Block 12 Flashcards
Inability to recognize faces
Prosopagnosia
- dorsal processing
- parietal path
- where path
They scribe the visual path that processes what
Process motion
Optic ataxia may result from damage in which cortical processing stream
Dorsal-dorsal
Inability to point or reach for a target
Optic ataxia
Form of attention that alerts you when another vehicle swerves into your lane
Bottom up
Form of attention from an external source
Bottom up
Observer controls what they are attending to
Top down
Clinical condition that may be caused by abnormal connections between cortical modules
Synaesthesia
Damage to inferotemporal cortex may result in deficits in analyzing what
Form
Akinetopsia may result from damage to
Area v5
As the number of distractions increases, the ability to detect the salient objects
Remains the same
Shifts in attention alter the responses of cells located where
Area v4
Type of attention: looking for a friend in a crowd of people
Top down
Type of attention: responding to the slamming of the door
Bottom up
Type of attention: searching for quarters in a drawer of loose change
Top down
Prosopagnosia is most likely to be accompanied by
Achromatopsia
Cortical areas that are a part of the ventral processing system
IT and V4
Inability to perceive 2 objects simultaneously
Simultagnosia
Visual hallucinations experienced in Charles bonnet syndrome have been compared to
Phantom limb syndrome
- Demonstrated in elderly people
- used to treat amblyopia
Perceptual learning
How many areas of the brain are distinct visual areas
20
Each visual area has what
A retinotopic map
Are the processing streams independent of each other
No
Which stream is critical for identifying and recognizing objects
Temporal, ventral, what stream
Which stream plays a role in motion perception, localization in visual space, and action organization
Dorsal, parietal, where stream
2 parts of the dorsal stream
Dorsal-dorsal stream
Ventral-dorsal stream
Which arm of the dorsal stream processes action info
Dorsal-dorsal stream
Damage to the dorsal-dorsal stream may result in
Optic ataxia
Inability to point to or reach for a visual target
Optic ataxia
Which arm of the dorsal stream includes extrastriate area MT/V5
Ventral-dorsal
Which arm of the dorsal stream plays a role in space perception and action organization
Ventral-dorsal
The parvo path has strong input to
Ventral stream
Mango path inputs mainly to which stream
Dorsal stream
Which retinogeniculate pathways may provide input to
Both corical processing streams
Area that has an abundance of cells with chromatic sensitivities
V4
Cells in which area respond to complex forms, including faces
IT
This area is well adapted to color perception
V4
The area plays a role in form perception
IT
V4 and IT are part of which stream
Ventral
Areas MT/V5 are a part of which stream
Dorsal
Which imaging technique has better resolution: fMRI or PET
fMRI
Which imaging technique uses a radioactive tracer to observe changes in blood flow indicating increased cortical metabolism
PET
Which imaging technique reveals cortical activity by detecting levels of oxygenation (BOLD- blood oxygen level dependent)
fMRI
If asked to view a certain color, but stream may have elevated activity
Ventral
If asked to focus on the shape or form of an object, which stream becomes active
Ventral
If asked to focus on the movement of on object, which stream will have increased activity
Dorsal
Motion and position are processed along
Dorsal
Color and form info are processed along
Ventral
Integration of the info from dorsal and ventral with memory is coordinated by
Prefrontal cortex
Area been though to play a role in cognition
Prefrontal cortex
Cells in the MT/V5 are capable of analyzing
Motion info
The movement of a plaid pattern (an integrated stimulus of 2 components) appears as a
Single object moving in an intermediate direction by area MT/V5
What area has also been studied with random dot kinematograms
MT/V5
MT/V5 is more active when viewing what kind of object
Moving object
A motion illusion that occurs in the absence of motion
MAE (motion aftereffect)
Motion detectors mediating the MAE are located
In the cortex
Where it’s he first site of substantial interaction between the2 eyes
Cortex
Size of receptive fields of cells in IT
Large
Cells in IT respond best to
Sophisticated shapes
Which cells respond best to bars, edges and gratings
Cells in the striate cortex
Area of the brain that responds well to objects, but not scrambled objects or object fragments
LOC (lateral occipital complex)
What area of the brain responds well to faces, but not other objects
FFA (fusiform face area)
Which area of the brain is strongly activated by objects and places, but not faces
PPA (parahippocampal place area)
What cortical area processes:
1- face
2- color
And are in close proximity
1- FFA
2-V4
Pts who suffer from prosopagnosia may also manifest what (because of location of brain areas)
Cerebral achromatopsia
This form of attention is volitional
Top down
Directing our attention on each object of interest to see what is available is an example of
Serial processing
What type of processing facilitates detection of the salient feature
Preattentive processing
Phenomenon in which we cannot readily see the difference between 2 images
Change blindness
What condition can make changes between 2 images more visible
