1037 lines
30 KiB
Markdown
1037 lines
30 KiB
Markdown
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## Brain damage and visual perception
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<div><img src="tmp/2015-09-1116.47.12_3eb196a.png" height="100px"><figcaption></figcaption></div>
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<div><img src="tmp/ScreenShot2015-09-11at5.11.54PM_241cf9a.png" height="100px"><figcaption></figcaption></div>
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Note:
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Let’s begin by going discussing one of the fantastic true stories told by the famous NYC neurologist, Oliver Sacks, who passed away just a few months ago and who weaved engaging clinical accounts and wrote a number of best selling books regarding cases of patients having extraordinary behaviors that resulted from strange or unknown neurological disorders including this one called The Man Who Mistook his Wife for a Hat. —>Indeed one of these accounts was about a man who actually mistook his wife’s face for a hat. This man, who was an accomplished musician and teacher at a school of music had developed trouble seeing faces and recognizing many types of objects in general as a result of degeneration in the visual system, likely from a stroke or something.
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…these types of stories summarize a large bit of what neuroscience is about— understanding fundamental circuits that comprise brain function and animal behavior as well as the dually fascinating and devastating consequences that occur when the formation of those fundamental circuits goes awry.
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---
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## Brain damage and visual perception
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* The patient (‘Dr. P’):
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* good visual acuity & color vision
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* good recognition of abstract geometric objects (cubes, spheres, etc)
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* Trouble recognizing friends, family, pupils
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* Trouble recognizing complex objects
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*
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* Describing a rose: “About six inches in length. A convoluted red form with a linear green attachment”
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* Describing a glove: “A continuous surface, infolded on itself. It appears to have five outpouchings”
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👵🏻
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🎩
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2016-02-16 12:29:41
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Note:
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Let’s begin by going discussing one of the fantastic true stories told by the famous NYC neurologist, Oliver Sacks, who passed away just last summer and who weaved engaging clinical accounts and wrote a number of best selling books regarding cases of patients having extraordinary behaviors that resulted from strange or unknown neurological disorders including this one called The Man Who Mistook his Wife for a Hat. —>Indeed one of these accounts was about a man who actually mistook his wife’s face for a hat. This man, who was a well regarded and accomplished musician and teacher at a NY school of music had developed trouble seeing faces and recognizing many types of objects in general as a result of degeneration in the visual system, likely from a stroke.
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This patient (let’s call him Dr. P)… was cognitively sharp, had good vis…
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Hard time
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visual agnosia, prospognosia, lesion somewhere in temporal lobe of the cerebral cortex for reasons we will hopefully discover partially by the end of today’s class.
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For him the visual world was a series of lifeless abstractions, seeing and describing the world almost the way a machine would see it without grasping the big picture.
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…these types of stories summarize a large bit of what neuroscience is about— understanding fundamental circuits that comprise brain function and animal behavior as well as the dually fascinating and devastating consequences that occur when the formation of those fundamental circuits goes awry.
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---
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## Central visual pathways: retinal targets
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* The retina projects to multiple areas in the brain. Each area is specialized for different functions.
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* Dorsal lateral geniculate nucleus (dLGN)- located in the thalamus- receives visual info from retina and sends it to the visual cortex. Most important visual projection with respect to visual perception.
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* Pretectum-located at midbrain-thalamus boundary. Responsible for pupillary light reflex.
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* Superior colliculus-in midbrain, coordinates head and eye movements.
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* Suprachiasmatic nucleus- in hypothalamus-involved in day night cycles.
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Note:
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Last time
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---
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## Title Text
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*
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The human visual system
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* Hubel, 1988
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<div><img src="tmp/droppedImage_66fa50b.pdf" height="100px"><figcaption></figcaption></div>
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Note:
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The output neurons of the eye-- the retinal ganglion cells-- form synaptic connections in two visual centers the lateral geniculate nucleus and the superior colliculus.
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And the geniculate neurons have in turn formed synaptic connections with the visual cortex, thus forming the basic visual pathway from the eye to the cerebral cortex.
