Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
98 Cards in this Set
- Front
- Back
What 3 cells make up the vertical pathway?
|
Photoreceptors, bipolar cells and ganglion cells
|
|
What do Bipolar cells mainly do?
|
They used for convergence and divergence of information
|
|
What are the 3 types of bipolar cells and what do each of them do?
|
Diffuse bipolar cells - for sensitivity
Midget Bipolar cells - for acuity On and off-bipolar cells - for changes in illumination |
|
What are ganglion cells for??
|
On and Off center receptive fields
|
|
what is an eye disease that affects the scotoma?
|
Retinitis pigmentosa
|
|
Defintion of contrast
|
The difference in illumination between a figure and its background
|
|
Definition of acuity
|
The smallest spatial detail that can be resolved
|
|
How do vision scientists measure visual acuity?
|
They use the smallest visual angle of a cycle of grating
|
|
How do eye doctors measure visual acuity?
|
They use distance, say 20/20
|
|
Herman Snellen invented...
|
A method for designation visual acuity
He had the "stroke" equal ro 1/5 of the letter size |
|
Spatial Frequency
|
The number of cycles of a grating per unit of visual angle - usually in degrees
|
|
Cycles per degree
|
The number of dark and bright bars per degree of visual angle
|
|
What are the 3 basics rules of sine gratings
|
They are...
- Patterns of stripes with fuzzy boundaries are quite common - The edge of any object produces a single stripe, often blurred by a shadow, in the retinal image - The visual system appears to break down images into vast number of components, each is a sine wave grating with particular spatial frequency |
|
What pattern of retinal ganglion cells elicits the strongest response?
|
Medium Frequency
|
|
What is the order of the Visual pathway? Involving the Superior Colliculus
|
Goes to the Pulvinar nucleus, and then to the secondary visual cortex and then to higher order visual cortical areas
|
|
What is the order of the visual pathway? Involving the LGN
|
The lateral Geniculate nucleus goes to the primary visual cortex. From here it goes to the second visual cortex, and then to higher order visual cortical areas
|
|
What signals are send to EITHER the superior colliculus or the lateral geniculate nucleus
2 Cells |
Contralateral Nasal Retional Ganglion cell Axons, and Ipsilateral Temporal Retinal cell Ganglion cell axons
|
|
What is the LGN?
|
Lateral Geniculate Nucleus
The axons of retinal ganglion cells synapse in the LGN |
|
What are two cell types that are in the LGN?
|
Parvocellular (small) and Magnocellular (large)
|
|
Where does the parvocullular neurons receive their input?
|
From midget Cells
|
|
What is another name for striate cortex?
|
Primary visual cortex or V1
|
|
How many cells are in the striate cortex?
|
200 million!
|
|
What are two important features of striate cortex??
|
Topographical mapping - which is cortical topography, and
the dramatic scaling of information from different parts of visual field This is cortical magnification |
|
Visual acuity declines in an orderly fashion with...
|
Eccentricity
|
|
Selective Responsiveness
Orientation tuning |
The tendency of neurons in striate cortex to respond optimally to certain orientations and less to others
|
|
Many cortical cells respond espeically well to these 4...
|
Bars, edges, gratings, direction
|
|
Each LGN cell responds to one eye or the other, but
BUT.. second point |
Never to both
But, each striate cortex cell can respond to input from both eyes Ocular Dominance Columns |
|
End stopping
|
The process by which cells in the cortex first increase their firing rate as the bar lenght increases to fill up its receptive field, and then decreases their firing rate as the bar is lenghtened further
|
|
Adaptation
|
A reduction in responce caused by prior or continuing stimulation
|
|
What 3 theories did Oliver Selfridge come up with?
|
- Simple model of letter recognition
- Perception by committee - The Pandemonium Model of Letter recognition |
|
Good continuation
|
Group elements to form smootly continuing lines
|
|
Common Fate
|
Group elements moving in the same direction together
|
|
Synchrony
|
Group elements changing at the same time together
|
|
Common Region
|
Elements perceived to be part of a large region are grouped together
|
|
Connectedness
|
Elements that are connected to each other are grouped together
|
|
What are the Gestalt figure-ground assignment principles
4 |
Surroundedness, size, symmetry, parallelism
|
|
Object recognition starts _______ figure-ground assignment ______
|
Object recognition starts before figure-ground assignment finishes
|
|
Where/how system
|
Object localization manipulation - Parietal Cortex
Dorsal Stream |
|
What system
|
Object identification
IT cortex Ventral Stream |
|
What is the range of visible light?
|
400 nm to 700 nm
|
|
problem of univariance
|
A set of different wavelenght-intensity combinations can elicit exactly the same response from a single type of photoreceptor
|
|
Scotopic
|
Dim light levels at or below the level of bright moonlight
Rods are sensitive to scotopic light levels |
|
What is photopigment in rods?
|
Rhodopsin
|
|
ALl rods have same sensitivity to wavelenght, making______
|
it impossible to discriminate light
|
|
What are the 3 varieties of cone photoreceptors?
|
S-cones (short wavelenghts)
M-Cones (middle) L-cones (long) |
|
Trichromatic Theory of color processing
|
The color of any light is defined in our visual system by the relationships between a set of three numbers, the outputs of three receptor types now known to be the three cones
This is the first level of processing |
|
Hue
|
Chromatic aspect of a color
|
|
Saturation
|
Chromatic strenght of a hue
|
|
Brightness
|
Distance from black in color space
|
|
Lateral Geniculate nucleus has cells that are
|
maximally stimulated by spots of light
|
|
Some cells in the LGN are...
