lecture 13

lecture 13 - Saturday, November 6, 2010 CENTER-SURROUND How...

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Unformatted text preview: Saturday, November 6, 2010 CENTER-SURROUND How does this work???? Circuit • Two bipolar cells synapse with cone, an on center and off center • On center bipolars are normally inhibited by glutamate, less glutamate, less inhibition, more release of neurotransmitter, and increase of on-center RGC firing. • Off center bipolars are normally activated by glutamate, become depolarized, increase transmitter release and decrease firing rate of Off-center RGC Saturday, November 6, 2010 CENTER-SURROUND How does this work???? On Signal • Light hits cone → hyperpolarization → decrease glutamate release • On Bipolar gets less glutamate → depolarized → increase in glutamate release • On RGC gets more glutamate → depolarized Saturday, November 6, 2010 CENTER-SURROUND How does this work???? • Light hits cone → hyperpolarization → decrease glutamate release • Off Bipolar gets less glutamate → hyperpolarized → decrease in glutamate release • Off RGC gets less glutamate → not depolarized Off Signal Saturday, November 6, 2010 CENTER-SURROUND How does this work???? The Surround • When surround is illuminated, cones hyperpolarize → decrease glutamate release • Less glutamate → hyperpolarized horizontal cell → decrease GABA release • Less GABA → depolarize photoreceptors, including center → INcrease glutamate • MORE photoreceptor glutamate release → less on-center RGC firing Saturday, November 6, 2010 VISION: CENTRAL VISUAL PATHWAYS Jason Triplett, PhD Saturday, November 6, 2010 GOALS •Anatomy of visual projection pathways •Topographical representation of visual field •Columnar organization of visual cortex •Receptive field types in cortex Saturday, November 6, 2010 RETINOFUGAL PROJECTIONS All visual information is carried to the brain by RGCs, which target different brain structures and carry different information • • • • • SC - head/eye orientation pretectum - pupillary reflexes dLGN - image processing & relay vLGN - luminance information SCN - circadian rhythms • >20 targets total Saturday, November 6, 2010 HUMAN VISUAL SYSTEM Saturday, November 6, 2010 • Dorsal Lateral Geniculate Nucleus (dLGN) • located in the thalamus • receives visual info from retina, relays to cortex • most important retinal projection for visual perception • Pretectum • located at midbrain/thalamus boundary • responsible for pupillary light reflex • Superior Colliculus (SC) • located in midbrain • integrates visual information from retina and cortex • coordinates head & eye movements • Suprachiasmatic nucleus • located in midbrain • involved in day/night cycles Saturday, November 6, 2010 RETINAL TARGETS OTHER TERMS • Optic Disk • Site where all RGCs exit the retina • Optic nerve (cranial nerve II) • Bundle of myelinated RGC axons projecting to the brain • Optic Chiasm • Site where optic nerve enters the brain • nasal axons cross, temporal axons don’t • Optic Radiation • part of the internal capsule (connects cortex and thalamus) • Primary Visual Cortex (V1), Area 17, Striate Cortex • First site of cortical visual processing Saturday, November 6, 2010 PARALLEL PROCESSING RGC subtypes (remember different receptive fields) carry distinct bits of data to different nuclei Example: Melanopsin Ganglion cells project to SCN, control circadian clock The Journal of Comparative Neurology. DOI 10.1002/cne The Journal of Comparative Neurology. D 334 S. HA PROJECTIONS OF MELANOPSIN GANGLION CELLS 329 SCN Melanopsin+ RGCs Melanopsin RGC Ablation Fig. 1. X-gal labeling of melanopsin ganglion cells in a retinal wholemount. Composite image derived from a stack of brightfield photomicrographs locally masked to reveal all labeled processes in sharp focus. Arrowheads mark axons in the optic fiber layer. Inset: Schematic charting of distribution of X-gallabeled cell bodies in one retinal wholemount. Scale bar 50 m. Fig. 2. Distribution of axons of mRGCs in optic nerve and tract. A: Confocal image of axonal anti- -galactosidase immunoreactivity in a transverse section of the optic nerve. B,C: X-gal staining of axons in the optic tract contralateral (B) and ipsilateral (C) to a monocular enucleation. Axonal degeneration is almost complete