Bio 8

travel the optic nerves

right side of the cortex

left side of the visual cortex

closer to the nose

closer to the temples

see the same part of the visual world

optic chiasm

• projection does not cross.
• *stays on the same side

projection crosses the midline of the brain

the lateral geniculate nucleaus

-region of the thalamus (dicenphalon)

• --receives info from ipsilaeral temporal hemiretina and contralateral nadal hemiretina
• *receive info from enire contralateral visual field

3 stimuli presented in adjecent areas of retina excite adjacent neurons at all levels of system

-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

layer where axons from the lateral geniculate terminate and synapse on the cortical neurons

Torsten wiesel and david hubel

-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

-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

• -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

-on center and off center

-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

-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

• by creating a contrast.
• *the whole circle cannot be light

simple and complex

• -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

• -respond best to bars of lights wth specific orientations
• -unresponsive to diffuse light

• -larger receptive fields
• -no "antagonistic regions
• *bar of light will respond acorss the entire receptive field
• -respond to movement
• -BINOCULAR

-more numerous 

information about light reaching primary visual cortex

-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)

• -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

• -appears to be important for identifying objects
• * no problems reaching for objects
• **do not know what is is