Midterm 2: Chapter 4 Flashcards
The visual signals from both eyes leave the back of the eye in the optic nerve and meet at a location called?
Optic Chiasm
Where do some of the fibers cross to the opposite side of the brain from the eye they came from?
Optic chiasm
What does it mean by the brain is contralateral?
Each hemisphere of the brain responds to the opposite side of visual field
Anything to the right of the point of central focus is the _________ visual field.
right
Anything to the left of the point of central focus is the _________ visual field.
Left
Which hemisphere is the right visual field processed by?
Left hemisphere
Which hemisphere is the left visual field processed by?
Right hemisphere
True or false? Both eyes cannot see both visual fields
FALSE; both eyes CAN see both visual fields
Where do 90% of signals from the retina proceed to?
LGN (lateral geniculate nucleus)
Where do 10% of signals from the retina proceed to?
Superior colliculus
a structure in the thalamus that relays visual information from the retina to the primary visual cortex
- receives more signals from the cortex than from the retina.
LGN
- involved in controlling eye movements
- a midbrain structure that integrates sensory information to help orient the head and eyes toward stimuli.
Superior colliculus
- Backward flow of information
- involved in. regulation of info flow, the idea that the info the LGN recieves back from the brain may play a role in determining which info is sent up to the brain.
Feedback
The occipital lobe; the place where signals from the retina and LGN first reach the cortex.
Visual receiving area/ V1/ Striate Cortex
Explain pathway of the eye
Signals leave the eye and cross at the optic chiasm, make a stop in the LGN, and then proceed to the visual cortex.
- cells with side-by-side receptive fields
- respond to bars, but to bars of particular orientations
- respond to small spots of light or to stationary stimuli
Simple cortical cells
- Determined by measuring the responses of a simple cortical cell to bars with different orientations.
- The relationship between orientation and firing is indicated by this.
Orientation Tuning Curve
- Respond best to bars of a particular orientation
- respond only when a correctly oriented bar of light moves across the entire receptive field.
Complex cells
- Fires to moving lines of a specific length or to moving corners or angles.
- respond best to bars of a certain length that are moving in a particular direction.
End-stopped cells/ feature detectors
What responds best to spots of light?
Retinal ganglion cells
Center-surround receptive field. Responds best to small spots but will also respond to other stimuli.
Ganglion cell
Center-surround receptive fields are very similar to the receptive field of a ganglion cell.
LGN
Excitatory and inhibitory areas arranged side by side. Responds best to bars of a particular orientation.
Simple cortical cell
Responds best to the movement of a correctly oriented bar across the receptive field. Many cells respond best to a particular direction of movement.
Complex cortical cells
Responds to corners, angles, or bars of a particular length moving in a particular direction.
End-stopped cortical cells
What happens when we view a stimulus with a specific property?
Neurons tuned to that property fire.
Firing causes neurons to eventually become fatigued or adapt
1. the neuron’s firing rate decreases
2. the neuron fires less when that stimulus is immediately presented again.
Selective Adaption
Why is adaption selective?
because only the neurons that were responding to verticals or near-verticals adapt, and neurons that were not firing do not adapt.
The minimum intensity difference between two adjacent bars that can just be detected.
Grating’s contrast threshold
- measure a person’s contrast threshold to gratings with a number of different orientations
- Adapt the person to one orientation by having the person view a high-contrast adapting stimulus for a minute or two.
- Remeasure the contrast of all the test stimuli presented in step 1.
How to measure the effect of selective adaption to orientation.
If an animal is reared in an environment that contains only certain types of stimuli; then neurons that respond to these stimuli will become more prevalent.
- a long-term effect
Selective Rearing
The idea that the response properties of neurons can be shaped by perceptual experience
- rearing an animal in an environment that contains only vertical lines should result in the animal’s visual cortex having simple cells that respond predominantly to verticals.
Neural plasticity
found that the cat’s vision appeared significantly impaired when the cats were placed in a furnished room. They could not detect edges or objects oriented in the opposite direction than that they had previously been exposed to, amongst other visual impairments.
Blakemore and Cooper
Electronic map of the retina on the cortex. It involves using two coordinates, eccentricity and polar angle, to identify the representation of a location in the visual field on the cortex.
Retinotopic map
Why is the spacing of locations off in a person’s retinotopic map?
The spatial representation of the visual scene on the cortex is distorted, with more space being allocated to locations near the fovea than to locations in the peripheral retina.
Apportioning of a large area on the cortex to the small fovea is called?
cortical magnification
Striate cortex is organized into _________ _________ that are perpendicular to the surface of the cortex.
Location columns
Why are location columns used?
so that all of the neurons within a location column have their receptive fields at the same location on the retina.
What did Hubel and Wiesel discover with their electrode experiment? (2 things)
- Neurons along this track had receptive fields with the same location on the retina, but these neurons all preferred stimuli with the same orientation.
- Adjacent orientation columns have cells with slightly different preferred orientations.
Cortex is organized into ___________ ___________, with each column containing cells that respond best to a particular orientation.
Orientation columns
What is the size of one location column?
1-mm
- A location column with all of its orientation columns
- recieves info about all possible orientations that fall within a small area of the retina.
Hypercolumn
Columns covering the entire visual field
Tiling
Where the visual signal proceeds to after the V1; areas known as V2, V3, V4, and V5.
Extrastriate cortex
Refers to the destruction or removal of tissue in the nervous system.
Ablation
- a task that involves distinguishing between two objects, often by identifying the difference between them.
- the monkeys are presented with an unfamiliar object. They are then presented with this object and a new object. The monkeys task is to pick the newer object showing that they recognize the original object. If they choose the correct object they are rewarded.
Object Discrimination Problem
- a task that assesses an animal’s ability to use spatial information to find a target by using a landmark as a reference
- The monkey’s task was to remove the cover of the food well that was closest to the “landmark” (a tall cylinder)
Landmark Discrimination Problem
After the ablation of their temporal lobe, was object discrimination easier or harder to perform?
Harder
The pathway that reaches the temporal lobes is responsible for?
Determining an object’s identity.
Striate cortex to the temporal lobe
“What” pathway
The pathway that leads to the parietal lobe is responsible for?
Determining an object’s location
Pathway leading from the striate cortex to the parietal lobe
“Where” pathway
The “what” pathway
Ventral pathway
The “where” pathway
Dorsal pathway
Refers to the back or upper surface of the brain
Dorsal
Refers to the lower part of the brain
Ventral
Where can the cortical ventral and dorsal streams be traced back?
back to the retina and LGN.
What did Milner and Goodale propose about the dorsal stream?
Dorsal stream is for taking action, such as picking up an object.
The _________ stream provides information about “how” to direct action with regard to a stimulus.
Dorsal
How can we understand the effects of brain damage?
By determining double dissociations.
Involves 2 people: one person has damage to one area of the brain, causes function A to be absent while function B is present. In the other person, damage to another area of the brain causes function B to be absent while function A is present.
Double Dissociation
What is the dorsal pathway?
The “how” pathway/ “action” pathway
- area in the temporal lobe
- a large part of the visual cortex in the brain that’s responsible for recognizing objects, faces, and scenes
Inferotemporal (IT) cortex
Why are neurons at the apex of the “what” stream in the IT cortex have the largest receptive fields?
There’s a receptive field size that continues through the “what” stream.
An area associated with forming and storing memories.
Hippocampus
Effect of stimulating outside the receptive field
Contextual modulation