in B but nearly absent in C, indicating that, beyond the SCN, melanopsin RGCs have predominantly crossed projections. Scale bar 100 m in A; 200 m in C (applies to B,C). (Abrahamson and Moore, 2001). Such immunostaining is abolished by preadsorption with VIP but not with various other neuropeptides (manufacturer’s technical information). A few retinas were immunostained for -galactosidase. Retinas were postfixed overnight in 4% paraformaldehyde (in PBS) at 4°C. Immunohistochemical protocols followed those used for the brain sections except that the anti- galactosidase primary antibody (Cortex #CR7001RP5) was used at 1:1,000 dilution and the secondary antibody was tagged with Alexa Fluor 488, used at 1:250 dilution, overnight at 4°C. Saturday, November 6, 2010 PUPILLARY REFLEX RGCs that project to the pretectum carry luminance info, used to control pupillary response to light • Light hits retina, retinopretectal ganglion cells project to both sides of the brain • Pretectal neurons project to contra- and ipsilateral Edinger-Westphal nuclei (midbrain) • Edinger-Westphal projects to the ipsilateral ciliary ganglion • Ciliary ganglion projects to iris constrictor muscles • Shining light in one eye causes both pupils to constrict Saturday, November 6, 2010 PUPILLARY REFLEX Circuitry diagram http://library.med.utah.edu/kw/animations/hyperbrain/parasymp_reflex/reflex.html Saturday, November 6, 2010 IMAGE FORMING PROJECTIONS The spatial order of RGCs in the retina are maintained in target regions. Termed topographic mapping, retinotopy • The visual field is projected onto the retina upside down and backwards • Can be divided into superior/inferior & left/right halves • Left visual field processed in right brain, right in left • Humans are binocular, meaning both eyes see parts of both left and right visual field - therefore part of the retina projects contralateral and part ipsilateral Saturday, November 6, 2010 SUPERIOR COLLICULUS Projection to SC/tectum used for reflexive actions. In frog, used to initiate tongue lash to catch flies. otation experiment in which the optic tract is severed and the eyes rotated by 1808. (a) In the normal retina, dorsal axons project to Saturday, November 6, 2010 ntral axons project to lateral sites. After rotation of the retina and regeneration of the axonal pathways, the map remains topographic IMAGE ON RETINA Superior Inferior Saturday, November 6, 2010 IMAGE ON RETINA Saturday, November 6, 2010 IMAGE ON RETINA • There is overlap in visual fields, most objects seen by both eyes. • Objects in the left visual field are seen by the nasal retina of the left eye and the temporal retina of the right eye. • Objects on extreme periphery are seen only by the nasal retina on that side. • Nasal RGC axons cross the midline at the optic chiasm (contra lateral) and temporal RGC axons do not cross at the chiasm (ipsilateral). • 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. • 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. Saturday, November 6, 2010 IMAGE ON RETINA Saturday, November 6, 2010 TOPOGRAPHY In forward-looking animals, the visual image is split In animals with eyes on the side of the head, entire projection crosses over. Saturday, November 6, 2010 TOPOGRAPHY • Spatial relationships of retinal ganglion cells Neuron are maintained in the target area • i.e. the representation of the visual field is maintained between areas Review A term no in sic g che spe labe was and spe Saturday, November 6, 2010 TOPOGRAPHY “Lesion” experiments helped to understand topographic organization of visual field. that his discoveries w ere made a t such c ost in h uman misery. M any o f I nouye's p atients d ied a f ew m onths o r years a fter t hey w ere s hot - usually f rom c omplications associated w ith t heir brain injuries. I nouye in his i ntroduction recognizes t he h uman c ost t hat w as associated w ith these injuries. He p ut f orward t he m odest h ope t hat his w ork m ight help t o call a ttention t o t hose t ragedies and t hus help t o p ut an end t o w ar. Acknowledgements Saturday, careful analysis o f field defects in British soldiers injured in t he First W orld W ar established t he v alidity of I nouye's conclusion o n t he l ocation o f t he macular o r central visual fields in t he