Glossary of SFS - Higher Visual Processing
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- Visual system requires roughly how much of the brain for visual capacity?
- 1/3
- What is the problem of processing visual information?
- The forward problem of optics and the inverse problem of vision.
- Injury to back of the head (occipital lobe) might induce what?
- Visual disturbance or loss
- Pathway of visual tract.
- retina > optic nerve > optic chiasm > optic tract > lateral geniculate nucleus of thalamus > optic radiation to primary visual cortex
- How do human visual abilities differ from a camera?
- We record AND perceive
- Major targets of retinal ganglion cells.
- Retinal recipient nuclei
- 90% of retinal ganglion cells terminate here.
- lGN
- Four locations other than LGN that retinal ganglion cells terminate.
- superior colliculus (5-7%), suprachiasmatic nucleus (circadian), pretectum (pupillary light reflex), and accessory optic system (stabilize one's gaze)
- Rapid, pointing eye movements moderated by tehh superior colliculus.
- saccades
- a. Pupillary light reflex circuit pathway.
b. Out of nearly a million ganglion cells, how many take this route on each side for the reflex?
- a. Photons reach retina > optic nerve > optic chiasm > pretectal olivary nucleus sends fibers to BOTH Edinger-Westphal nuclei > CN III > Ciliary ganglion > ciliary nerves > iris constrictor muscles
b. only a few thousand
- Result of a lesion in the LGN > cortex. Can someone with a cortical lesion act on visual information?
- Complete blindness, but some reflexes can remain. Yes, they can act on visual information, but have no conscious awareness of it.
- Caused by lesions in retina to LGN to primary visual cortex system?
What about lesions in other parts of the cortex?
- Specific visual field defects.
Lesions in other parts of the cortex will cause more subtle visual defects.
- Involves a very limited ability to perform visually guided tasks when there is destruction along the visual tract; in the apparent absence of conscious perception. Will respond to certain visual stimuli, but they claim to see nothing.
- Blindsight
- Lesions here will cause more subtle defects in person's ability to comprehend what they are looking at. Normal visual fields and acuity.
- Extrastriate cortex
- What is:
a. OS
b. OD
- a. oculus sinistra (left eye)
b. oculus dextra (right eye)
- Injury to right optic nerve results in what?
- OD blindness
- Lesion at optic chiasm leads to what?
- bitemporal hemianopia. Lateral half of vision in each eye is knocked out.
- Lesion to right optic tract will result in what?
- left homonymous hemianopia (left half of visual field knocked out in both eyes)
- Lesion to right Meyer's loop will result in what?
- Left superior quadrantanopia (superior lateral quadrant is knocked out equally in both eyes)
- Lesion to visual cortex will result in what?
- Left or right homonymous hemianopia with macular sparing.
- Three other names for primary visual cortex.
- Striate cortex, Area 17, Area V1
- Possible cause of lesions to visual system?
- pituitary tumors
- Mapping in visual cortex.
- Retinotopic map. Most of primary visual cortex is in the calcarine sulus, while the fovea is near the surface. Periphery is deeper.
- Attributed to the nose getting in the way of vision. Allows right eye to see further right than left eye can, and the inverse, etc.
- Right and left monocular crescents
- Most expensive effort in vision.
- analyzing and computing the image
- Part of the retina with a lot more detail than the periphery. Lot more information to analyze. Has a larger, strecthed out retinotopic map in cortex.
- Fovea
- Term describing larger representation of fovea than rest of eye on the visual cortex.
- Cortical magnification factor. Greatest amount of visual work occurs at 0 degrees.
- Names for LARGE and SMALL ganglion cells leaving the retina in a parallel pathway.
- MAGNO (large) and PARVO (small) ganglion cells.
- Ganglion cells not sensitive to color contrast, but have higher sensitivity to low contrast stimuli and temporal frequency, and lower sensitivity to spatial frequency (don't see fine detail.
- M cells
- Ganglion cells that respond to quickly moving objects (high temporal) and only see broad detail (low spatial).
- M cells
- Ganglion cells that have higher sensitivity to spatial frequency, and see color.
- P cells
- Ganglion cells that do not respond to quickly-moving stimuli, but process fine detail.
- P cells
- Ganglion cells that cross.
- 1, 4, 6
- Ganglion cells that do not cross.
- 2, 3, 5
- The two most ventral layers are what type of cell layers? The 4 most dorsal layers are what type of cell layers?
- M-cell layers; P-cell layers
- Is there binoculular computation between M & P cell layers bilaterally?
- NO
- Are most of the synapses on relay cells in the LGN from the retina?
What cells make local connections?
LGN receives inputs from where else?
- No
Interneurons
Brainstem, visual cortex (feedback), and peri-geniculate nucleus
- Are there more interneurons than relay neurons?
- Yes
- Layer 4 of the six visual cortex layers.
- Stria of Gennari. Visual cortex has expanded 4th layer.
- LGN to Area V1 pathway.
- Thalamocortical or geniculostriate pathway.
- Deals with orientation of image, unlike ganglion cells of retina and LGN, which only differentiate between on/off center and surround.
- Area V1
- V1 cells that have discrete excitatory and inhibitory subregions like retinal ganglion cells, but RF subregions are not radially symmetric. Cell doesn't respond to uniform strip of light
- V1 simple cells
- V1 cells that do not have discrete excitatory or inhibitory regions. Selective for orientation. Gerneralize and can be more abstract.
- V1 complex cells
- If you had an ellipse and reversed the pink middle and gray sides, which V1 cells would recognize the difference?
- Simple cells
- While retina > LGN > V1 are obligatory for vision, what allows us to see well?
- Rest of the regions (V2)
- Dorsal stream pathway.
What type of cells does it involve and what do they tell us?
- V1 > V2 > MT > Post. parietal cortex
Magno/M cells. Tells us "where" an object is in space.
- Ventral stream pathway.
What type of cells does it involve and what do they tell us?
- V1 > V4 > Inf. temporal cortex
Involves mostly parvo/P cells and tells us "what" we are seeing.
- A lesion where will result in trouble with landmark discrimination in relation to other objects?
- posterior parietal lobe
- A lesion where will result in trouble telling different shapes apart?
- Inferior temporal cortex
- Cortical area closely associated to V1, higher level of abstraction as it fill in the details from contextual information.
- V2 (has both M and P cells) and is neither ventral nor dorsal.
- Cortical area that is more ventral stream and deals with complex color and form/shape (spirals) properties
- V4
- Cortical area (ventral stream), with high specificity in distinguishing between two faces. Can have large RF, but still high specificity.
- IT - inferior temporal cortex
- Loss of the ability to recognize faces with no corresponding loss of acuity or visual field defects.
- Prosopagnosia
- Cortical area inovlved in motion and perception of motion. Small component of the dorsal stream.
- MT (V5) Middle temporal cortex
- Cortical area inovlved in motion and perception of motion. Small component of the dorsal stream.
- MT (V5) Middle temporal cortex
