The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1...
-
Upload
scot-garrett -
Category
Documents
-
view
215 -
download
0
Transcript of The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1...
![Page 1: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/1.jpg)
The Visual systemThe Visual systemor Chapter 20 of Fundamental Neuroscienceor Chapter 20 of Fundamental Neuroscience
Genevieve Legault
AHD
Wednesday April 1st 2008
![Page 2: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/2.jpg)
Plan of presentationPlan of presentation
• Brief overview of eye anatomy • Retina anatomy• Different photoreceptors• Transduction of signal• Retinal cells• Visual pathway• Visual cortex and its organization• Summary
![Page 3: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/3.jpg)
Objectives of presentationObjectives of presentation
• Understand the mechanism of photoreceptors
• Recognize the differences between rods and cones
• Know the visual pathway, and their associated VF defects if interrupted
• Learn the organization of the visual cortex
![Page 4: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/4.jpg)
Brief overview of eye anatomy:Brief overview of eye anatomy:
Anatomy quizz → GUESS WHO ….
![Page 5: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/5.jpg)
Anatomy quizzAnatomy quizz
• I’m a transparent protective coating for the optic structures.
![Page 6: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/6.jpg)
Brief overview of eye anatomyBrief overview of eye anatomy
![Page 7: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/7.jpg)
Anatomy quizzAnatomy quizz
• I’m a transparent protective coating for the optic structures.
• Its lateral margin are continuous with which structure?
• Conjunctiva!
![Page 8: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/8.jpg)
Anatomy quizzAnatomy quizz
• Circumferentially organized muscle
![Page 9: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/9.jpg)
Brief overview of eye anatomyBrief overview of eye anatomy
![Page 10: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/10.jpg)
Anatomy quizzAnatomy quizz
• Iris sphincter is paraΣ:– Begins with
preganglionic neurons with cell bodies in EW nucleus
– Axons end in the ciliary ganglion
– Postganglionic end as neuromuscular synapse (ACh)
![Page 11: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/11.jpg)
Anatomy quizzAnatomy quizz
• Iris sphincter is paraΣ:– Begins with
preganglionic neurons with cell bodies in EW nucleus
– Axons end in the ciliary ganglion
– Postganglionic end as neuromuscular synapse (ACh)
![Page 12: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/12.jpg)
Anatomy quizzAnatomy quizz
• Epithelium covering which structure produces the fluid filling the anterior chamber?
![Page 13: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/13.jpg)
Brief overview of eye anatomyBrief overview of eye anatomy
![Page 14: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/14.jpg)
Anatomy quizzAnatomy quizz
• Epithelium covering which structure produces the fluid filling the anterior chamber?
• This fluid then drains into me.
![Page 15: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/15.jpg)
Brief overview of eye anatomyBrief overview of eye anatomy
![Page 16: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/16.jpg)
Anatomy quizzAnatomy quizz
• Epithelium covering which structure produces the fluid filling the anterior chamber?
• This fluid then drains into me.
• If the outflow is obstructed, we then get me.
![Page 17: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/17.jpg)
Glaucoma capsuleGlaucoma capsule
• Damage from the periphery toward the center
• ~ 90% open-angle or normal angle– Idiopathic ↑ in pressure
• ~ 5% angle abnormally acute (closed-angle)– Obstruction of normal flow of fluid
• Remaining: canals blocked by debris (infection, DM, hemorrhage into anterior chamber)
![Page 18: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/18.jpg)
Glaucoma: which one is true?Glaucoma: which one is true?
• Vision is typically:– 1) blurred and dimmed– 2) not blurred but dimmed– 3) blurred but not dimmed– 4) normal
![Page 19: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/19.jpg)
Anatomy quizzAnatomy quizz
• Radially arranged muscle
![Page 20: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/20.jpg)
Brief overview of eye anatomyBrief overview of eye anatomy
![Page 21: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/21.jpg)
Anatomy quizzAnatomy quizz
• Iris dilator is Σ:– Preganglionic begins in the intermediolateral
cell column of the spinal cord, in the upper thoracic region
– Axons end in superior cervical ganglion– Postganglionic end in neuromuscular synapse
(NE)
![Page 22: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/22.jpg)
Iris is smart!Iris is smart!
