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an anatomically distinguishable set of neurons
Visual cortical "area"
How cells look in the Visual cortical "area"
similar histological characteristics; cells must look the same
Visual cortical "area" pattern of afferent and efferent connections (connections to input from the retina)
What test shoes that neurons have the same response to a stimulus so they appear to have the same function in the Visual cortical "area" ?
functional MRI (fMRI)
How does the Visual cortical "area" respond to visual stimuli?
In the Visual cortical "area" there is a representaton of____ of the visual field
The Visual cortical "area" comprises one (or more) complete _____ ______ of the visual world
Optical imaging of cortex in monkey. Data is polotted in a color coded map that shows
activitiy related to orientation of the stimuli
A neuron may act differently when it is grouped with
Some techniques for Extrastriate vision research
- 1. recordings of single neuron activity (cats)
- 2. Anatomical staining and labeling teq (animal) with CO
- 3. Optical imaging (animal)
- 4. lesion studies (human and animal)
when staining with CO to determine which cells of the cortex are active. Which ones appear white and which dark
- active cells = white
- inactive cells = dark
Optical imaging monitors a group or single neuron?
groups of neurons
How does optical imaging measure activity?
Detects changes in cortical reflectance due to variations in bld flow (active area = incr bld flow)
What type of techniques/study for extrastriate vision research lets you observe how a lesion affects vision or function in body?
What are some modern techniques/study for extrastriate vision research?
- 1. Positron emission tomography (PET)
- 2. Functional magnetic resonance imaging (MRI)
Which modern techniques/study for extrastriate vision research measures changes in bld oxygenation due to neurala activity?
Which modern techniques/study for extrastriate vision research measures changes in bld flow related to neural activity?
PET (position emission tomography)
What does the pt do during a fMRI?
pt is assigned tasks or looks at stimuli
Where can the primary visual cortex be seen?
Can;t be seen laterally, has to be seen if you cut corpus callosum in half and look at medial part of brain, BUT you can view with a fMRI w/o cutting brain open
Neurons in VI have relatively SMALL receptive fields and respond to ___ features of objects in the VF
Name some examples of local features that neurons in V1 respond to
- orientation, length, width, speed and direction of motion of bars and edges (spacial freq)
- wavelength of light
Neurons in extra-striate visual areas (V2-V5,...) have much LARGER receptive fields and respond to ___ properties of objects in the VF
Name some examples of local features that neurons in V2-V5 respond to
color rather than just wavelength, specific shapes and objects irrespective of orientation, forma dn motion coherence.
Extrastriate cortical cell properties, graph showing percentage of cells in each of first 5 cortical areas selective for orientation, direction, color and binocular disparity. Why are some of the % more than 100%??
Each cell may respond to more than one characteristic. (ex. cell can respond to both color and orientation).
Proportions vary from area to area (look at table)
Which area is mostly for color vision>
V4 (but also has some stereo, direction and orientation)
Which area is mostly for direction?
Which layer is VI (striate cortex) most and least pronounced with CO staining?
- Most= IIIB (koniocellular)
- Least= IVCa (Magnocel)
Staining with CO where are the "blobs" in VI?
centered above ocular dominance colums
What happens when you stain the V2 area with CO?
Stripes perpendicular to V1/V2 border.
What are the "Thick stripes" when you stain the V2 area with CO?
- M pathway
- (imput from V1 layer to IVCa/ OUtput to V3 and V5 (MT))
What are the "Thin stripes" when you stain the V2 area with CO?
- Parvo-blob pathway
- Input from V1 CO blobs/ output to V4, V3 and V5
What are the "Pale stripes" when you stain the V2 area with CO?
- Parvo-Interblob pathway (interstripes)
- input from V1 layers 2&3 outside of CO blobs; output to V4
What are the 3 complete retinotopic maps in V2 (Brodman's Area 18)?
- 1. Thick Dark CO stripes
- 2. Thin DArk CO stripes
- 3. Pale CO stripes
What does the Thick Dark CO stripes represent in V2?
M pathway: motion, orientation, binocular disparity
What does the Thin Dark CO stripes represent in V2?
P-Blob pathway: wavelength/color
What does the Pale/Interstirpes CO stripes represent in V2?
P-Interblob pathway: orientation, binocular disparity
In V2 what is there a high proportion of?
disparity-tuned neurons (they like depth)
Many neurons in V2 will respond to?
What is an example of "Illusory Contours"?
What type of input does area V3 recieve?
Magno and parvo (integration!)
What are the two parts of V3?
- 1. VP: ventral posterior area
- 2. Dorsal V3 (V3 proper)
What does the VP and also Dorsal V3 represent?
- Upper visual field
- Lower visual field
Where does V3 output go to?
Mostly to V5 and posterior parietal cortex, also some to V4
Where does V3 contribute to?
integration of magno & parvo streams
What area was believe to be part of V3, but neurons are much less selective to direction and speed of motion and projects to both temporal and parietal lobes?
Where does V4 get its major input from and what is it info is it mainly related to?
Parvo pathway (blob & interblob); perception of color and form, some neurons specific for simple shapes and forms
What does damage of V4 called?
What is achromotopsia often associated with and why?
prosopagnosia; due to proximity to V4 to IC in fusiform gyrus
What is the fusiform gyrus for?
What is prosopagnosia?
can't remember and recognize faces
What is the major input of V5(MT) from and what info is it mainly related to?
magno pathway and perception of motion
What are the size are the reeptive fields and what are they called?
Large receptive fields, parasols
What is V5 specific for?
PERCEPTION of motion, direction and velocity, orientation and depth
What are two examples of illusory motion?
- 1. Barber Pole Illusion: lines look like they are moving in a certain direction when they aren't
- 2. Motion After-effects
Damage to V5 results in?
What is akinetopsia?
What happens in the 'ventral' cortical stream?
- 1. global pattern processing
- 2. object and pattern recognition (what?)
- 3. Face recognition (who?)
What are the two "streams" of higher-order visual info processing?
- 1. ventral cortical stream
- 2. dorsal cortical stream
What happens in the 'dorsal' cortical stream?
- 1. Global motion processing
- 2. Processing location in 3D space (where?)
- 3. provides info for visually guided actions (how?)
The "ventral" what stream is largely from what input, and what is the function?
- Parvo and koniocellular input
- recognition of shapes, objects, faces, color perception
Damage to ventral stream can case what?
achromatopsia, drawing/object agnosia, prosopagnosia
The "dorsal" where stream is largely from what input, and what is the function?
- magnocellular (but not entirely)
- VI>V2>V3&V5>LIP &7A> frontal eye fields
- LIP: lateral intraparietal area
Damage to dorsal stream can cause?
- Akinetopsia (can't estimate speed of moving object)
- Deficits in visually guided behavior
What is it called when we see only a small portion of our VF to which we are attending; AKA rest of our visual field is suppressed