- presented in rapid sequence (triggers our exogenous attention)
What condition can make changes between 2 images less visible
2 images presented simultaneously (dont as readily elicit our attention)
Which area of the brain is involved in topdown visual attention
Prefrontal cortex
Do cells in the striate cortex demonstrate topdown attention
No
Lesions in the striate cortex produce
Simple blind spots (scotomas)
Extrastriate lesions can lead to
Visual agnosia
Defect in the perception of motion
Akinetopsia
Where is the damage in akinetopsia
Dorsal processing stream
Lesions to the superior temporal lobe can lead to
Visual neglect (only recognize one side - only eat one half of plate, only shave one side of face, etc)
Not able to percieved more than one object at a time
Simultagnosia
Simultagnosia may be seen in pts with what syndrome
Balint’s syndrome
Condition where there is bilateral damage to parietal lobes
Balint’s syndrome
The presentation of a letter or number results in the perception of a color
A form of synesthesia
Is it uncommon for patients with visual loss to experience visual hallucination (phantom vision)
No, it is common
Complex visual hallucinations that often take the form of a person, but are recognized as the patient as not being real, occur in what syndrome
Charles bonnet syndrome
Area of the brain that plays a big role in encoding memories
Hippocampus
Is there evidence that neurons with highly specialized receptive fields may play a role in encoding memories
Yes
Perceptual learning has been used to improve what 2 things
- visual function in amblyopia
- near VA in children with low vision
The cortex manifests a significant degree of what
Specialization
Brain areas involved in ventral processing stream
V4 and IT
Brain areas involved in dorsal stream
MT/V5
What part of the brain may coordinate integration of info from the 2 systems
Prefrontal cortex
Neurons in what part of the brain correspond closely with our perceptions and playa role in perceptual learning, striate cortex or higher visual centers?
Higher visual centers
What picture can be used to possibly train vision
Necker cube
Stimulus for: EOG
Adaptation
Stimulus for: ffERG(flash)
Ganzfield flash
Stimulus for: ffERG(flicker)
Ganzfield flash
Stimulus for: pERG
Pattern reversal
Stimulus for: mfERG
Multifocal flash pattern
Stimulus for: VEP
Pattern reversal
Stimulus for: mfVEP
Multifocal pattern reversal
Magnitude of: EOG
6 mV
Magnitude of: ffERG (flash)
1 mV
Magnitude of: ffERG (flicker)
1 mV
Magnitude of: pERG
5 microV
Magnitude of: mfERG
1 microV
Magnitude of: VEP
5 microV
Magnitude of: mfVEP
1 microV
Tissue evaluated with: EOG
RPE
Tissue evaluated with: ffERG (flash)
- PR
- Bipolar/Mueller
- GC
Tissue evaluated with: ffERG (flicker)
Cone
Tissue evaluated with: pERG
GC
Tissue evaluated with: mfERG
Macular function
Tissue evaluated with: VEP
Visual cortex
Tissue evaluated with: mfVEP
Focal visual cortex
Components of: EOG
Arden ratio
Components of: ffERG (flash)
- a wave
- b wave
- oscillatory pot
Components of: ffERG (flicker)
Amplitude - phase
Components of: pERG
Amplitude and phase
Components of: mfERG
Focal macular function
Components of: VEP
P-100 Amp/Lat
Components of: mfVEP
Focal cortical function
Do you signal average: EOG
No
Do you signal average: ffERG(flash)
No
Do you signal average: ffERG (flicker)
No
Do you signal average: pERG
Yes
Do you signal average: mfERG
Yes
Do you signal average: VEP
Yes
Do you signal average: mfVEP
Yes
With EOG, is there a lower dipole voltage under dark or light adapted conditions
Dark adapted
One condition in which the ERG is normal, but the EOG is abnormal is
Best’s autosomal Dominant Vitteliform Maculopathy (fired egg appearance)
The a wave of the ERG is from what cells
PR
The b wave of the ERG is from what cells
Bipolar layer and the depolarization of the mueller cells
The oscillatory potentials of the ERG is from what cells
Ringing in neural transmission at amacrine layer
The c wave of the ERG is from what cells
RPE
Are ffERG’s useful for maculopathies
No bc only a small part of the retinal is affected
Stimulus used in scotopic ERG
Dim blue stimulus to limit response to rods only
What flicker is used in the photopic ERG
30 Hz
What does a 60 Hz ERG look like
Flat because you have reach the CFF
Which looks best at problems like retinitis pigmentosa that affect entire classes of cells
ff-ERG
Is ffERG good for focal lesions, such as maculopathy
No
Which 2 tests use a steady state alternating phase checkerboard or grating stimulus
VEP and pERG
Do you signal average pERG and VEP
Yes, due to the low voltage outputs
Area of most organized primary visual reception in cortex
Visual cortex area 17
Measures macular/foveal function
VEP
VEP: If there is a decrease in amplitude and a delayed response in an eye, suspect
Amblyopia
VEP: If there is an extreme delay in response, suspect
MS
Which test will require best, precise fixation
Mf-ERG
Do you signal average mf-ERG
Yes
Presents local luminance shifts (flashes)
Mf-ERG
Long term chloroquine toxicity can cause what
Central vision loss -> bulls eye maculopathy
What cells give rise to most of large positive going potential seen in b wave of ff-ERG(flash)
Mueller cells
30 yo pt with 20/20OD and 20/80OS has normal ffERG, mild amplitude reduction and a latentncy delay in high spatial frequency VEP, occurring only on OS. Suspect?