• With light, ACh is released on both muscarinic sphincter muscles (contraction) and dilator muscles (presynaptic inhibition of NE release, therefore blocking dilator contraction)
![Page 23: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/23.jpg)
Anatomy quizzAnatomy quizz
• Uvea is formed by which 3 structures?
![Page 24: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/24.jpg)
Anatomy quizzAnatomy quizz
• Uvea is formed by which 3 structures?– Iris– Ciliary body– Choroid
• Highly vascularized
• Pigmented tissue layer between retina and sclera
![Page 25: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/25.jpg)
Brief overview of eye anatomyBrief overview of eye anatomy
![Page 26: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/26.jpg)
Retina = neural retina + Retina = neural retina + retinal retinal pigment epitheliumpigment epithelium
→ Continuous sheet of cuboidal cells bound by tight junctions
Functions:-nutrition supply-protection of photoreceptors-phagocytosis
![Page 27: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/27.jpg)
Neural retina = photoreceptors and Neural retina = photoreceptors and associated neuronsassociated neurons
• Photoreceptors absorb quanta of light (photons) and convert it into electrical signal
• Ganglion cells send axons as the optic nerve
![Page 28: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/28.jpg)
7 layers of neural retina7 layers of neural retina
• **** Pathway of light and neural outflow are inverted
****
![Page 29: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/29.jpg)
Blood supplyBlood supply
• Internal carotid artery↓
ophthalmic artery → Posterior ciliary artery→Central retinal artery - external portion
-inner retina of the optic nerve (neural retina) - choroidal -pial arteries to circulation optic nerve -outer retina
![Page 30: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/30.jpg)
PhotoreceptorsPhotoreceptors
• Detection and transduction of light in outer segment pointing toward the pigment epithelium
• Narrow stalk (cilium) connects to the inner segment (containing mitochondria)
• Then outer plexiform layer where synapse
![Page 31: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/31.jpg)
Pathway of light - CiliumPathway of light - Cilium
![Page 32: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/32.jpg)
2 types of photoreceptors2 types of photoreceptors
• Rods • Cones
![Page 33: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/33.jpg)
TransductionTransduction
• Conformational change
• ↓cGMP• Closing Na+
current• Hyperpolariz
ation• Passive
propagation
![Page 34: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/34.jpg)
TransductionTransduction
• Photoreceptors are the only sensory neurons that hyperpolarize in response to the relevant stimulus
![Page 35: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/35.jpg)
TransductionTransduction
• At rest:– ↑ cGMP level
– ↑ Na+ current
– Resting potential -40 mV
– Constant glutamate release
• Light:– ↓ cGMP level
– Blocks Na+ current
– Hyperpolarize: -60 mV
– ↓ in tonic glutamate release
![Page 36: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/36.jpg)
ConesCones
• 3 types, each tuned to a different wavelength– L-cones = long wavelengths (red cones)– M-cones = medium wavelengths (green cones)– S-cones = short wavelengths (blue cones)
• Each color = unique combination
![Page 37: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/37.jpg)
Color confusionColor confusion
• Genetic defect in one of the opsin (one type of cone)– L and M opsins are located on Chromo X,
therefore more frequent in ♂
– Inability to perceive red = protanopia– Inability to perceive green = deuteranopia
![Page 38: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/38.jpg)
FoveaFovea• Light reaches the
macula
• Center = fovea
![Page 39: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/39.jpg)
FoveaFovea• Light reaches the
macula• Center = fovea• Thinner inner retina,
to allow max of light (outer nuclear and photoreceptor outer segment only in the center)
• Only cones
![Page 40: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/40.jpg)
Receptive fieldsReceptive fields
• Definition:– Sum of the areas in which the stimulus affects
the activity of that neuron
• Roughly circular– Center – Doughnut-shaped outer rim with usually the
opposite response
![Page 41: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/41.jpg)
Retinal synapsesRetinal synapses
• Only ganglion cells have voltage-gated Na+ channels therefore only one using action potentials
• Other cells use graded potentials
![Page 42: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/42.jpg)
Retinal synapsesRetinal synapses
