Term
| Recap: pretectal nucleus responsible for what? |
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Definition
| pupil (sphincter) control via edinger westphal nucleus |
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Term
| difference between action potential and graded potential? |
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Definition
AP: yes/no response. stimuli must reach a certain point. travel further. amacrine/ganglion cells.
GP: level of activity of a cell. travels shorter distance. |
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Term
| extracellular recordings vs Evoked potentials? |
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Definition
ER: measures action potential of a few cells using high impedence electrode.
EP: measures graded potential of a group of cells (local brain activity) using low impedence electrode |
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Term
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Definition
Layer 1+2: magno input.
Layers 3-6: parvo input
in between, koniocellular input.
layers 2,3,5--> ipsilateral eye.
Layers 1,4 ,6---> contralateral eye |
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Term
magno/parvo input into V1 layers?
from v1, outputs? |
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Definition
magno: 4Ca > 4B (motion)
parvo: 4A + 4Cb>2,3 (colour, form)
L2,3,4B: other cortical area
L5,6: deeper structures |
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Term
| what is cortical magnification? |
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Definition
more foveal input is represented in v1 than nonfoveal. central 2.5degrees is represented by 25% of V1.
ie 1 deg @ fovea -->15mm in V1.
1deg at 15eccentricity--> 1mm of V1 |
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Term
| properties of cytochrome oxidase blobs ? |
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Definition
| 2 blobs/column. colour coded. no orientation sensitivity. |
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Term
| outline flow of info from parvo/magno thru v1> v2 etc |
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Definition
Parvo> v1> interstripes + thin stripes V2 > V4 colour > IT
Magno > v1 > thick stripes V2 > V3, V5 > MST > Parietal cortex |
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Term
| amblyopia: why does amblyopia develop? what affects the severity of amblyopia? |
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Definition
result of abnormal input to the cortex, so neural connections do not develop properly. is not due to deprivation but due to competition between the 2 sets of synaptic input
early deprivation > deprivation when older
period of deprivation not impt, age of deprivation is vital
patching must be done w/i critical period
no patching = no reversal
v1: respond to lower SF. poor response due to deterioration in number of synapses
LGN: physiologically normal but physically abnormal (small and pale) as they have less v1 cells to support. |
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Term
| eye hand coordination: temporal interactions |
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Definition
1)eye leads hand using visual info for online adjustments. is 200ms slow, mainly foveal. (depends on context, complexity and detail of environment, whether person is still or moving)
2) gaze locking: 2nd saccade delayed until hand reaches 1st target
3)first hand movement is delayed until eye is available to guide it. |
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Term
| eye hand coordination: spatial interactions |
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Definition
| magnitude of hand movement and saccades is related WHEN HAND IS NOT SEEN. eye moves more than hand. |
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Term
| Eye hand coordination: how is accuracy maintained without compromising speed? |
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Definition
Visual feedback is accurate but slow.(200ms) faster mechanisms include
1) ocular proprioception: guides hand to 'felt' position of eye, 100ms
2) hand proprioception: felt location of hand influences accuracy of saccades (eg, reading text that is moving laterally)
3)Extraretinal signals: Efference copy is fast but inaccurate when sustained. |
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Term
| when the eye and hand move together.. |
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Definition
| saccades are faster and more accurate + hand movements are inititated faster. |
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