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---
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## Title Text
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[http://courses.pbsci.ucsc.edu/mcdb/bio125/Animation12-01VisualPathways.mov](http://courses.pbsci.ucsc.edu/mcdb/bio125/Animation12-01VisualPathways.mov)
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<div><img src="tmp/posterImage_82a0fa4.png" height="100px"><figcaption></figcaption></div>
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Note:
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---
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## Some important visual system terms:
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*
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* Optic disc, optic nerve- All the retinal ganglion cell (RGC) axons exit the eye at the optic disk (results in a blind spot) and form a big myelinated nerve called optic nerve (cranial nerve II).
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* Optic chiasm- where the optic nerve enters the brain, at the base of the hypothalamus.
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* Optic radiation- portion of the internal capsule (connection between thalamus and cortex) containing the axons from dLGN that project to the visual cortex
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* Primary visual cortex (V1), area 17, striate cortex
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Note:
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finger test
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---
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## Title Text
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The human visual system
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<div><img src="tmp/Neuroscience5e-Fig-12.01-0_8768474.jpg" height="100px"><figcaption></figcaption></div>
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Note:
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---
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## Title Text
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The human visual system
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<div><img src="tmp/posterImage1_9d2e77e.png" height="100px"><figcaption></figcaption></div>
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Note:
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---
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## The pupillary light reflex
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* Light hits retina, sends out axons to both sides of brain that go to the pretectum.
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* Pretectal neurons project to contra- and ipsi-lateral Edinger-Westphal nuclei (in midbrain).
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* Edinger-Westphal nucleus projects to the ciliary ganglion (PNS).
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* Ciliary ganglion projects to the constrictor muscle in the iris. Shining light in one eye leads to constriction of both eye’s muscles.
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[- atropa belladona](https://en.wikipedia.org/wiki/Atropa_belladonna)
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- ‘deadly nightshade’
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* : atropine
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* : mydriasis
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* : dilation of the pupil
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<div><img src="tmp/ScreenShot2015-11-03at9.08.02AM_856e425.png" height="100px"><figcaption></figcaption></div>
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Note:
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---
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## Circuitry responsible for the pupillary light reflex
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Typical test question: Where is the site of injury if shining a light into the left eye
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causes both eyes to constrict but shining light into the right eye does not
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cause either eye to constrict?
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[http://library.med.utah.edu/kw/animations/hyperbrain/parasymp_reflex/reflex.html](http://library.med.utah.edu/kw/animations/hyperbrain/parasymp_reflex/reflex.html)
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Neuroscience 5e Fig. 12.2
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<div><img src="tmp/Neuroscience5e-Fig-12.02-1R_fe93727.jpg" height="100px"><figcaption></figcaption></div>
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Note:
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answer: right optic nerve
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---
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## Title Text
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Intrinsically photosensitive RGCs (containing melanopsin) are required for day/night activity cycles
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<div><img src="tmp/image_3a9dca9.png" height="100px"><figcaption></figcaption></div>
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<div><img src="tmp/image1_d74352b.png" height="100px"><figcaption></figcaption></div>
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Note:
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---
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## The spatial relationships among the RGCs are maintained in their targets.
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* Referred to as visual maps or topographic maps.
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* Images are inverted and left-right reversed as they are projected onto the retina through the lens.
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* The left half of the visual world is represented in the right half of the brain and vice versa (compare to somatosensory system).
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* Because humans are binocular, some inputs from each eye project ipsilaterally and some contra-laterally.
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Note:
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---
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## Title Text
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* Hubel, 1988
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The visual pathway– retinotopy
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retina
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superior
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colliculus,
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dLGN,
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visual cortex
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<div><img src="tmp/droppedImage1_951ed66.pdf" height="100px"><figcaption></figcaption></div>
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<div><img src="tmp/retinotopic_mapping_80f68b4.jpg" height="100px"><figcaption></figcaption></div>
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Note:
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Neighboring retinal ganglion cells in the eye detect changes in contrast from similar portions of the visual field, thus forming a 2D map of visual space in the retina. This spatial representation of objects in the retina is then projected onto -->multiple down stream visual areas, so that maps of retinal topography, or retinotopy, are maintained at multiple levels in the visual system.