caudal p art o f t he human o ccipital lobe. O ne major d ifference b etween Holmes' map and t hat o f I nouye is t hat I nouye s howed t he field r epresentation e xtending 5 ° i nto t he ipsilateral visual field, in o rder t o a ccount f or t he macular sparing t hat he o bserved in cases o f unilateral injury. November 6, 2010 Holmes argued s trongly a gainst t his Tatsuji Inouye (1881-1976) Fig. 3. T atsuji I nouye a t t he age o f 48. (Kindly provided by Jiro Inouye.) We thankDavid Penn, Keepero f the Departmentsof Exhibitsand Firearms o f the ImperialWar Museumand Leslie Payne,BD5,LDS,RC5 for helpfuldiscussions on the propertieso f bulletsand their effects on tissue. We aregrateful to Tatsuji Inouye's grandsonDr Jiro Inouyeo f the Selected references 1 Gennari,F. (1782) De Peculiari Structura Cerebri Nonnulisque InouyeEyeHospital to K. B. Gardner, Ejus Morbis, Parma Ex RegioTypographeo 2 Broca,P. P. (1861) Bull. 5oc. Anat. Paris36, 330-357 (English DeputyKeepero f translation in Von Bonin,G., ed. (1960) The Cerebral Cortex, OrientalManuscripts pp. 49-72, SpringfieldThomas) and Bookso f the 3 Fritsch,G. and Hitzig, E. (1870) Arch. F. Anat. Physiol. und BritishLibrary,Masaki Wissenchaftl. IMediz. Leipzi& 300-332 (Englishtranslation in Sakuraio f the Von Bonin, G., ed. (1960) The Cerebral Cortex, pp. 73-96, Universityof Tokyo, Springfield Thomas) and Koichi5himizuo f 4 Ferrier, D. (1875) Phil. Trans. R. 5oc. 165, 433-488 5 Ferrier,D. (1876) The Functions o f the Brain (1stedn), Smith, the Departmento f Ophthalmology, Elder GunmaUniversity 6 Glickstein,M. (1985) Trends Neurosci. 8, 341-344 7 Munk, H. (1881) U berdie Funktionen tier Grosshirnrinde, A. Schoolo f Medicine, Hirschwald (English translation in Yon Bonin G., ed. (1960) for biographical The Cerebral Cortex, pp. 97-117, SpringfieldThomas) detailso f the life of 8 Henschen, S. E. (1890) Klinische u nd anatomische Beitra&e TatsujiInouye. We z ur Patholo&ie des Gehirns (Pt 1), Almquist and Wiksell thank SusanGove, 9 Inouye,T. (1909) Die SehstGrunsen bei 5chussverletzun&en t ier kortikalen 5ehsph&re nach Beobachtun&en an Versunde- MedicalLibrarianat UniversityCollege ten t ier letzten Japanische Krie&e, W. Engelmann 10 Talbot, S. and Marshal, W. H. (1941) Am. J. Ophthalmol. London for continued help with historical (Series3) 24, 1255 11 Holmes, G. and Lister,W. T. (1916) Brain 39, 34-73 sources. • Physician in Russo-Japanese War (1905) • Examined the visual field defects of soldiers with clean bullet wounds in the cortex • Determined site of injury and areas that patients could not see A nnouncement The m ajority o f articles p ublished in T INS are solicited d irectly b y the Editor. In t he interests o f s cientific accuracy and clarity, all s ubmitted manuscripts are subjected t o a r eviewing procedure. Because o f t he d iveristy o f t opics covered in T INS w e f requently need t o g o o utside t he A dvisory Editorial Board f or advice. The Editor and t he members o f t he T INS A dvisory Editorial Board w ould like t o t ake this o pportunity t o t hank some o f those w ho have c ontributed in t his w ay t o t he magazine's c ontinuing success d uring 1 986. Those t o w hom t hanks are d ue service, Inouye had an o pportunity t o examine a number o f cases o f head injury in which Japanese soldiers had been h it by a bullet t hat had had a relatively straight course t hrough the brain. In all o f these cases he made careful plots o f visual field loss and located accurately t he sites o f entrance and exit w ounds on the skull. Inouye's goal was t o relate the locus o f brain injury t o the visual field deficit t hat it produced. In order t o determine t he actual brain lesions caused by the bullet in its path, Inouye studied t he spatial relationship between the major cortical fissures and the overlying skull. He devised an instrument which he called a cranio-coordinometer t o locate precisely in TOPOGRAPHY Fig. 1 . Fig.2. Inouye's schemafor the projectiono f the visualfieldson the stdate cortex. found three surface wounds produced by the bullet. Some o f Inouye's casualties were in a prone position w hen they were hit. The bullet entered the skull at one point, exited from a second, and then reentered the body in the upper arm o r shoulder. In such cases, the