Amblyopia
Pt is on hydroxychloroquine; 65 yo and has been on it many years. Which study proved most useful to VFs and OCT in diagnosis of this pt?
Mf-ERG
Frequency characterized by nearly extinguished ffERG
Retinitis pigmentosa
35 you with longstanding VA loss bilaterally getting worse. Just noticeable granular pigment in macula. No issue with night vision. Vague family Hx of going blind at young age. Suspect cone dystrophy. What tests would provide useful info supporting diagnosis: ffERG(flicker), dark adapted ffERG, pERG
All
- ffERG(flicker): bc it uses cones
- dark adapted ffERG: to see if it is only cones or if rods are involved
- pERG: primary cones bc looking at retinal response to acuity
A subject view two patches of light. 1 patch consists of an additive mixture of 475 and 510nm and the other was a mixture of 490 and 520nm. By adjusting the intensities of each of the wavelengths that constitute these patches, the subject is ale to perfectly match the 2 patches. The subject’s vision:
Could be either monochromatic, dichromatic, or trichromatic
What cone photopigment evolved most recently
Chlorolabe
3 perceptual dimensions of color
Hue
Brightness
Saturation
Does a person with monochromatic have color discrimination?
No, they only have 1 cone photopigment
What is the only way to differentiate color is pt is monochromatic
If the quantal absorption’s are different
In a dichromatic patient, if they are unable to match two patches of different wavelengths of light, does the pt possess the ability to make discriminations based purely on wavelength?
Yes
- if they can match them, they do not have the ability to make wavelength based discrimination
2 stimuli that appear identical, it are physically different
Metamers
Most humans have what kind of vision
Trichromatic
What part of the cone photopigment is identical for all
Chromophore
What part of the cone photopigment is the visually inert chain of amino acids
Opsin
the M and L cone opsin genes are found on what chromosome
X
Where is the s cone photopigment gene located
Chromosome 7
Where is the rhodopsin gene found
Chromosome 3
Are M and L cone opsin genes similar or different
Very similar
- 98% homologous
A stimulus of 540 nm has a hue of
Green
A stimulus of 570 nm has a hue of
Yellow
3 wavelengths that do not change hue as their intensity is increased
Blue-478
Green-503
Yellow-578
Stimuli with wavelengths shorter than 503 appear
Blue as intensity increases
Stimuli longer than 503 appear
Yellow as intensity is increased
Appears as a pastel
Desaturated color
Does a monochromatic stimulus of 570nm appear more or less saturated than a monochromatic stimulus of any other wavelength
Less saturated
Which wavelengths have the best discrimination
495 and 590nm
The approximately constant color appearance of objects as lighting conditions change
Color constancy
What is processed by bipolar hue channels
Color
What are the 2 bipolar hue channels
Red-green
Blue-yellow
In the red-green or blue-yellow channel, are colors signaled individually or simultaneously
Individually
What is coded by a white-black channel
Brightness
A wavelength below 570 causes
Inhibition
A wavelength above 570 causes
Excitation
Spectral sensitivity function for a typical non color opponent neuron peaks at
555nm
Postreceptoral antagonism first occurs where
Bipolar cells
Color vision is normally
Trichromatic
What plays a critical role in coding color info
Opponent processing
What type of neurons are in the LGN
Color opponent
L and M cones _______ eachother
Oppose
__ cones are opposed by an addition of L and M
S cones
Non color opponent cells sum the input of
L and M
Wiring diagrams give the connections of what cells
Cones, horizontal cells and bipolar cells
For foveal red-green cells, what contributes to the excitatory center
A single L cone
For foveal red-green cells, what contributes to the inhibitory surround
Many m cones
For blue-yellow cells, what contributes to the excitatory center
S cones
For blue-yellow cells, what contributes to the inhibitory surround
L and M cones
An achromatic cell has what input to both the excitatory center and inhibitory surround
L and M to both
- makes cell monochromatic
Cells that manifest red-green opponency
Parvo
Cells that manifest yellow-blue opponency
Konio
Cells that are non-color opponent
Magno
Most distal color opponent neurons
Bipolar
Hue info is encoded by
Color opponent neurons
Allows us to precisely specify any possible color
CIE color system
The quantity of each primary required for a match is referred to as what
Tristimulus value
For wavelengths from 450 to 525, what is required to obtain a match
Negative amounts of lamdaR are required
With the CIE diagram, how do you find coordinate Z