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Other visual functional organization that is present at birth includes maps of ocular dominance, where the responses of neuronal groups is dominated by that of one eye or the other and orientation selectivity where the responses of neighboring neurons is dominated by high contrast edges of particular orientation.
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---
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## Title Text
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The visual scene is inverted on the retina
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<div><img src="tmp/image2_33f6059.png" height="100px"><figcaption></figcaption></div>
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<div><img src="tmp/image3_aa4d6a4.png" height="100px"><figcaption></figcaption></div>
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Note:
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or vicious little cujo
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## Binocular vision
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* There is an overlap in visual fields, such that most objects are seen by both eyes.
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* Objects in the left visual field are seen by the nasal retina of the left eye and the temporal retina of the right eye.
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* Objects on extreme periphery are seen only by the nasal retina on that side.
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* Nasal retinal derived axons cross the midline at the optic chiasm (contra lateral) and temporal retinal axons do not cross at the chiasm (ipsilateral).
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* Images in the left visual field project onto the nasal retina of the left eye and the temporal retina of the right eye. These go to the same side of the brain. Therefore the left visual field is mapped onto the right side of the brain.
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* The visual map is maintained all the way to V1. The two halves of the visual fields only merge after getting connections from the other half through the corpus callosum.
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Note:
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humans have binocular vision, such that there is overlap…
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this is crucial for stereopsis, or depth perception (finger disparity)
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---
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## Projection of the visual field onto the retina
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Neuroscience 5e Fig. 12.3
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<div><img src="tmp/Neuroscience5e-Fig-12_426bcfd.jpg" height="100px"><figcaption></figcaption></div>
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<div><img src="tmp/Neuroscience5e-Fig-12.03-1R_3b74ee3.jpg" height="100px"><figcaption></figcaption></div>
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Note:
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So now lets go over the projection of the visual field on to the retina in a little more detail that our cujo example a minute ago.
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---
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## Title Text
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Binocular visual field
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Neuroscience 5e Fig. 12.4
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<div><img src="tmp/Neuroscience5e-Fig-12.04-0_734d7ac.jpg" height="100px"><figcaption></figcaption></div>
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Note:
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Projection of the Binocular Field of View Relates to Crossing of Fibers in Optic Chiasm
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---
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## Title Text
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Binocular visual field
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[http://courses.pbsci.ucsc.edu/mcdb/bio125/Animation12-01VisualPathways.mov](http://courses.pbsci.ucsc.edu/mcdb/bio125/Animation12-01VisualPathways.mov)
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<div><img src="tmp/posterImage2_e582032.png" height="100px"><figcaption></figcaption></div>
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Note:
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---
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## Title Text
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* At the optic chiasm, visual information from the two sides of the head cross.
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* In animals with eyes on the sides of the head, the entire visual field for each side is sent to the opposite side of the brain (to the tectum).
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* In forward-looking animals, the visual image is split
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* An object on the right side of the visual field is seen by both left hemi-retinae (but not by the right hemi-retinae). The optic nerves leave the retinae, and at the optic chiasm, the two left hemi-retinae projections go left, while the two right hemi-retinae go right.
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Fig 16-2 Neurobiology,
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by Gary G. Matthews, Blackwell Science
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Binocular visual field: species differences
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<div><img src="tmp/16-2_ae0f019.jpg" height="100px"><figcaption></figcaption></div>
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Note:
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dev book
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---
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## The human visual system
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|||
|
|
|
|||
|
|
|
|||
|
|
LGN
|
|||
|
|
|
|||
|
|
<div><img src="tmp/image_4e05bc5.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Lateral geniculate nucleus (LGN)
|
|||
|
|
|
|||
|
|
* 90% of the retinal axons go to the dLGN in the thalamus
|
|||
|
|
* dLGN projects to visual cortex (striate cortex).
|
|||
|
|
* Contains 6 layers, that are specific with respect to eye (ipsi vs contra) and with respect to type of ganglion cell— magnocellular (detects gross shape and movement) and parvocellular (form and color).
|
|||
|
|
* Layers align in order to align visual fields.
|
|||
|
|
* Each dLGN receives input from 1 or 2 RGCs therefore like RGCs there also have center-surround responses that are either on or off.