three wounds were in a straight line. Postmortem examination is needed t o confirm brain damage. A lthough most o f Inouye's determinations o f the locus o f brain injury were based on calculation o f the course o f the bullet t hrough the brain, some postmortem evidence was presented. Regretably, these cases were n ot illustrated, b ut described verbally. Aside from one case in which there was some remote damage associated w ith notes and visual field plots f or 29 cases o f brain injury. Inouye then used the data t o work out the w ay in which the visual fields are mapped on the human brain. Fig. 38 o f Inouye's monograph (Fig. 2) is a summary o f his conclusions. The horizontal meridian is represented at the base o f the calcarine fissure, the l ower visual field on its upper bank and lips; the upper visual field on its l ower bank and lips. The centre o f gaze is represented caudally, and the extreme periphery o f the visual field at t he anterior extremity o f the calcarine fissure. Inouye's figure also illustrates another fundamental fact o f organization o f the visual cortex. He shows t hat more cortex is devoted t o the representation o f the centre o f the visual field than t o the periphery. Some years later, Talbot and Marshal 1° coined the term ' magnification factor' t o mean the extent o f visual cortex in millimeters t hat represents one degree o f the visual field. Magnification is high in the centre o f gaze, and FromTatsujilnouye's monograph,showing hiscranio-coordinometer. Theslidesand scalespermitaccurate measurementsof entryandexit woundsin relationto the majorlandmarks on the head. e D arslellunll d er l inken H auptsehspbire. 165 ° 1 50' i 35 * 1 20" 1 05 ° 3 0" 150 oo the calcarine any o f his p there are diffe to central an succeed? Ino and an extr synthesize g individual ca been done b good crop o f patients in th Civil W ar com probably lies One o f the ture o f smal the L ebel r smokeless p o a harder cas previous wea Japanese W a Mosin-Nagan of about 7. velocity o f 62 considerably smaller than the Franco-P higher muzzl the skull, b u they produce brain. Japan hard, stable M ost of Inou that entered another leav between the patients lost several days Inouye's j ob determine h o pension was blinded. Inouye lef He studied published his lesions on vis London and become dire 1909 t o 196 during this la clinical resea ophthalmolog acuity. He di There hav Japanese an brain injuries 352 TINS, VoL 10, No. 9, 1 987 351 Saturday, November 6, 2010 Neurotechnique New Paradigm for Optical Imaging Temporally Encoded Maps of Intrinsic Signal Valery A. Kalatsky and Michael P. Stryker, 2003 Measures changes in cortical light reflectance following local neural activation. Reflectance changes due to changes in blood oxygenation levels. More active areas absorb more light. Measures peak activity of large groups of neurons Saturday, November 6, 2010 SC V1 Saturday, November 6, 2010 TOPOGRAPHY • Nobel Laureate, 1981 • Used ablation experiments in the frog to determine where regenerating neurons in the retina project Roger Sperry, 1913-1994 • Stated the chemoaffinity hypothesis to explain topographic mapping Saturday, November 6, 2010 3 ZOOLOGY: R. W. SPERRY TOPOGRAPHY 705 brain circuits, also seemed • Experiment: of infrom the standpoint tJ4 • because the optic theorySevere of a supposed ough nerve, then cut "bits of information" zygote to handle all the dethe involved in buildl decisionseye in half. on • Allow neurons to E this plan. ... e obtained recently seems to regenerate and irect experimental answer to determine where ions. This has come in the they project S ars from histological studies 1958 on the optic system of Sperry 1963, of hich I was joined in 1959FIG. 1.