Van Essen3Organization of Visual Cortexregions, plus a visuotopic mapp - PDF document

Van Essen3Organization of Visual Cortexregions, plus a visuotopic mapping analysis ofdorsal occipital cortex (Galletti et al 1999). WhileAlthough there are many similarities, thesepartitioning schemes differ in many ways, forimpediments faced by cortical cartographers. (i)Subtle boundaries. The distinctions betweenneighboring regions are often subtle, even whenInternalheterogeneity. Many (perhaps most) visual areasare internally heterogeneous. This heterogeneitymodularity (repetitiveorganization at a finer scale than the overall arealasymmetries (differences betweenthe representations of the upper (superior) andlower (inferior) visual fields; or internalgradients (gradual shifts in characteristics ratherthan discrete modularity). (iii) Individualvariability. The overall size of well-definedvisual areas such as V1 and MT can vary two-boundaries relative to gyral and sulcal landmarksA compelling case for areal identification entailsfinding region-specific characteristics that areclusters discussed below.The differences among partitioning schemes canbe categorized along four lines: Terminologicalequivalence. Some differences are essentiallyterminological, in that different labels areLumping vs.Splitting. Some regions are considered a singlearea by some investigators (the “lumpers”) but astwo separate areas by other investigators (the“splitters”). This is an issue, for example, forBoundary uncertainty. Evenwhen there is a consensus on the identity of anarea and the main criteria for its identification,publication; and (iv) inaccuracies or distortionsarising when registering data to the atlas.. In some regions,partitioning schemes differ more profoundly than computerized flat maps. D. A composite map of partitioning schemes for occipital cortex (Lyon and Kaas, 2002, theirbe accessed via http://brainmap.wustl.edu:8081/sums/archivelest.do?archive_id=448857. Occipital visual areas. V1 and V2 are bothlarge, well-defined areas, with V1 occupying2) in the atlas righthemisphere. V1 and V2 have a mirror-symmetric visuotopic organization, with thevertical meridian represented along theirand the two subregions differ in the globalpattern of thick stripes, thin stripes, and inter-Area V3 was originally identified as a strip ofcortex that adjoins V2 and has mirror-symmetric2A-C). More significantly, evidence forpronounced dorso-ventral asymmetries inV3d and V3v are subdivisions of a single areaV3. A sensible interim strategy is to designateV4 is a moderately-sized area whose lower-field(V4d) and upper-field (V4v) representations arevisuotopic organization of dorsal V4 appears tobe more complex and variable across individualsmore pronounced dorso-ventral asymmetrieshave been reported for the corresponding regionFive additional areas adjoin or closely approachV2 along its dorso-medial and ventro-medialof which includes an upper-field as well as alower-field representation (Colby et al., 1988;Felleman and Van Essen, 1991; Lyon and Kaas,2002). Area PO as charted by Colby et al.posterior portion of TF, identified as VTF byBoussaud et al. (1991), is visually responsive buthas at best a crude visuotopic organization.Dorsal temporal and posterior parietal cortex. The “dorsal stream” of visual areas ( Chapter 34,sulcus, plus the dorsal part of the superiortemporal sulcus. Area MT, the most extensivelyidentified as V4t (Ungerleider and Desimone,1986, Felleman and Van Essen, 1991) or MTcA major target of MT is the MST complex(orange in Fig. 2), which lies dorsal and medial 1986, Fig. 2B) includes a visuotopically organizedtopographic and connectional data, includes three Van Essen7Organization of Visual Cortex naturally of interest to have a current estimate of Van Essen8Organization of Visual Cortexfunctionally distinct subdivisions of visuallyresponsive cortex, but for some the evidencea credible case for at least three dozen distinctareas. The number of areas that show clear12, depending on designation of zones vs. areas.Coping with multiple schemes, arealuncertainties, and individual variability. Severalgeneral observations emerge from the precedingfor quantifying and visualizing the uncertaintiesassociated with charting areal boundaries and theatlas (Van Essen et al., 2001a).Another important issue involves the options foraccessing and extracting information from surface-alternative is to use computerized visualizationsoftware to access atlas data more efficiently andhyperlinks included in the figure legends) andviewing the maps using the freely available Caretlocation by latitude and longitude (cf. Fig. 1E);encoding uncertainty limits for each boundary; andHuman visual cortex. The analysis of human visualcortex has benefited greatly from the advent ofhemisphere of a surface-based atlas (the"Human.Colin" atlas) that was generated fromsets (see the legend to Fig. 4). Based on theseprovisional assignments, cortex that is2)in the right hemisphere of the atlas. ByHuman area V1 (area 17) has a well-definedarchitectonic boundary that