• Outer plexiform layer– One photoreceptor– 1 centrally placed bipolar cell triad– 2 laterally placed horizontal cells
• Inner plexiform layer– Bipolar cells with on or off ganglion cells– Amacrine cells with ganglion cells, other
amacrine cells, and bipolar cells
![Page 43: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/43.jpg)
Horizontal cellsHorizontal cells• Course parallel to the retina
• Glutaminergic input from photoreceptor
• GABAergic output to adjacent photoreceptors → inhibiting surround to sharpen receptive field
![Page 44: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/44.jpg)
Bipolar cellsBipolar cells
• Between photoreceptor cells and ganglion cells
• 1st cells to exhibit the center-surround receptive field organization
• 2 types– On: depolarizing, sign-inverting– Off: hyperpolarizing, sign-conserving
![Page 45: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/45.jpg)
Bipolar cellsBipolar cells
![Page 46: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/46.jpg)
Amacrine cellsAmacrine cells
• May contain different neurotransmitters
• Sense change in change (variation in speed)
![Page 47: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/47.jpg)
Ganglion cellsGanglion cells
• Output cells of the retina: axons converge on the optic disc to form the optic nerve
• Also have center-surround receptive fields (like bipolar cells)
![Page 48: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/48.jpg)
Ganglion cells: different typesGanglion cells: different types
• Alpha
• Largest
• Periphery (input mainly from rods)
• Y cells
• Participate little in color, larger receptive field
• M cells = magnocellular layers in LGN
• Beta
• Medium-sized
• Central retina (input mainly from cones)
• X cells
• Color, small receptive fields
• P cells = parvocellular layers in LGN
![Page 49: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/49.jpg)
Ganglion cells: different typesGanglion cells: different types
• Other types: gamma, delta, epsilon
• W cells
• Smaller cell bodies
• Variety of receptive field sizes and physiologic responses
![Page 50: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/50.jpg)
Retinal projectionsRetinal projections
![Page 51: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/51.jpg)
Retinal projectionsRetinal projections
Retinogeniculate projections
![Page 52: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/52.jpg)
Optic disc and nerveOptic disc and nerve
• No photoreceptors in the optic disc (only ganglion cell axons): blind spot
• Whereas greatest visual acuity is at the fovea
• Subarachnoid space extends along the ON: ↑ICP can block axoplasmic flow and lead to stasis and papilledema
![Page 53: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/53.jpg)
Lateral Geniculate NucleusLateral Geniculate Nucleus
• Layers 1 to 6, ventral to dorsal
• 1 and 2: M type– Rapid– Larger field– Sensitive to
moving stimuli• 3-6: P type
– Slower– Smaller field– Tonic response to stationnary stimuli
Temporal retina (Nasal VF): layers 2,3 and 5
Nasal retina (Temporal VF): layers 1,4 and 6
![Page 54: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/54.jpg)
Optic radiationsOptic radiations
• Geniculostriate or geniculocalcarine pathway
Through retrolenticular limb of internal capsule
Lingual gyrus
Cuneus
![Page 55: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/55.jpg)
Blood supplyBlood supply
Anteromedial branches of Acom and A1Branches of
ophthalmic artery
Ant choroidal artery
Thalamogeniculate artery, branch of PCA
Branches of MCA and PCA
![Page 56: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/56.jpg)
Primary visual cortexPrimary visual cortex
• Striate cortex, area 17
• Cortex with wide layer IV, with an extra band of myelinated fibers: stria of Gennari, which give its name to the cortex
• Macular sparing: collateral of MCA to caudal parts of visual cortex
![Page 57: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/57.jpg)
Cortical Cortical neuronsneurons
• Concentric, as retinal ganglion cells and LGN cells
• Elongated receptive fields:– Simple: anywhere, but max when entirely fills– Complex: sensitive to position and angle– Hypercomplex: also sensitive to lenght of
stimulus (if extends into inhibitory zone, will ↓ the response)
![Page 58: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/58.jpg)
Columnar organizationColumnar organization
• Orientation columns– Perpendicular to surface:
• Random # of simple, complex, hypercomplex
• same optimal stimulus orientation
• Ocular dominance columns– Stronger response when stimulus from one eye
– Adjacent ocular dominant column: other eye
– 1 ipsi + 1 contralat = hypercolumn
– Critical to stereopsis (depth perception): requires proper stimulation from both eyes
