Download Occular Dominance Columns

Ocular Dominance Columns
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Binocular Vision
• LGN receive input from both eyes, but
these are in separate layers.
• Individual LGN neurons are monoocular driven.
• Ocular dominance columns in layer IV
of the visual cortex.
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How are neurons with different receptive
fields arranged within the striate cortex?
• A column of cells has similar response
properties.
• Adjacent columns have similar
response properties.
• Same orientation is repeated at approx.
1 mm horizontal intervals (orientation
preference).
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Ocular Dominance Columns
• The striate cortex is composed of
repeating units that contain all the
neuronal components to analyze a
small region of visual space for a variety
of different stimulus attributes.
Ocular Dominance Columns
• Neurons respond to a single eye at the
extreme of a column, middle area
responds to both eyes.
Within the primary visual pathway.
• LGN layers
• Different cell size.
• There are separate functional streams
for conveying information from different
types of retinal ganglion cells to initial
stages of cortical processing
Different cell size.
• MAGNOCELLULAR STREAM: for detecting
rapidly changing stimuli (ventral)
• PARVOCELLULAR STREAM: high acuity and
colour vision (dorsal)
• KONIOCELLULAR STREAM: shares colour
vision with parvocellular stream.
(interlaminar)
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LGN Magnocellular &
Parvocellular Streams
• M ganglion cells and P ganglion cells
terminate in separate layers.
• Synapse onto neurons projecting to
separate strata of striate cortex layer IV.
M ganglion cells
• Large receptive fields
• Axons have fast conduction velocity
• Respond transiently to stimulus
presentation.
P ganglion cells
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•
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Small receptive fields
Slower conduction velocity
Sustained response
Can transmit colour information.
Center/surround, red/green; green/red
Koniocellular Pathway
• Evidence for input from short
wavelength color.
• LGN interlaminar areas