runs near the marginsof the calcarine sulcus but with considerable Van Essen9Organization of Visual Cortex quality and supercedes the Visible Man surface-based atlas previously published (Van Essen and Drury, charted using the most likely boundary in theRademacher et al. study) is 21 cm2, or 2.2% ofcerebral cortex. This is about one-sixth of itsfractional occupancy on the macaque atlas.Neuroimaging studies have revealed numerousvisuotopically organized extrastriate areas inaddition, tests for motion-related activation haveconsistently demonstrated a prominent focus inhas therefore been identified as human MT+(Tootell et al., 1995) or as V5 (Watson et al.,Figure 5 includes many visuotopic areas thatwere mapped onto the human atlas using surface-macaque, suggesting a marked evolutionarydivergence in the relative sizes of nearby cortical Van Essen10Organization of Visual Cortexinstead of a single V3A, with V3B being locatedmore posterior (lower on the flat map). Area V7Human area V4v lies antero-lateral to VP/V3vand contains a mirror-symmetric upper-fieldrepresentation. Interestingly, cortex lateral anddorsal to V4v, identified as LO (Van Oostende etGrill-Spector etal. (1998a,b; 2001), includesmost of LOC/LOP but extends further ventrallyTests using a variety of stimuli and behavioralparadigms besides those just discussed havespecialization. Ventral occipito-temporal cortexcontains a region preferentially activated byfoci involved in analysis of faces, houses, andchairs are concentrated in a region (red dottedOther studies suggest that these may notconstitute distinct areas but rather a functionalIn the parietal lobe, visually-related activationshave been reported in a large swath of cortex ineye movements, visual motion, and spatialanalyses (Haxby et al., 1994; Corbetta et al.,Macaque-Human comparisons.While there are many striking similarities invisual cortical organization between macaqueand human, there are numerous differences as useful general strategy for examining theseMT+; and the boundaries of neocortex along the foveal V2 and to the Sylvian fissure) is more . Comparisons between macaque and human visual cortex using interspecies surface-based digitally from the outset, registering such data to DPdorsal prelunate areaFSTfloor of superior temporal areaIPaarea IPa from Cusick et al., (1995)LIPdlateral intraparietal (dorsal)LIPvlateral intraparietal (ventral)MDPmedial dorsal parietal areaMIPmedial intraparietal areaMSTmedial superior temporal areaMTmiddle temporal areaPIPposterior intraparietal areaPOparietal-occipital areaTAaarea TAa from Cusick et al., (1995)TEadantero-dorsal division of TETEav antero-ventral division of TETFtemporal area FTHtemporal area HTpttemporo-parietal areaTPOctemporal parietal occipital (caudal)TPOitemporal parietal occipital (intermediate)TPOrtemporal parietal occipital (rostral)VIPventral intraparietalVIP*heavily myelinated subdivision of VIPV1visual area 1V2 visual area 2V3visual area 3V3Avisual area V3AV4visual area 4V4tV4 transitional areaVOTventral occipitotemporal areaVPventral posterior area7avisual area 7a46visual area 46LOPlateral occipital parietalMSTmedial superior temporal areaMSTddorsal subdivision of MSTMSTl lateral subdivision of MSTMSTda dorso-anterior subdivision of MSTMSTdp dorso-posterior subdivision of MSTMSTm medial subdivision of MSTVIPllateral subdivision of VIPVIPmmedial subdivision of VIPV4taV4 transitional area (anterior)V4tpV4 transitional area (posterior)7allateral area 7aDMOcx Dorso-medial occipitalITcxInferotemporal complexMSTcxMedial Superior temporalMTccaudal to Middle TemporalPOa-eexternal division of areaPOa-iinternal division of area POaPPcxPosterior parietal complexTE1subdivision 1 of TETE1-3ddorsal subdivision of TE1-3TE1-3vventral subdivision of TE1-3TE2subdivision 2 of TETE3subdivision 3 of TETEa/msubdivisions a and m of TETEmmedial division of TETPOtemporo-pareital-occipitalV2ddorsal division of V2V2vventral division of V2V3ddorsal division of V3V3vventral diivision of V3V6visual area 6V6AVisual area 6AVSTcxVentral superior temporal the macaque. J. Comp. Neurol. 306: 554-Exp. Brain Res. 80: 49-53. Corbetta, M., Akbudak, E., Conturo, T.E., Snyder,A.Z , Ollinger, J.M.,Drury, H.A.,Linenweber, M.R., Raichle, M.E., VanCusick, C.G. (1997) The superior temporal 248: 164-189. Desimone, R. and Ungerleider (1989) Neuralmechanisms of visual processing inmonkeys. Handbook of Neuropsychology,DeYoe, E.A., Carman, G., Bandetinni, P., Glickman,S., Wieser, J., Cox, R., Miller, D., and Neitz,visual areas in human cerebral cortex. Proc.Natl. Acad. Sci. USA 93:2382-2386.Drury, H.A., Van Essen, D.C., Corbetta, M., &Snyder, A.Z. (1999) Surface-based analysesof the human cerebral cortex. In: Brain environment. Nature 392: 598-601.system. NeuroImage 9:195-207. Van Essen17Organization of Visual CortexHaxby JV, Gobbini MI, Furey ML, Ishai A, SchoutenJL, Pietrini P. Distributed and overlappingHolmes, C.J., Hoge, R., Collins, L., Woods, R., Toga,A.W. and Evans, A.C. (1998) Enhancement333.Ishai, A., Ungerleider, L.G., Martin, A., Schouten,J.L., Haxby, J.V. (1999) DistributedKaas, J.H. (1997) Theories of visual cortexorganization in primates. In: Cerebral Cortex, stimulation. J. Neurophysiol., 60: 621-644. Rhesus monkey. J. Neurosci. 