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Laminar organization of the LGN
|
|||
|
|
|
|||
|
|
* Neurons along the projection line see the same point in space
|
|||
|
|
* But neurons in different layers are receiving info from different types of RGCs.
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
<div><img src="tmp/image4_a0246d3.png" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Laminar organization of the LGN: segregation of optic tract inputs
|
|||
|
|
|
|||
|
|
* Each LGN layer is eye-specific
|
|||
|
|
* The projections from the retinal ganglion cells maintain the field of view as it was seen - this is called a retinotopic map. The LGN contains 6 layers of cell bodies; each layer receives input from only one eye. The two most ventral layers receive M (magno) ganglion cell inputs, while the other 4 receive P (parvo) inputs.
|
|||
|
|
|
|||
|
|
<div><img src="tmp/lgn_a1d8674.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
what is parvo and magnocellular? Different subtypes of RGCs that we’ll cover more in just a minute…
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Visual cortex
|
|||
|
|
|
|||
|
|
* The first point in the central visual pathway where the receptive fields of cells are significantly different from those of the retina.
|
|||
|
|
* located in occipital lobe near the parieto-occipital sulcus.
|
|||
|
|
* There is topographic organization of each visual hemifield.
|
|||
|
|
* Upper visual field is represented below the calcarine sulcus, the lower field above the calcarine sulcus.
|
|||
|
|
* Superior and inferior visual fields take different routes to the visual cortex. Meyer’s loop, where superior axons diverge and go into temporal lobe before going to occipital lobe
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Title Text
|
|||
|
|
|
|||
|
|
<div><img src="tmp/posterImage3_3eec61e.png" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Projection to cortex
|
|||
|
|
|
|||
|
|
* The visual field is projected in a retinotopic fashion.
|
|||
|
|
* The right visual field is projected onto the left cortex, while the left visual field is represented on the right..
|
|||
|
|
* The region of the fovea, because of its high sensitivity and density of cones, is represented by a huge amount of the cortex.
|
|||
|
|
|
|||
|
|
<div><img src="tmp/Fig27-9_e1cd31a.png" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
Incr representation sound familiar? think of hand and lip representation in human somatosensory cortex we discussed a couple classes ago…
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Visuotopic organization in the right occipital lobe
|
|||
|
|
|
|||
|
|
* PN12060.JPG
|
|||
|
|
|
|||
|
|
Neuroscience 5e Fig. 12.5
|
|||
|
|
|
|||
|
|
<div><img src="tmp/Neuroscience5e-Fig-12.05-1R_745c746.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Optic radiation paths to the visual cortex
|
|||
|
|
|
|||
|
|
Lower visual field (dorsal retina)
|
|||
|
|
|
|||
|
|
Upper visual field- ventral retina
|
|||
|
|
|
|||
|
|
(c) 2001 Sinauer Associates, Inc.
|
|||
|
|
|
|||
|
|
<div><img src="tmp/PN12070_dc925a2.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Visual field defects
|
|||
|
|
|
|||
|
|
* The spatial relationships in the retina are maintained in the brain…
|
|||
|
|
* Careful analysis of the visual field defects of a patient can often indicate where brain damage is located.
|
|||
|
|
* Anopsias— relatively large deficits
|
|||
|
|
* Scotomas— smaller deficits.
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Visual field deficits resulting from damage along the primary visual pathway
|
|||
|
|
|
|||
|
|
Black means blind
|
|||
|
|
|
|||
|
|
Blue means see
|
|||
|
|
|
|||
|
|
Neuroscience 5e Fig. 12.6
|
|||
|
|
|
|||
|
|
Blindness in R eye
|
|||
|
|
|
|||
|
|
Bitemporal hemianopsia
|
|||
|
|
|
|||
|
|
L homonymous hemianopsia
|
|||
|
|
|
|||
|
|
Upper quadrant hemianopsia
|
|||
|
|
|
|||
|
|
Homonymous hemianopsia with macular sparing
|
|||
|
|
|
|||
|
|
<div><img src="tmp/Neuroscience5e-Fig-12.06-0_b7750c9.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## The columnar organization of visual cortex
|
|||
|
|
|
|||
|
|
* The visual cortex is layered. Each layer has stereotypical inputs and outputs. LGN projects to layer 4. Output layer is layer 5.
