Quiz 2 Flashcards
What is excitatory signaling in bipolar cells?
It speeds up the firing rate of bipolar cells.
What is inhibitory signaling in bipolar cells?
It slows down the firing rate of bipolar cells.
What is neural convergence?
It is the synapsing of a number of neurons onto one neuron.
What are the steps of neural convergence?
- Light entering the eye triggers a photochemical reaction in rods and cones at the back of the retina. 2. The chemical reaction activates bipolar cells. 3. Information is sent to the visual cortex via the thalamus.
Which has more convergence, rods or cones?
Rods.
How do receptor, bipolar, and ganglion cells pass signals?
Vertically.
How do horizontal and amacrine cells pass signals?
Laterally.
What does a bipolar cell receive signals from?
A bipolar cell gets a signal from a photoreceptor and two neighboring horizontal cells.
Are all vertical signals excitatory or inhibitory?
Excitatory.
Are all lateral signals excitatory or inhibitory?
Inhibitory.
What is lateral inhibition?
It is the sending of inhibitory signals across the retina.
True or False: Rods have more convergence than cones.
TRUE.
Increased convergence leads to greater sensitivity but poorer what?
Detail.
What is the phenomenon of lateral inhibition demonstrated through?
It can be demonstrated through the appearance of mach bands where you perceive a darker band on the edge of the lighter side because there is more inhibition coming from the darker side.
How is the pattern of light from the left visual field processed?
It is processed by the right side of each eye and the lateral geniculate nucleus (LGN) and the right primary visual cortex.
Where do most fibers from the optic nerve project?
To the LGN, but about 10% project to the superior colliculus.
What is retinotopic mapping?
It maintains the spatial relationship from the retina to the LGN to the primary visual cortex.
What is the function of the frontal lobe?
Taste.
What is the function of the temporal lobe?
Hearing and smell.
What is the function of the parietal lobe?
Touch.
What is the function of the occipital lobe?
Vision.
How many layers do LGN cells have?
6 layers: 2 inner and 4 outer.
What do magno cells detect?
Movement (rods).
What do parvo cells detect?
Details (cones) in the fovea.
What is the structure of the primary visual cortex (V1)?
It has six layers, LGN projects to layer 4, and layer 4 projects to layers 3 and 2.
What types of cells are found in V1?
No center surround, simple, complex, and hypercomplex cells.
What can simple cells detect?
Location and orientation but cannot detect movement.
What do complex cells respond to?
Moving lines/edges and are sensitive to the direction of motion but not sensitive to position.
What do hypercomplex cells respond to?
Moving lines or edges of specific length.
What is visual form agnosia?
A deficit in perceiving simple forms due to damage to the ‘what’ system in the temporal lobe.
What is visual agnosia?
A failure in object recognition.
What is optic ataxia?
Damage to the dorsal stream (parietal lobe) that leads to a failure to discriminate between objects and not being able to group them accurately.
Onto what two structures do the ganglion cells synapse?
LGN and primary visual cortex.
How is visual information processed when both eyes take in light from the right visual field?
The left visual field is processed by the right side of the brain and vice versa. 90% of optic nerve fibers project to the lateral geniculate nucleus, while 10% goes to the superior colliculus.
How can the four types of ganglion cells in the frog be described?
Edge detector, bug detector, moving edge detector, dimming detector.
What is a receptive field?
An area on the retina that, when stimulated, changes the activity of the cell.
Distinguish between P (parvo) and M (magno) cells.
Parvo cells have smaller receptive fields, respond to sustained stimulus, and inform about detail. Magno cells have larger receptive fields, respond to transient stimulus, and are important for detection of movement.
What brain area is damaged in blindsight?
The primary visual cortex.
What is a double dissociation?
Two different functions involve two different mechanisms. Damage to structure A impairs function A but not B, and damage to structure B impairs function B but not A.
How was a double dissociation shown with monkeys?
Damage to the temporal lobe removed object discrimination, while damage to the parietal lobe removed landmark discrimination.
Where is evidence for face processing found?
In the area of the temporal lobe, ventral pathway.
