central vision 1
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Lab write up due this Friday
Proposal due Monday March 6
Late reports, one mark out of 20 for each
day late.
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Ch. 11
Vision - central processes
Ultimately visual perception
Also:
Adjust size of the pupil
Direct eyes to the targets of interes
Regulate homeostatic behaviors to L/D cycle
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Primary Visual Pathway
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Primary Visual Cortex
AKA
Striate cortex
Brodmanns area 17 or VI
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Optic Disc
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Blind Spot:
Test your blind spot.
Optic disc is located on the nasal side of theretina.
With both eyes open, information about thecorresponding region of visual space comes
from the temporal side of the contralateralretina.
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Blind Spot
With one eye, blind spot is undetected.
Why?
Visual cortex receptive fields fill in with
cortical mechanisms that integrate
information from the visual field
(somehow).
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Optic Disc
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Optic Chiasm
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x
O ti T t
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Optic Tract
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Decussation
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Ganglion cell axons to lateral geniculate nucleus
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Another target of ganglion cells:
Pretectum co-ordinates pupillary light reflex
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Another target of ganglion cells:
suprachiasmatic nucleus
(Retino-hypothalamic pathway)
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Suprachiasmatic nucleus
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Another target for ganglion cells:
superior colliculus
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Another target for ganglion cells:
superior colliculus
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RETINOTOPIC REPRESENTATION OF
THE VISUAL FIELD
Each eye sees a part of the visual
space that defines its visual field
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VISUAL FIELD
Temporal visual fields are more
extensive than the nasal visual fields
Vision in the peripheral field is mono-
ocular
Most of the rest of the visual field is
seen by both eyes.
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Map is maintained in the LGN
Maintained by the visual cortex
Fovea is in the back of the visual cortex
Peripheral is progressively more anterior
Sensory surface reflects density of
receptors
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Upper visual field
Calcarine
sulcus
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Hubel and Weisel
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Hubel and Weisel
Visual cortex responses using micro-electrodes
Respond ot light/dark bars or edges Only if in a particular orientation
Peak frequency depends on angle,preferred orientation
All edges representations were equallyrepresented
Orientation selective neurons
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Visual Cortex
Simple cells - Spatially distinct on and offzones
Complex cells - receptive field has a mixtureof on and off zones
Length cells - respond to length of a bar thatwas moved across a receptive field
Direction cells - respond to direction of a barmoving across the receptive field.
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Still do not understand the mechanisms
responsible for generating these
selective responses.
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Complex cell
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Complex
Cell
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Binocular vision
Individual LGN neurons are mono-ocular
driven.
How are neurons with different receptivefields arranged within the striate cortex?
A column of cells has similar response
properties
Adjacent columns have similar response
properties.
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Visual Cortex
Composed of repeating units that
contain all the neuronal machinery
necessary to analyze a small region ofvisual space for a variety of different
stimulus attributes.