______processing of color is seen at all subsequent levels
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Dual _______color cells respond to wavelength contrast
opponent
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color is determined by the proportion of light of different wavelengths that a surface reflects
This is known as which type of theory ?
Retinex theory
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Flow of visual information:
_____ to
_____ relay neurons, to
1˚ visual cortex (_____), to
2˚ visual cortex (_____), to
Visual association cortex
- Retina
- Thalamic
- striate
- prestriate
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Areas of blindness in contralateral visual field due to damage to primary visual cortex
Detected by perimetry test
This is known as?
Scotomas
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Patients may be unaware of scotoma – missing details supplied by “______”
completion
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pathway from primary visual cortex to dorsal prestriate cortex to posterior parietal cortex
The “where” pathway (location and movement), or
Pathway for control of behavior (e.g. reaching)
This describes which stream?
Dorsal stream
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pathway from primary visual cortex to ventral prestriate cortex to inferotemporal cortex
The “what” pathway (color and shape), or
Pathway for conscious perception of objects
This describes which stream?
Ventral stream
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Damage to where pathway - ________: deficit in visually guided reaching
optic ataxia
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Damage to “what” pathway - _______: unable to identify object by sight
visual agnosia
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Inability to distinguish among faces
Often associated with damage to the ventral stream
This is known as ?
Prosopagnosia
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