1- (X + Y)
So: X + Y + Z = 1
How to find excitation purity
A/(A+B)
A: from W to the line
B: from line to end of diagram
A mixture of 3 parts 580 and 1 part 490; which side of the diagram will it intersect closer to
Closer to 580 (3/4 of the way there)
- connect line from white to edge of diagram to find the dominant wavelength of the mixture
- then use a and b to find excitation purity
Complementary colors when mixed together produce
White
How to find a complement wavelength from the CIE diagram
Go from the given wavelength through W to opp side of diagram
Specifies the relative amounts of primaries necessary to match a color sample
CIE diagram
Do CIE primaries physically exist
No, they are imaginary
Why does the CIE primaries use imaginary primaries
To avoid use of negative quantities
What percent of the population manifest anomalous color vision
4.5
Are most color vision anomalies inherited or acquired
Inherited
Which kind of color vision anomalies are non progressive and pose no threat
Inherited
What kind of color vision anomalies are secondary to disease or drug toxicity
Acquired
Missing 1 of the 3 cone photopigment
Dichromacy
When chlorolabe is missing
Deuteranopia
When erythrolabe is missing
Protanopoia
When cyanolabe is missing
Tritanopia
In deuteranopia, what is chlorolabe replaced with
Erythrolabe
In protanopia, what is erythrolabe is replaced by what
Chlorolabe
3 photopigments are present but absorption spectrum of 1 is displaced
Anomalous trichromacy
Chlorolabe is displaced toward longer wavelengths
Deuteranomalous trichormacy
Erythrolabe spectrium is displaced toward shorter wavelengths
Protanomalous trichromacy
People with protan and deutan usually confuse what colors
Reds and greens
People with Tritan vision confuse what colors
Blues and yellows
4 characteristics that distinguish anomalous color vision
Spectral sensitivity
Wavelength discrimination
Color confusion lines
Perception of saturation
The luminance V(lamda) function normally peaks at about
555nm
Protanopic V(lamda) curve shows what
BIG displacement toward shorter wavelengths
Deuteronopic v(lamda) function shows what
SLIGHT displacement toward longer
The greater dislocation of the protanopic luminance function suggest that which cones play a greater role in generating the normal v(lamda)function
L cones
Protanopoia have difficulty seeing what color
Red
Luminosity functions in anomalous trichromacy
Same general dislocation as dichromatic functions, but less pronounced
Protanopia and deuteranopia have well developed wavelength discrimination at what wavelength
490nm
There is no ability for people with protanopia and deuteranopia to discriminate at what wavelengths
545 and beyond
In pts with deuteranopia and protanopia, the only way they can discriminate among longer than 545 nm is by
Difference in luminance
All colors falling along confusion line are
Indistinguishable
Are all spectral stimuli equally saturated
No
In normal trichromacy, what wavelength appears less saturated (more whitish)
570
Deuteranopia function intersects the abscissa at (neural point)
498nm
Protanopic function intersects the abscissa at (neutral point)
492 nm
The neutral point in tritanopia is
569nm
Do people with normal color vision and anomalous trichromacy manifest neutral points
No
Wavelength discrimination is best in the region of
The neutral point
The most commonly inherited anomaly is
Anomalous trichromacy
The boy always receives the defective CV gene from which parent
Mother
Hereditary or acquired: symmetric
Hereditary
Hereditary or acquired: stable
Hereditary
Hereditary or acquired: no cause
Hereditary
Hereditary or acquired: asymmetric
Acquired
Hereditary or acquired: recent history of color naming errors
Acquired
Hereditary or acquired: unstable
Acquired
Hereditary or acquired: caused by disease or toxicity
Acquired
Changes in transmission propertiesof lens secondary to aging result in what color vision anomaly
- this is known as what rule
- blue yellow anomalies
- Kollner’s rule
Outer retinal disease result in what CV anomalies
Blue yellow
Disease of the inner retina, ON, visual paths and visual cortex result in
Red green anomalies
Rare conditions where the pt manifests monochromatic vision
Achromatopsias
What color lenses minimize the bleaching of rhodopsin and may be recommended for pts with achromatopsias
Dark red lenses
Distortion of color
Chromatopsias
Digitalis and fluorescein may produce
Xanthopsia (yellow vision)
Most commonly used CV tests
Pseudoisochromatic plate tests
Do pseudoisochromatic plate tests distinguish dichromatic and anomalous trichormatic
No
Appearance of 546 stimulus in angel anomaloscope
Bright
Appearance of 670 stimulus in angel anomaloscope
Dim
