Week 3 Flashcards
Convergence can be either excitatory or inhibitory. True or false
True
Which receptors excite ESPS the neuron at point B?
3, 4, 5
Which receptors converge on inhibitory neurons ISPS that reduce activity at B.
1,2, 6, 7
Presenting light to the center of an Excitatory center, inhibitory-surround receptive field:
More action potentials in the ganglion cell.
Presenting light to the center of an inhibitory center, excitatory surround receptive field:
Fewer action potentials in the ganglion cell.
Summation of excitatory and inhibitory connections in the retina creates _______ for ganglion cells and other visual system neurons.
Receptive fields
Edge enhancement
An increase of perceived intensity of borders in visual field
What happens in Chevreul Illusion?
People tend to see, enhance lightness, and darkness at the borders between light and dark areas.
Why does edge enhancement happen?
- Center-surround cells near the border get different input than those in the middle.
- Because of the effect of lateral inhibition in center-surround receptive fields.
When an image is focused on the retina, in which part of the retina should you have the greatest amount of lateral inhibition?
A. Macula.
B. Fovea.
C. Blindspot.
D. Periphery.
E. All areas with receptors should be roughly equal.
D. There should be greater convergence in the rods of the periphery.
Lateral inhibition alone fails to explain the Chevreul illusion in some situation. What does that suggest?
The effect goes beyond local lateral inhibition. It is only part of the story we need to look further on in the brain for more answers.
Where do retinal signals go?
Approximately 1 million ganglion cells, send axons out of each retina. These axons formed the optic nerve.
Approximately 10% of these go to the superior colliculus , to eat with orienting and multi sensory responses.
About 90% go to the lateral geniculate nucleus (LGN) of the thalamus.
About how many ganglion axons go to each LGN? how many axons go to the visual cortex?
900,000
360,000
Items in the visual fiend go to the _____ side of both retina.
Opposite
Signals from each hemiretina go to the LGN on the _____ side.
Same (ipsilateral)
Each LGN has ___ layers
6
Which LGN layers receive signal from the same eye?
2,3,5
Which LGN layers receive signals from the opposite eye.
1,4,6
Magnocellular Pathway (M-cells)
which layers? What do they do?
Layers 1 and 2
Transmit info of motion and depth.
Parvocellular pathway (P-cells)
Which layers, what do they do?
Levels 3 - 6
Contain info about detail and color
koniocellular pathway
Which layers, what do they do?
In-between layers
involved with color vision
Signals received in the right LGN must have come form:
A. The right eye
B. The left eye
C. The right visual field
D. the left visual field
D The left visual field
Spatial Maps
Both the retina and the LGN organize activity by spatial maps
Retinotopic Map
Each place on the retina corresponds to a place in the LGN
Use single-cell recordings to determine the location of the corresponding neuron in the LGN