|
|||
|
|
* Each column of neurons in the vertical plane typically respond to the same part of the visual field and the same orientation.
|
|||
|
|
* Neurons in the horizontal plane respond to neighboring areas of the visual field and change orientation preferences that repeats each milimeter or so.
|
|||
|
|
* Neurons in layer 4 respond to just one eye or the other (monocular cells) but other layers have neurons that can respond from either eye. This sets up ocular dominance columns in the cortex.
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
Now let’s go over the structural and functional organization of visual neocortex
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Anatomical organization of visual cortex
|
|||
|
|
|
|||
|
|
Neuroscience 5e Fig. 12.10
|
|||
|
|
|
|||
|
|
<div><img src="tmp/Neuroscience5e-Fig-12.10-0_d67378b.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Neurons in the primary visual cortex respond selectively to oriented edges
|
|||
|
|
|
|||
|
|
* David Hubel and Torsten Wiesel— measured responses of neurons in visual cortex. Found not center-surround like RGCs and LGN neurons but found that they respond to bars or lines but only of a particular orientation.
|
|||
|
|
* Two types of cells: Simple, respond to stimulus only if matches orientation. Spots of light don’t do much, bars or lines make them fire. They also have surround inhibition. Receptive fields can be generated by having 3-4 LGN neurons innervate one simple cell.
|
|||
|
|
* Complex cells- bigger receptive fields, not strongly orientation selective, no clear on or off zones, detect movement.
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Neurons in the primary visual cortex respond selectively to oriented edges
|
|||
|
|
|
|||
|
|
Neuroscience 5e Fig. 12.8
|
|||
|
|
|
|||
|
|
<div><img src="tmp/Neuroscience5e-Fig-12.08-1R_b5c538e.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Neurons in the primary visual cortex respond selectively to oriented edges
|
|||
|
|
|
|||
|
|
Neuroscience 5e Fig. 12.8
|
|||
|
|
|
|||
|
|
<div><img src="tmp/Neuroscience5e-Fig-12.08-2R_dfdfd60.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
<div><img src="tmp/Neuroscience5e-Fig-12.08-3R_76c8b31.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Neurons in the primary visual cortex respond selectively to oriented edges
|
|||
|
|
|
|||
|
|
Neuroscience 5e Fig. 12.9
|
|||
|
|
|
|||
|
|
<div><img src="tmp/Neuroscience5e-Fig-12.09-0_26235aa.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
Natural scenes consist of a spectrum of high contrast, oriented edges.
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Information from multiple LGN inputs are used to make cortical neuron receptive fields
|
|||
|
|
|
|||
|
|
* Filtering of info from multiple LGN cells is used to make simple and complex cells in visual cortex
|
|||
|
|
|
|||
|
|
red dots inhibitory synapses
|
|||
|
|
|
|||
|
|
[LGN on cell: http://www.youtube.com/watch?v=jIevCFZixIg](http://www.youtube.com/watch?v=jIevCFZixIg)
|
|||
|
|
|
|||
|
|
[V1 simple cell: http://www.youtube.com/watch?v=Cw5PKV9Rj3o](http://www.youtube.com/watch?v=Cw5PKV9Rj3o)
|
|||
|
|
|
|||
|
|
[Hubel: https://www.youtube.com/watch?v=y_l4kQ5wjiw](https://www.youtube.com/watch?v=y_l4kQ5wjiw)
|
|||
|
|
|
|||
|
|
<div><img src="tmp/image5_3ab5bfc.png" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
other hubel vid I saw and marked times…
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
* david hubel 1:24-2:18:
|
|||
|
|
* 125 million rods and cones in each eye.
|
|||
|
|
* misha pavel, sobel filter
|
|||
|
|
* try to build a robot to see and interpret images and it's hard.