4: 1690-1704. Olavarria,, J.F. and Van Essen, D.C. (1997) TheOram and Penett 1996. Integration of form andprimate extrastriate cortex. In: Cerebral (15):4757-Seltzer, B., and D.N. Pandya (1980) Converging 315: 322-325. Smith, A.T., Grenlee, M.W., Singh, K.D., Kraemer,F.M. and Hennig, J. (1998) The processingof first- and second-order motion in humanTaira M, Tsutsui KI, Jiang M, Yara K, Sakata H.Parietal neurons represent surfacedisparity. J Neurophysiol. 2000inferotemporal cortex. In: Cerebral Cortex, Van Essen, D.C., Newsome, W.T. & Maunsell, J.H.R. Van Essen19Organization of Visual CortexZeki, S., McKeefry, D. J., Bartels, A., & Frackowiak,R. S. J. (1998) Has a new color been Organization of Visual Areas in Macaque and Human Cerebral Cortex David C. Van EssenIn: Visual Neurosciences (L. Chalupa and J. Werner, eds.)In Press 8/15/03 -- Proof versionIntroduction.The mammalian visual system containsnumerous visual areas that collectively occupy aset of objectives is to identify in key species ofinterest the overall extent of visual cortex, thestudied species. Our fragmentary and rapidlyevolving understanding is reminiscent of theThe primary objective of this chapter is tosummarize our current understanding of visualprimate and has been charted using a widevariety of approaches. Human visual cortex,surface-based atlases offer many advantages overconventional atlases (e.g., stereotactic atlases andcomplex data in a convenient and electronically-accessible format; (iii) represent various types ofcomparisons of cortical organization.Visual areas in the macaque monkey.cortex in the macaque and its relationship to2002; see legend to Fig. 1 for details). The toppanels show lateral and medial views,The dotted lines on the flat map represent theestimated boundary between regions dominatedconsiderable intermixing of function intransitional regions between modalities. Theauditory (red, 3%), motor (magenta, 8%), andolfactory (brown, 1%). Unassigned cortex (gray, Figure 1. Visual cortex and other functional modalities mapped onto a surface-based atlas of macaquecerebral cortex. The atlas was generated from a high-resolution (0.5 mm3 voxels) structural MRI volumegenerously provided by N. Logothetis (Case F99UA1, M. mulatta), using the SureFit segmentation methodfor surface reconstruction and Caret software for surface manipulation and flattening (Van Essen et al.,2001a). This atlas has many advantages over its predecessors, which include manually generated maps(Van Essen and Maunsell, 1980; Felleman and Van Essen, 1991) and surface-based atlases from ahemisphere that lacked corresponding structural MRI data (Van Essen et al., 2001a). A. Lateral view. B.Medial view. C. Flat map. Surface coloring represents different functional modalities, as identified on theflat map; darker shading represents cortex buried in sulci. D. Lateral view of the atlas spherical map, withlatitude and longitude isocontours. By convention, the lateral pole is set at the ventral tip of the centralsulcus. E. Latitude and longitude isocontours displayed on the flat map. Data for Figures 1-3 can beaccessed via http://brainmap.wustl.edu:8081/sums/archivelist.do?archive_id=448857.Figure 1 also shows latitude and longitudeisocontours that are determined on a sphericalmap (Panel D) and projected to the flat map(Panel E). As with earth maps, sphericalcoordinates provide a concise and objective wayto specify precise locations on the map (Drury etal, 1999; Fischl et al., 1999a,b; Van Essen et al.,2001a).The identification of distinct visual areas isgenerally based on finding reliable differences inone or more characteristics related to: (i)architecture, (ii) connectivity, (ii) visualtopography, and/or (iv) functional characteristics(Felleman and Van Essen, 1991, Kaas, 1997).Using various combinations of these criteria,numerous partitioning schemes for visual cortexin the macaque monkey have been published overthe past century. Figure 2 shows 10 such schemesthat were mapped to the atlas using a surface-based registration method (Van Essen et al., 1998,2001b; see legend to Fig 2 for details). Panels A-C illustrate three schemes that encompass most orall of the visual cortex. The Felleman and VanEssen (1991) and Ungerleider and Desimone(1986) schemes are based on anatomical andphysiological data from many sources. The Lewisand Van Essen (2000a) scheme is based on anarchitectonic analysis of multiple hemispheres,with the atlas map generated via surface-basedregistration of a particular individual map. PanelD shows several schemes that cover morerestricted regions, including a connectivity-basedanalysis of occipital cortex (Lyon and Kaas, 2002)and architectonic analyses of temporal andparietal cortex (Seltzer and Pandya, 1978, 1980,1986). Panel E shows two additional architectonicschemes covering temporal (Baylis et al., 1987)and parietal (Preuss and Goldman-Rakic, 1991)