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Axons from the retinal ganglion cells...
travel the optic nerves
Information from left visual world is processed by...
right side of the cortex
information from the right visual world is processed by...
left side of the visual cortex
what is a nasal hemiretina?
closer to the nose
what is the temporal retina?
closer to the temples
the nasal hemiretina from one eye and the temporal hemiretina from the other eye...
see the same part of the visual world
point of which some of the axons pf retinal ganglion cells cross
- projection does not cross.
- *stays on the same side
projection crosses the midline of the brain
information from the retina projects to...
the lateral geniculate nucleaus
Lateral Geniculate Nucleus
-region of the thalamus (dicenphalon)
- --receives info from ipsilaeral temporal hemiretina and contralateral nadal hemiretina
- *receive info from enire contralateral visual field
Quote in book
3 stimuli presented in adjecent areas of retina excite adjacent neurons at all levels of system
what regions did Hunel and Wiesel recorded from?
-retinal ganglion cells
--lateral geniculate nucleus of the thalamus
- LAyer 4 cells of the primary visual cortex
***cells from these different regions seemed to respond similarily
what are the layer 4 cells of the primary visual cortex?
layer where axons from the lateral geniculate terminate and synapse on the cortical neurons
who discovered visual receptive fields
Torsten wiesel and david hubel
Visual receptive filed procedure
-record the AP of indiviudal neurons of the visual system
-shine light from a projector on to a specific points on a board
-neurons increased their firing rate when light fell on specific spots
(hubel and wiesel) Cells from these 3 regions seemed to respond similarly (3)
-retinal ganglion cells (output of the retina)
-lateral geniculate nucleus of the thalamus
- -layer IV cells of the primary visual cortex
- *this is layer where axons from lateral geniculate terminate and synapse on to cortical neurons
(striate cortex neurons) 4 properties of visual receptive fields
- -smaller fields in the fovea region than those of periphery
- *helps with acuity at the fovea
-Receptive fields are circular
- -neurons have monocular receptive fields
- *information from only one eye
-excitatory and inhibitory areas of receptive field
two types of center surround responses
-on center and off center
responses of an on-center cell
-there is an on response when a spot of light is shone anywehre in the center of the field
-there is an off response when a spot of light is shone anywhere in the periphery of the field
responses of an off-center celll
-there is an 'off' response when a spot of light is shone anywhere in the center of field
-there is an 'on' response when a spot is shone anywhere in the periphery of the field
one way to maximize firing power of on-center and off-center cell?
- by creating a contrast.
- *the whole circle cannot be light
2 types of cells in visual cortex
simple and complex
description of simple cells (visual cortex) (4)
- -monocular responses
- -receptive fields are not circles but more like straight lines
- -still have anatognistic regions of receptive fields with on/off regions
- -respond best to bars of light or bars of dark
similarities of complex cells of visual cortex to simple cells
- -respond best to bars of lights wth specific orientations
- -unresponsive to diffuse light
difference of complex cells to simple cells
- -larger receptive fields
- -no "antagonistic regions
- *bar of light will respond acorss the entire receptive field
- -respond to movement
perception begins with...
information about light reaching primary visual cortex
Primary visual cortex sends information....
-on to secondary visual cortex amd then to association cortex
- *as info keeps moving along
- **receptive fields become larger
- **neurons respond to more complex stimuli
inforamtion flows to the posterior parietal cortex( visual association cortex)
information flows to the inferotemporal cortex (also visual association cortex)
brief description of dorsal stream
- -appears to be important for determining where stimuli are in space
- *damahe here prevents people from reaching out and grabbing objects
- **but nkow what the object is
brief decription of ventral stream
- -appears to be important for identifying objects
- * no problems reaching for objects
- **do not know what is is
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