|
|||
|
|
|
|||
|
|
: 4:45 nice example of movement and perception of cat face
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Types of simple cell receptive fields
|
|||
|
|
|
|||
|
|
<div><img src="tmp/image6_8eafbb8.png" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Some cells are selective for the direction of movement
|
|||
|
|
|
|||
|
|
We use multiple types of visual information for perception:
|
|||
|
|
|
|||
|
|
[https://www.youtube.com/watch?v=y_l4kQ5wjiw](https://www.youtube.com/watch?v=y_l4kQ5wjiw)
|
|||
|
|
|
|||
|
|
<div><img src="tmp/image7_50fb6ef.png" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
others selective for movement, disparity
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
* david hubel 1:24-2:18:
|
|||
|
|
* 125 million rods and cones in each eye.
|
|||
|
|
* misha pavel, sobel filter
|
|||
|
|
* try to build a robot to see and interpret images and it's hard.
|
|||
|
|
|
|||
|
|
: 4:45 nice example of movement and perception of cat face
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Figure 12.11 The basis of functional maps in primary visual cortex
|
|||
|
|
|
|||
|
|
The basis of functional maps in visual cortex
|
|||
|
|
|
|||
|
|
Neuroscience 5e Fig. 12.11
|
|||
|
|
|
|||
|
|
<div><img src="tmp/Neuroscience5e-Fig-12.11-0_1e2c764.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Mapping receptive fields in the living brain
|
|||
|
|
|
|||
|
|
* Illuminator adds red light to help measure oxy-deoxy hemoglobin levels (a sign of increased neural activity).
|
|||
|
|
* Show monkey monitor that contains a given orientation of a line. Tell computer to color-code areas that respond to a certain orientation.
|
|||
|
|
* Repeat for all such orientations, get a pinwheel affect.
|
|||
|
|
|
|||
|
|
<div><img src="tmp/image1_4d7444e.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
data display, surface of brain
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Repeating units of orientation columns in visual cortex
|
|||
|
|
|
|||
|
|
<div><img src="tmp/image8_18631c1.png" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Mixing of pathways from the two eyes first occurs in the visual cortex
|
|||
|
|
|
|||
|
|
Fig. Neuroscience (c) 2001 Sinauer Associates, Inc.
|
|||
|
|
|
|||
|
|
<div><img src="tmp/PN12100_25f9734.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Ocular dominance bands in layer 4 of primary visual cortex (V1, area 17)
|
|||
|
|
|
|||
|
|
Hubel, Wiesel, and Levay 1976
|
|||
|
|
|
|||
|
|
<div><img src="tmp/image9_ce84487.png" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
If we were to peer at layer 4 only and perform a histological procedure that labels thalamocortical inputs from only one eye we would see a pattern like this in primate cortex, resembling ocular dominance bands or stripes.
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Columnar organization of ocular dominance
|
|||
|
|
|
|||
|
|
<div><img src="tmp/PN12132_f1003e0.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
<div><img src="tmp/PN12131_f44cd94.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## The Nobel Prize in Physiology or Medicine (1981)
|
|||
|
|
|
|||
|
|
“for their discoveries concerning information processing in the visual system”
|
|||
|
|
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David H. Hubel
|
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Torsten N. Wiesel
|
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<div><img src="tmp/medicine_9006bea.jpg" height="100px"><figcaption></figcaption></div>
|
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<div><img src="tmp/hubel_postcard_bf39419.jpg" height="100px"><figcaption></figcaption></div>
|
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<div><img src="tmp/wiesel_postcard_f6eea8d.jpg" height="100px"><figcaption></figcaption></div>
|
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Note:
|
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|
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|
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|
|
---
|
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|
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## Maps in the visual system- ocular dominance columns and orientation selectivity in visual cortex
|
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Ocular
|
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|
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dominance
|
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Orientation
|
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|
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|
|
selectivity
|
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|
<div><img src="tmp/kandelschwartz-fig27-17_3d15d30.pdf" height="100px"><figcaption></figcaption></div>
|
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|
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|
|
<div><img src="tmp/kandelschwartz-fig27-14_e52cde6.pdf" height="100px"><figcaption></figcaption></div>
|
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|
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Note:
|
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|
|||
|
|
The organization of connections from each eye is shown here where if we were to look at a chunk of primary visual cortex from ferrets, cats, or monkeys we would find ocular dominance columns where the response properties of neighboring cells is dominated by that of one eye or the other and which can be demonstrated by electrophysiological recordings or by histological staining for cytochrome oxidase.
