Visual Pathway Flashcards
What are the lateral geniculate nuclei
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
What is the LGN made up of?
6 layers
1-2 magnocellular layers
3-6 parvocellular layers
Which layers of LGN receive input from ipsilateral eye
2 3 5
What are types of cells in the LGN
X and Y cells
What happens in layers 1 and 2 of LGN
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
What happens in layers 3-6
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
What is the striate cortex? STructure?
Foudn in occipiptal corex
V1 or Brodmann’s 17
hWhat are the layers of the striate cortex
6 layers
Layer II cells synapse with the contralateral visual cortex via corpus callosum
What is the stripe of Gennari
Visiabl layer IV of striate cortex - thickest layer receives efferents from the LGN
Contains many stellate cells
What does layer V of striate cortex do?
Relay to superior colliculus whose connections with the medial longitudinal fasciculus allow coordination of eye movements
What does layer VI of striate cortex do?
Sends efferents to the LGN and contains mainly pyramidal cells
Synpase with gnaglion cells and interneurones
What are the main cell types of the visual cortex?
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
Where does the superior half of the visual field correspond to in the cortex
Infeiror half of retina
Area below the calcarine sulcus
Where does the most anteiorr end of the sulcus correspond to
Peripheral nasal retina - temporal crescent in contralateral eye if lesion
Why is there macular sparing?
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