-Diagrammatic reconstructions PNAS . Attardi,4' 5 and in the past that chemical cues in in optic tracts and Sperry postulated regeneration patterns formed retina and r alf by Dr. Arora.1, I In a d rora. 2 by fibers (after Attardi and In tectum as form originating in different retinal half d b Dr. tectum are used to indicatedconnections Sperry4' I). halves, hink we have finally manonstrate quite directly by histological methods the postulated selectivity Saturday, November 6, 2010 Saturday, November 6, 2010 rior > anterior gr 2H) (Frisen et al. At E16, when the SC, EphA7 i gradient Sperry also thought these chemical cues might bestretchi ure 2A; Ciossek expressed in gradients, so people started looking remains unchang EphA7 becoming Retina and 2K). Thus, Ep ing formation of subsequently do the superficial la the stratum grise in layers that are and receive retin Figure 3. Summary of Topographic Map Defects in e p hrin - A 2 ; These RNA data e p hrin - A 5 Double Mutant Mice Arborizations from 26 temporal and 20 nasal injections in e p hrin analyses of SC A 2 ; e p hrin - A 5 mutant mice were plotted with respect to a region EphA ephrin-Aend of Figure 4. Ephrin-A2 and Ephrin-A5 Exprd showing a clear along the anteroposterior axis. Zero represents the anterior brain the SC, and 100 the posterior end. Each black dot represents a (A and B) RNA hybridizationthe ant between on parasag distinct arborization site. Each vertically aligned set of dots repretions. Lines indicate approximate anterio sents a single retinal labeling. sion in the retin developing SC. (A) Ephrin-A2 probe shows a high point 1995). Thus, Eph TOPOGRAPHY ￿/￿ ￿/￿ ￿/￿ ￿/￿ temporal nasal A Control P Figure ble M (A–D) P14 b (A and A (B and Brack arbori magn tissue mutan ventra tive in P positi Feldheim, et al. 2000, Neuron (E an ￿/ ￿ and Figure 1. Mapping Abnormalities in the SC of ephrin-A2 Saturday, November 6, 2010 antero ephrin-A knockout SUMMARY • The visual field can be divided into 4 quadrants • The left visual field is processed by neurons on the contralateral side of the brain • Nasal retinal ganglion cells cross to contralateral, temporal axons stay ipsilateral • The order of the visual field is maintained as information is relayed from the retina to image forming centers • Gradients of molecules are used to establish topographic maps Saturday, November 6, 2010 BREAK Saturday, November 6, 2010 IMAGE FORMING PROJECTIONS Saturday, November 6, 2010 THALAMUS dLGN receives direct input from retina, projects to V1 • 90% of the retinal axons go to the dLGN. • Layered structure: eye-specific and functionallyspecific • Layers align in order to align visual fields. • dLGN neurons have similar receptive fields to retinal ganglion cells (center-surround) • Low convergence (1-2 RGCs synapse onto each dLGN cell) Saturday, November 6, 2010 THALAMUS Projections are segregated by eye in different layers Visual field remains aligned Saturday, November 6, 2010 PARALLEL PROCESSING Different classes of RGCs project to different layers of the dLGN Saturday, November 6, 2010 PARALLEL PROCESSING Different classes of RGCs project to different layers of the dLGN M dLGN target Cell Body Receptive Field Action Potential Conduction Response Kinetics Cone Input P parvocellular small small slow sustained multiple K koniocellular medium medium fast ? blue magnocellular large large fast transient single type Motion Saturday, November 6, 2010 Color Nobody Knows PRIMARY VISUAL CORTEX • Receives input from dLGN, retinotopic • First site of visual processing for perception, receptive fields are different than in retina Saturday, November 6, 2010 PRIMARY VISUAL CORTEX • Superior visual field processed below calcarine sulcus, inferior above • Each takes a different route to V1 through the internal capsule • Meyer’s loop - Superior visual field information Saturday, November 6, 2010 Visual field defects • Spatial relationships in the retina are maintained in the brain and anatomy of these projections is known • Therefore, a 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. Saturday, November 6, 2010 VISUAL FIELD DEFICITS Diagnosing site of injury from effects on visual function Saturday, November 6, 2010 VISUAL CORTEX • The visual cortex (V1) is layered. Each layer has stereotypical inputs and outputs. • V1 is organized into columns: eye-specific and functionallyspecific • V1 is retinotopically organized • Receptive fields in V1 different from retina and dLGN elongated and specific to orientation Saturday, November 6, 2010 PRIMARY VISUAL CORTEX Organization of V1 - layers • The visual cortex is layered. • Each layer has stereotypical inputs and outputs. • LGN projects to layer 4, Output layer is layer 5. Saturday, November 6, 2010 PARALLEL PROCESSING Different layers of the dLGN project to different layers in V1 Saturday, November 