|
excited by L-cone onset in center and inhibited by M-cone onsets in their curround
|
|
Opponet color theory
|
The perception of color is based on the output of three mechanisns
|
|
what are the three color opponency in the opponent color theory
|
Red-Green
Blue-Yellow Black-White |
|
Negative Afterimage, and what does it show us?
|
A visual image seen after the stimulus has been removed
This is a way to see opponent colors in action |
|
What are the 2 binocular cues?
|
Convergnce and retinal disparity
|
|
7 monocular cues
|
Light and Shadow
Occlusion Motion parallax Relative Size and Familiar Size Relative Clarity Texture gradient Linear perspective |
|
Diffuse Bipolar Cells
|
Detecting low light sensitivity
|
|
midget bipolar cells
|
At the fovea
Cones in a one to one relationship Cones -> Midget bipolar cells -> Retinal Ganglion cells |
|
Temporal information is...
|
ipsalateral
|
|
Nasal informaton travels
|
Contralaterally
|
|
Superior Colluculus responds to
|
movement
|
|
Lateral Geniculate Nucleus is responsible for
|
Perceptual experience
|
|
Motion Parallax
|
closer objects seem to be moving faster than distant objects
|
|
Linear perspective
|
Linear lines appear to converge as they approach the horizon
|
|
Visual acuity
|
The distance at which a person can just identity the letters divided bythe distance at which a person with normal vision can just identify the letters
|
|
20/20 vision explained
|
If you have to be 20 feet to discern detail that someone at 20 feet can discern, you have 20/40 vision
|
|
- Visual acuity is much poorer in the periphery than the
|
Fovea
|
|
- Spatial frequency
|
The number of cycles of a grating per unit of visual angel
|
|
- Retinal ganglion cells are “tuned” to
|
Spatial frequency
|
|
Retinal Ganglion cells each respond best
|
to a specific spatial frequency that matches its receptive-field size
|
|
- Lateral Geniculate nucleus
|
a structure in the thalamus, part of the midbrain, that receives input from the retinal ganglion cells and has input and output connections to the visual cortex
|
|
- Magnocellular layers
|
the neurons in the bottom two layers of the lateral geniculate nuclea, which are physically larger than those in the top four layers. Receives input from M ganglion cells
|
|
- Parvocellular layer
|
The neurons in the top 4 layers of the LGN which are physically smaller than those in the bottom 2 layers. Receives input from P ganglion cells
|
|
- In the LGN 1,4,6 layers receives info _______
and 2,3,5 ________ |
- In the LGN 1,4,6 layers receives info conralateral, and 2,3,5 receive ipsilateral
|
|
- V1, Striate cortex, primary visual cortex
|
receives direct inputs from the lateral geniculate nucleus as well as feedback from other brain areas and is responsible for processing visual information
|
|
- Cortical magnification
|
the amount of cortical area devoted to a specific regin in the visual field
|
|
Neurons in Striate cortex are
|
elongated and respond to stripes
|
|
o Oreintation tuning
|
the tendency of neurons in striate cortex to respond optimally to certain orientations and less to others
|
|
o Ocular dominance
|
the property of the receptive fields of striate cortex neurons by which they demonstate a preference responding somewhat more rapidly when a stimulus is presented in one eye than when it is presented in the other
|
|
o Simple cells
|
clearly defined excitatory and inhibitory regions – phase sensitive
|
|
o Complex cells
|
a neuron whose receptive field characteristics cannot be easily predicted my mapping with spots of light
|
|
o Hypercolumn
|
a 1-millimeter block of striate cortex containing two sets of columns, each covering every possible orientation which one set preferring input from the left eye and one set preferring input from the right eye
|
|
- Middle (midlevel) vision
|
a loosely defined stage of visual processing that comes after basic features have been extracted from the image and before object recognition and scene understanding
|
|
- Illusory contour
|
a contour that is perceived even though nothing changes from one side of the contour to the other in the image – the arrow
|
|
- Good continuation
|
two elements will tend to group together if they seem to lie on the same contour
|
|
- Similarity
|
the tendency of 2 features to group together will increase as the similarity of them increases
|
|
- Common region
|
two features will tend to group together if they appear to be part of the same large region
|
|
- Necker cube
|
an outline that is perceptually bi-stable. Unlike the situation with most stimuli, two interpretations continually battle for perceptual dominance
|
|
o Relateability
|
the degree to which two line segments appear to be part of the same contour
|
|
- Recognition by components
|
object recognition model which holds that objects are recognized the identities and relationships of their component parts
|
|
- Prosopagnosia
|
an inability to recognize faces
|
|
- Agnosia
|
a failure to recognize objects in spite of the ability to see them
|
|
- Phototropic
|
light intensities that are bright enough to stimulate the cone receptors and bright enough to saturate the rod receptors
|
|
- S – cone
|
short wavelengths – 440 nm peak
|
|
- M-cone –
|
middle wavelengths – 535nm peak
|
|
- L-cone
|
long wavelenght peaks 565
|
|
- Metamers
|
different mixtures of wavelengths that look identical. More generally, any pair of stimuli that are perceived as identical in spite of physical differences
|
|
Saturation, which color is most, which is least?
|
white has 0, red is fully saturated
|