![Page 59: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/59.jpg)
Columnar organizationColumnar organization
![Page 60: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/60.jpg)
Other visual cortical areasOther visual cortical areas
![Page 61: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/61.jpg)
In briefIn brief
• Ganglion cells are the ouput cells of the retina• Damage to optic radiations may result in
homonymous quadrantanopia• Lesions in the visual cortex may result in macular
sparing• Interruption of visual input from 1 eye during
critical period may result in loss of stereopsis• Lesions of association cortices result in various
types of agnosia
![Page 62: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/62.jpg)
Take Home MessagesTake Home Messages
• 2 types of photoreceptors
![Page 63: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/63.jpg)
2 types of photoreceptors2 types of photoreceptors
![Page 64: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/64.jpg)
2 types of photoreceptors2 types of photoreceptors
• Rods– Rhodopsin
– Smallerspherule
– More in periphery
• Cones– Opsin
– Largerpedicle
– More central
![Page 65: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/65.jpg)
Take Home MessagesTake Home Messages
• 2 types of photoreceptors
• 2 types of ganglion cells
![Page 66: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/66.jpg)
Ganglion cells: different typesGanglion cells: different types
• Alpha
• Largest
• Periphery (input mainly from rods)
• Y cells
• Participate little in color, larger receptive field
• M cells = magnocellular layers in LGN (layers 1 and 2): localization
• Beta
• Medium-sized
• Central retina (input mainly from cones)
• X cells
• Color, small receptive fields
• P cells = parvocellular layers in LGN (layers 3 through 6): recognition
![Page 67: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/67.jpg)
Take Home MessagesTake Home Messages
• 2 types of photoreceptors
• 2 types of ganglion cells
• Lesions at different places in visual pathway produce typical VF defects: know your anatomy!!
![Page 68: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/68.jpg)
Visual PathwayVisual Pathway
![Page 69: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/69.jpg)
![Page 70: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/70.jpg)
Take Home MessagesTake Home Messages
• 2 types of photoreceptors
• 2 types of ganglion cells
• Lesions at different places in visual pathway produce typical VF defects
• Fovea has stronger VA, therefore thinner inner retinal layers
![Page 71: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/71.jpg)
FoveaFovea
![Page 72: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/72.jpg)
Take Home MessagesTake Home Messages
• 2 types of photoreceptors
• 2 types of ganglion cells
• Lesions at different places in visual pathway produce typical VF defects
• Fovea has stronger VA, therefore thinner inner retinal layers– mainly cones
![Page 73: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/73.jpg)
Fovea againFovea again
![Page 74: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/74.jpg)
Take Home MessagesTake Home Messages
• Photoreceptors are the only sensory neurons that hyperpolarizein response to the relevant stimulus
• Which cell(s) can detect speed change?
![Page 75: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/75.jpg)
Take Home MessagesTake Home Messages
• Photoreceptors are the only sensory neurons that hyperpolarizein response to the relevant stimulus
• Which cell(s) can detect speed change?– Amacrine cells
![Page 76: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/76.jpg)
Take Home MessagesTake Home Messages
• Photoreceptors are the only sensory neurons that hyperpolarizein response to the relevant stimulus
• Which cell(s) can detect speed change?– Amacrine cells
• Which retinal cell(s) have center-surround receptive field?
![Page 77: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/77.jpg)
Take Home MessagesTake Home Messages
• Photoreceptors are the only sensory neurons that hyperpolarizein response to the relevant stimulus
• Which cell(s) can detect speed change?– Amacrine cells
• Which retinal cell(s) have center-surround receptive field?– Bipolar and ganglion cells
![Page 78: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/78.jpg)
Take Home MessagesTake Home Messages
• Primary visual cortex have – Orientation columns– Ocular dominance columns
![Page 79: The Visual system or Chapter 20 of Fundamental Neuroscience Genevieve Legault AHD Wednesday April 1 st 2008.](https://reader038.fdocuments.in/reader038/viewer/2022110321/56649cf15503460f949c0b0f/html5/thumbnails/79.jpg)
THANK YOU!THANK YOU!
QUESTIONS???