6, 2010 PRIMARY VISUAL CORTEX Organization of V1 - ocular dominance columns • V1 is the first site in which inputs from the two eyes is merged • dLGN cells from Contra- & Ipsi- layers project adjacently in V1 • Eye-specific responses in layer 4, but find binocular cells in layer 2/3 Saturday, November 6, 2010 PRIMARY VISUAL CORTEX Organization of V1 - ocular dominance columns • Columns can be visualized by injection of radiolabel in one eye V1 dLGN Eye Saturday, November 6, 2010 PRIMARY VISUAL CORTEX Organization of V1 - ocular dominance columns Ocular Dominance Columns / Adams, Horton 67 • Or, cytochrome oxidase staining after deprivation of one eye ure 5. Human ocular dominance columns obtained using Hahn echo BOLD fMRI at 6, 2010 Saturday, November7 tesla. The image depicts a 3 mm thick Figure 6. Ocular dominance columns in the right striate cortex of PRIMARY VISUAL CORTEX Organization of V1 - ocular dominance columns Saturday, November 6, 2010 PRIMARY VISUAL CORTEX V1 is plastic - if deprive input from one eye, territory responsive to other eye expands Hensch, 2005 Saturday, November 6, 2010 reestablish the pattern during axonal re- anuran the modification of the chenmoaffinity hy- the transplant and without disturbing a similar translocation occurs in retinotectal map. The three-eyed generation suggest that highly specific Ranaarises pothesis, itthese experiments mammalian embryo, the question pipiens used in is proposed that graded affin- the two normal optic evaginations. All whether the interactions have two ities between cells of one part pre- to postsynaptic cell anomaly of crossing of optic complete retinal projectionsof the reti- operations were performed between in albino a field for one part the tectal field Shumway stages 17 to 19, before retinal axons may be involved (1). at the chiasm4 found innervating nal single previouslyof uninmammals (16) may be due nervated serve naive) tectal lobe from This theory of rigid retinal ganglionto an anomaly(that is, to orient the projection along topo- axons penetrate the brain but after the graphic of the translocated retinal early cell to tectal cell chemoaffinities has re-segment. development. axes. Competition between reti- retinal axes have been determined (8). In and GIRO The animals produced by imcently been challenged. ExpansionMARCUS JACOBSON V1 - ocular dominance columns Organization ofeither a were or left eye primorHIROSE the visual field projection planting right compression of Department ofAnatomy, College of following retinal or tectal ablations Utah, dium in the forebrain region of embryos Medicine, University of indicate a more plastic system 84132 In a with minimal dorsoventral rotation of Salt Lake City (2-5). modification of the chenmoaffinity hy- the transplant and without disturbing pothesis, it is proposed that graded affin- the two normal optic evaginations. All References d Notes ities between cells G. B. Lapashovof the reti- operations were performed between 1. of one part and 0. G. Stroeva, Development qf the tectal Program for Scientific nal field for one part of the Eye (Israel field Shumway stages 17 to 19, before retinal Translations, Jerusalem, 1963). 2. H. Petersen, Ergeb. Anat. Entwicklungsgesch. serve to orient the 24, 327 (1923); H. Woerdemann, Arch. Entwickprojection along topo- axons penetrate the brain but after the graphic axes. Competition between220 (1929); retinal axes have been determined (8). In C.-O. Jacoblungsmech. Org. 116, reti- PRIMARY VISUAL CORTEX Ocular dominance columns in Frogs? Normally not, but can be induced by introduction of a third eye son, J. Embryol. Exp. Morphol. 7, 1 (1959). 3. E. Manchot, Arch. Entwicklungsmech. Org. 116, 689 (1929); 0. Mangold, Ergeb. Biol. 7, 193 (1936). 5. M. Fischberg, Genetica 24, 213 (1949); J. Embryol. Exp. Morphol. 6, 393 (1958). 6. G. Fankhauser, Q. J. Exp. Biol. 20, 20 (1945). 7. P. D. Nieuwkoop and J. Faber, Normal Table of Xenopus laevis (Daudin) (North-Holland, Amsterdam, ed. 2, 1967). 8. R. C. Graham and M. J. Karnovsky, J. Histochem. Cytochem. 14, 271 (1966). 9. I. Simpson, B. Rose, W. R. Loewenstein, Science 195, 294 (1977). 10. G. Hirose and M. Jacobson, in preparation. 11. G. Fankhauser and T. Humphrey, Proc. Natl. Acad. Sci. U.S.A. 29, 341 (1943). 