|
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|
|
Overlaid on this map of alternating ocular dominance columns is a map of orientation pinwheels in visual cortex shown by the isocontour lines on the surface *here* and by the colored orientation map *here* -->where the colored map represents the preferred response of neighboring neurons to high contrast edges presented at different orientations in the visual field.
|
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|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Parallel processing in the visual system
|
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|
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|
|
* Separate pathways for color and movement.
|
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|
|
* In human retina there are three main types of retinal ganglion cells, called M, P , and K types. M and P types best characterized.
|
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|
|
* M cells are bigger, have larger receptive fields, faster conduction velocities, and respond transiently to visual stimulation. P cells smaller, respond in a sustained fashion.
|
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|
|
* P cells respond to color. This is because their center and surround are from different cones.
|
|||
|
|
* M cells do not respond well to color because center and surround are from the same type of cones.
|
|||
|
|
* M, P, and K RGCs go to different layers in the LGN which in turn project to different layers in V1.
|
|||
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|
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|
Note:
|
|||
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|
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|
|||
|
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|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## P type RGCs are sensitive to color contrast
|
|||
|
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|
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|
|
<div><img src="tmp/image10_9804c4d.png" height="100px"><figcaption></figcaption></div>
|
|||
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|
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|
|
Note:
|
|||
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|
|||
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|
|||
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|
|||
|
|
---
|
|||
|
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|
|||
|
|
## Magno-, parvo-, and konio-cellular streams of information in the visual system
|
|||
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|
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|
|
<div><img src="tmp/Neuroscience5e-Fig-12.15-0_9a7f451.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
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|
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|
Note:
|
|||
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|
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|
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|
|||
|
|
---
|
|||
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|
|||
|
|
## Extrastriate visual areas
|
|||
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|
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|
|
* There are many other areas of the brain that process visual information, each gets info derived from primary visual cortex (V1).
|
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|
|
* Specialized for different functions.
|
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|
|
* MT middle temporal area, responds to direction of a moving edge without regard to its color.
|
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|
|
* V4, responds to color of a stimulus without regard to form.
|
|||
|
|
* 10 different visual areas, each with a topographic map.
|
|||
|
|
* Damage in these areas can really give weird experiences.
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Subdivisions of the extrastriate cortex in the macaque monkey
|
|||
|
|
|
|||
|
|
Neuroscience 5e Fig. 12.16
|
|||
|
|
|
|||
|
|
<div><img src="tmp/Neuroscience5e-Fig-12.16-1R_3bd6c35.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
<div><img src="tmp/Neuroscience5e-Fig-12.16-2R_690c891.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Localization of multiple visual areas in the human brain using fMRI
|
|||
|
|
|
|||
|
|
Neuroscience 5e Fig. 12.17
|
|||
|
|
|
|||
|
|
<div><img src="tmp/PN12161_67aa406.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Organization of the dorsal and ventral visual pathways
|
|||
|
|
|
|||
|
|
Dorsal stream: object location (Where?)
|
|||
|
|
|
|||
|
|
* Knowing location of objects in space. Linking visual data with movement/action
|
|||
|
|
|
|||
|
|
Ventral stream: object recognition. (What?)
|
|||
|
|
|
|||
|
|
* Color: V4 (temporal-parietal junction).
