Visual Pathway Flashcards

1
Q

What are the lateral geniculate nuclei

A

Paired thalamic nuclei
Retinal galngion cells synpase with fibres form visual cortex

REtinotopically mapped with information from usperior and inferior retina to the medial aspct

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2
Q

What is the LGN made up of?

A

6 layers

1-2 magnocellular layers

3-6 parvocellular layers

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3
Q

Which layers of LGN receive input from ipsilateral eye

A

2 3 5

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4
Q

What are types of cells in the LGN

A

X and Y cells

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5
Q

What happens in layers 1 and 2 of LGN

A

MAgnocellular ganlgionc cells are linked to rods
Large, fast and deal with motion detection and luminance - synapse with T cells in layers 1 and 2

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6
Q

What happens in layers 3-6

A

Parcovellular P ganglion cells are small slow and linked to cones mainly at fovea
Deal with spatial resolution an dcolour
Synapse with X cells in layers 3-6

These layers fuse anteirorly forming 4 ventral layers of LGN

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7
Q

What is the striate cortex? STructure?

A

Foudn in occipiptal corex
V1 or Brodmann’s 17

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8
Q

hWhat are the layers of the striate cortex

A

6 layers

Layer II cells synapse with the contralateral visual cortex via corpus callosum

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9
Q

What is the stripe of Gennari

A

Visiabl layer IV of striate cortex - thickest layer receives efferents from the LGN
Contains many stellate cells

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10
Q

What does layer V of striate cortex do?

A

Relay to superior colliculus whose connections with the medial longitudinal fasciculus allow coordination of eye movements

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11
Q

What does layer VI of striate cortex do?

A

Sends efferents to the LGN and contains mainly pyramidal cells
Synpase with gnaglion cells and interneurones

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12
Q

What are the main cell types of the visual cortex?

A

Concentric cells - centre surround receptive field
Simple cells in IV with receptive fields in parallel bands
Complex cells with binocular input in III and V which response to stimulus of specific orientation moving in specific direction
Hypercomplex cells - respoding to stimuli of specific length, orientation and direction

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13
Q

Where does the superior half of the visual field correspond to in the cortex

A

Infeiror half of retina
Area below the calcarine sulcus

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14
Q

Where does the most anteiorr end of the sulcus correspond to

A

Peripheral nasal retina - temporal crescent in contralateral eye if lesion

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15
Q

Why is there macular sparing?

A

Posterior end of sulcus lies at the region between the MCA and PCA territory and the area of cortex devoted to the macula is largeW

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16
Q

What is the prestriate cortex?

A

Areas V3 to V8

V2 - thin (colour) thick (motion)
V3 - selective for form
V4 - colour, line orientation, shape detection
V5- motion and direction