12. K. Straznicky and R. M. Gaze,J. Embryol. Exp. Morphol. 26, 67 (1971); M. Jacobson, Brain Res. 103, 541 (1976). 13. B. Mintz and S. Sanyal, Genetics 64 (Suppl.), 43 (1970). 14. E. van Deusen, Dev. Biol. 34, 135 (1973). 15. R. K. Hunt, personal communication. 16. R. W. Guillery, Brain Res. 14, 739 (1969); Sci. Am. 230 (No. 5), 44 (1974). 17. Supported by grant BNS-13910A from the National Science Foundation. 14 July 1978; revised 5 September 1978 SCIENCE, VOL. 202, 10 NOVEMBER 1978 Saturday, November 6, 2010 4. C. R. Stockard, Am. J. Anat. 15, 253 (1913); H. B. Adelmann, Q. Rev. Biol. 11, 161 and 284 (1931). Fig. 1. (a) Three-eyed Rana pipiens 8 months after metamorphosis. The central eye primordium was implanted at Shumway stage 17 from a similarly staged donor. The supernumerary eye has externally normal dimensions, but lacks a pupillary response. (b) Autoradiographic distribu, tions of grain densities in the optic tectum of a 3-month postmetamorphic three-eyed frog after of 3H]proline into the vitreous body of the normal eye. (Inset) Dark-field injection of 10 HuCi enlargment showing the pronounced segregation of labeled and unlabeled regions of the tectal neuropil. Constantine-Paton & 0036-8075/78/m1o10o639$00.50/0 Copyright 0 1978 AAASLaw, Science 1978 639 PRIMARY VISUAL CORTEX • Nobel Laureates, 1981 (shared w/ Sperry) • Described receptive fields of visual neurons in the thalamus and cortex Torsten Wiesel David Hubel • Worked on plasticity 19241926and development, too Saturday, November 6, 2010 PRIMARY VISUAL CORTEX Orientation Tuning Saturday, November 6, 2010 PRIMARY VISUAL CORTEX Receptive Fields are structured differently than in retina • Hubel and 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. Saturday, November 6, 2010 PRIMARY VISUAL CORTEX Simple cell receptive fields Saturday, November 6, 2010 PRIMARY VISUAL CORTEX Complex cells detect movement Saturday, November 6, 2010 PRIMARY VISUAL CORTEX Complex cells can be direction selective Saturday, November 6, 2010 PRIMARY VISUAL CORTEX Organization of V1 - orientation columns Saturday, November 6, 2010 PRIMARY VISUAL CORTEX Organization of V1 - orientation columns Saturday, November 6, 2010 PRIMARY VISUAL CORTEX Organization of V1 - orientation columns Saturday, November 6, 2010 PRIMARY VISUAL CORTEX Organization of V1 - orientation columns Pinwheels! Saturday, November 6, 2010 EXTRASTRIATE CORTEX • Cells in V1 project to several “higher” visual centers • As information flows out of V1, receptive fields become more and more precise • Can be divided into two streams: • Ventral - shape and object recognition (What?) • Dorsal - location and direction of movement (Where?) Saturday, November 6, 2010 EXTRASTRIATE V1 relays information to several visual areas that process higher order aspects of the visual scene Saturday, November 6, 2010 EXTRASTRIATE Visual areas specialized for different functions • Middle Temporal Area (MT) • Direction of a moving edge (any color) • V4 • Respond to color regardless of form • 10 areas total, lesions produce weird perceptions Saturday, November 6, 2010 EXTRASTRIATE Dorsal vs. Ventral “streams” Where? What? Saturday, November 6, 2010 EXTRASTRIATE Face Recognition - large areas in primates dedicated Saturday, November 6, 2010 Highly specified - e.g. Jennifer Aniston Neuron Saturday, November 6, 2010 EXTRASTRIATE or, Kobe Bryant neuron... Saturday, November 6, 2010 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. • Blind site - disruptions in V1 cause blindness. However some people can “guess” what an object is. Implies that there are other projections from eye to brain that can somehow compensate. Saturday, November 6, 2010 Weird visual defects Visual Hemi-neglect - lesion parietal lobe on one side Saturday, November 6, 2010 SUMMARY • Visual projection pathways are morphologically and functionally distinct, regulate different behaviors • e.g. magno v. parvo v. konio • Visual cortex is organized into columns, receptive fields shared across layers • Orientation columns - pinwheels, highly selective • Ocular dominance - input from two eyes merged in V1 • Extrastriate areas process distinct aspects of the visual scene • Ventral (what?) and dorsal (where?) streams Saturday, November 6, 2010 ...
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