Chapter 4: Visual Cortex + Beyond Flashcards
Define Cortical Magnification
While the fovea only covers 0.01% of the retina, signals from fovea account for 8-10% of the cortical map’s area
Explain Position Emission Tomography (PET) scans
Brain activity is monitored via blood flow via radioactivity caused by an injected radioactive tracer
Explain Functional Magnetic Resonance Imagaing (fMRI)
Brain activity is monitored via magnetic response of hemoglobin
( Brain activity takes up oxygen, making hemoglobin more magnetic)
What is the Subtraction Technique?
(test condition) - (initial condition) = (activity due to stimulation)
What are the 4 types of columns in the visual cortex?
- Location columns
- Orientation columns: adjacent columns change orientation preference in order (90 degrees, 85 degrees, 80 degrees, etc.)
- Ocular dominance columns: columns alternate between L and R eyes at 0.25-0.5mm apart)
- Eye preference has degrees (1=L, 4=equal, 7=R) - Hypercolumns (ice-cube model): contains a location column, L-R dominance columns, and a complete set of orientation columns (0-180 degrees)
Define Lesioning
Destruction or removal of tissue in the nervous system
According to U+M, what are the pathways in the visual cortex that transmit info regarding what is seen and where it is located?
What pathway: ventral pathway (lower) aka temporal lobe
Where pathway: dorsal pathway (upper) aka parietal lobe
What tasks did U+M use during their research to prove the what and where pathways in the visual cortex?
Object discrimination: researchers had monkeys identify a target object when given 2 options
(task was difficult once the temporal lobe was partially removed)
Landmark discrimination: researchers had monkeys remove the food cover closest to a cylinder
(task was difficult once the parietal lobe was partially removed)
Where are the ventral and dorsal pathways located?
The pathways originate in the retina, and continue through 2 types of ganglion cells to the cortex
According to G+M, what is the dorsal pathway responsible for?
- Location
2. Action (how)
What evidence supports G+M’s proposal of the dorsal pathway being responsible for 2 types of info?
Patient D.F.: isolated damage to ventral pathway and exhibited agnosia (could not name familiar objects)
- She couldn’t draw objects in front of her but could draw from memory
- She couldn’t copy orientation but could put mail through a slot
- G+M proposed damage to ventral pathway did not cause deficit in “how”
Define Dissociation (single and double)
One function is absent while another is present
- Single: 1 person
- Double: 2+ people
How did Ganel demonstrate separation of perception and action in non-brain-damage subjects?
Researchers used an illusion that distorts perceived line length and asked subjects to (1) estimate length (what) and (2) grasp the line (how)
- When doing task 1, inaccurate
- When doing task 2, accurate
Define Modules
Brain structures that are specialized to process information about particular types of stimuli
What are 4 examples of Modules?
- Inferotemporal (IT) cortex in monkeys: respond best to faces in
- Fusiform Face Area (FFA): responds best to faces
- Parahippocampal Place Area (PPA): responds best to indoor and outdoor spaces
- Extrastriate Body Area (EBA): responds best to bodies and body parts