|
|||
|
|
* Face recognition: fusiform gyrus
|
|||
|
|
|
|||
|
|
Neuroscience 5e Fig. 12.18
|
|||
|
|
|
|||
|
|
<div><img src="tmp/PN12170_ea4f6df.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Hierarchical visual processing
|
|||
|
|
|
|||
|
|
<div><img src="tmp/2015-11-0217.09.28_crop_c74cd58.jpg" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
“the brain is a complex of widely and reciprocally interconnected systems and that the dynamic interplay of neural activity within and between systems is the very essence of brain function”. And indeed if you look at this—> anatomical wiring diagram for different visual areas represented by different colors you will notice that we use an organized constellation of brain regions to process and route different types of visual information
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Subdivisions of the extrastriate cortex in the macaque monkey
|
|||
|
|
|
|||
|
|
Van Essen 1992
|
|||
|
|
|
|||
|
|
<div><img src="tmp/ScreenShot2015-09-13at12.34.35PM_8ea399c.png" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
<div><img src="tmp/ScreenShot2015-09-13at12.33.31PM_63619a9.png" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
but he also emphasized that “the brain is a complex of widely and reciprocally interconnected systems and that the dynamic interplay of neural activity within and between systems is the very essence of brain function”. And indeed if you look at this—> anatomical wiring diagram for different visual areas represented by different colors you will notice that we use an organized constellation of brain regions to process and route different types of visual information and each one of these brain regions consists of many thousands of these basic cortical column building blocks described on the previous slide.
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Face recognition cells in the fusiform gyrus
|
|||
|
|
|
|||
|
|
<div><img src="tmp/image11_1f4523f.png" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
responses of a monkey’s neuron in their homologous area to fusiform gyrus to various facelike or non facelike stimuli.
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
color synesthesia: association of colors with certain numbers, letters, or objects
|
|||
|
|
|
|||
|
|
prosopagnosia: face blindness. Our patient Dr. P from earlier?
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Grandmother neurons in the human brain?
|
|||
|
|
|
|||
|
|
[http://www.youtube.com/watch?v=Y7BZlDfVR6k](http://www.youtube.com/watch?v=Y7BZlDfVR6k)
|
|||
|
|
|
|||
|
|
Quiroga et al., Nature 2005
|
|||
|
|
|
|||
|
|
<div><img src="tmp/ScreenShot2015-11-02at12.57.02PM_d992132.png" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
Invariant visual representation by single neurons in the human brain. Quiroga et al., Nature 2005
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
Recordings were made in medial temporal lobe of the cerebral cortex including entorhinal cortex and hippocampus course of clinical procedures to treat epilepsy.
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
Interestingly this cell did not respond to pictures of Jennifer Aniston with Brad Pitt, maybe this cell had ‘moved on’ just like Miss Aniston. But other cells in this work did respond to selectively to Aniston with her friend’s costar Lisa Kudrow.
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
One object per neuron?
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
however these results may be best understood in a non-visual context. Some of the example cells responded not only to pictures but also to the printed name of a particular person or object. So this type of invariance must be based off learned associations.
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Grandmother neurons: a sparse neural code
|
|||
|
|
|
|||
|
|
C. Connor, Nature 2005
|
|||
|
|
|
|||
|
|
<div><img src="tmp/ScreenShot2015-11-03at9.53.42AM_c595899.png" height="100px"><figcaption></figcaption></div>
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
invariant visual representation by single neurons in the human brain. Quiroga et al., Nature 2005
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
Connor Nature 2005, N&V on Quiroga et al:
|
|||
|
|
|
|||
|
|
>a more technical term for the grandmother issue is ‘sparseness’.
|
|||
|
|
|
|||
|
|
>At earlier stages in the object recognition pathway the neural code for an object is a broad activity pattern distributed across a population of neurons, each responsive to a discrete visual feature. At later, higher order processing stages, neurons become increasingly responsive for combinations of features and the code becomes increasingly sparse.
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
sparse and non-variant
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Weird visual defects
|
|||
|
|
|
|||
|
|
* Cerebral achromatopsia
|
|||
|
|
* Do not see in color-only black and white. Legions in extrastriate cortex regions like V4 or in ventral stream.
|
|||
|
|
* Lesions in MT regions cause people to have defects in detecting motion (Hard to pour drinks accurately, see moving cars, etc).
|
|||
|
|
* Blind sight
|
|||
|
|
* Disruptions in V1 cause blindness.
|
|||
|
|
* However some people can “guess” what an object is. Implies that there are other projections from eye to brain (superior colliculus) that can somehow compensate for loss of V1.
|
|||
|
|
|
|||
|
|
Note:
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|