Functional Analysis of V3A and Related Areas in HumanVisual CortexRoger B. H. Tootell,1Janine D. Mendola,1Nouchine K. Hadjikhani,1Patrick J. Ledden,1Arthur. K. Liu,1John B. Reppas,1Martin I. Sereno,2and Anders M. Dale11Nuclear Magnetic Resonance Center, Massachusetts General Hospital, Charlestown, Massachusetts 02129, and2Department of Cognitive Sciences, University of California at San Diego, La Jolla, California 92093-0515Using functional magnetic resonance imaging (fMRI) and corti-cal unfolding techniques, we analyzed the retinotopy, motionsensitivity, and functional organization of human area V3A.These data were compared with data from additional humancortical visual areas, including V1, V2, V3/VP, V4v, and MT (V5).Human V3A has a retinotopy that is similar to that reportedpreviously in macaque: (1) it has a distinctive, continuous mapof the contralateral hemifield immediately anterior to area V3,including a unique retinotopic representation of the upper visualfield in superior occipital cortex; (2) in some cases the V3Afoveal representation is displaced from and superior to theconfluent foveal representations of V1, V2, V3, and VP; and (3)inferred receptive fields are significantly larger in human V3A,compared with those in more posterior areas such as V1.However, in other aspects human V3A appears quite differentfrom its macaque counterpart: human V3A is relatively motion-selective, whereas human V3 is less so. In macaque, the situ-ation is qualitatively reversed: V3 is reported to be prominentlymotion-selective, whereas V3A is less so. As in human andmacaque MT, the contrast sensitivity appears quite high inhuman areas V3 and V3A.Key words: fMRI; V3A; retinotopy; motion selectivity; visualcortex; MT/V5; human; primateAfter cortical visual areas V3 and V4 were identified and namedin macaque monkeys, another region was discovered betweenthem and named “V3 accessory” (V3A) (Van Essen and Zeki,1978; Zeki, 1978a,b). V3A is now regarded as a cortical area thatis entirely independent and distinct from its similarly namedneighbor, V3, in terms of its retinotopy (Van Essen and Zeki,1978; Zeki, 1978a,b; Gattass et al., 1988), its histology (Burkhal-ter et al., 1986; Felleman and Van Essen, 1987; DeYoe et al.,1990; Girard et al., 1991; Tootell and Taylor, 1995; Felleman etal., 1997), its functional properties (Felleman and Van Essen,1987; Gaska et al., 1987, 1988) and its connections (for review, seeGaska et al., 1988; Felleman and Van Essen, 1991). Thus thename V3A is misleading, but it is retained here because ofhistorical convention.V3A occupies a position in the hierarchy of cortical visual areasthat is intermediate between lower tier areas (e.g., V1) and highertier areas (e.g., inferotemporal cortex). V3A shares connectionswith areas in both parietal and temporal cortex (for review, seeGaska et al., 1988; Felleman and Van Essen, 1991) Unlike otherretinotopic areas in superior occipital cortex (Van Essen andZeki, 1978; Gattass et al., 1988), macaque V3A has a completerepresentation of lower and upper visual fields. However, furtherdetails of the retinotopy within V3A remain unclear (Van Essenand Zeki, 1978; Zeki, 1978b; Gattass et al., 1988; Van Essen etal., 1990; Felleman et al., 1997).Although there are few single unit reports from this region,some interesting properties have been reported (Gaska et al.,1987; Galletti and Battaglini, 1989). Single units in area V3 arereported to be commonly motion- and direction-selective (Felle-man and Van Essen, 1987; Gegenfurtner et al., 1994) (but seeZeki, 1978b), presumably reflecting the distinctive input fromlayer 4B of primary visual cortex (Lund and Boothe, 1975;Burkhalter et al., 1986; Van Essen et al., 1986). However, suchmotion and direction selectivity is apparently much less prevalentin V3A (Zeki, 1978b; Gaska et al., 1988; Galletti et al., 1990)(Joris et al., 1997). Another notable feature of this general regionis the unique distinction in connections and functional propertiesbetween the complementary quarter-field representations in ma-caque areas V3 versus VP (Burkhalter et al., 1986).The intriguing but incomplete nature of the data on V3A andneighboring areas suggested that follow-up studies would beworthwhile. These areas also were experimentally appealing be-cause the borders of these areas can be defined by retinotopiccriteria, eliminating ambiguity about where one is sampling func-tional activity. Furthermore, V3A and some of its neighborsoccupy intermediate levels in the visual processing hierarchy—thus study of these areas could clarify the nature of processing athigher levels while being tractable enough to activate with rela-tively simple visual stimuli, as in lower tier areas.Ideally, such information might be obtained from correspond-ing areas in human visual cortex to test and extend previousinformation from the macaque. Although such experiments nec-essarily are limited by the restricted nature of noninvasive tech-niques available for use in humans, the recently developed func-Received April 11, 1997; revised June 27, 1997; accepted July 2, 1997.This study was supported by the Human Frontiers Science Program and NationalEye Institute Grant EY07980, both to R.T. J.M. was supported by the McDonnelPew Foundation. N.K.H. was supported by Swiss Fonds National de la RechercheScientifique. This study could not have been done without the generous support ofthe Massachusetts General Hospital Nuclear Magnetic Resonance Center. We areparticularly grateful to Mary Foley for scanning support and to Bruce Rosen, RobertSavoy, Ken Kwong, Stephan Brandt, and Sean Marett for fruitful discussions andmore pragmatic support. The machine shop at the Rowland Institute furnishedvaluable plastic hardware.Correspondence should be addressed to Dr. Roger B. H. Tootell, Nuclear Mag-netic Resonance Center, Massachusetts General Hospital, 149 Thirteenth Street,Charlestown, Massachusetts 02129.Copyright © 1997 Society for Neuroscience 0270-6474/97/177060-19$05.00/0The Journal of Neuroscience, September 15, 1997, 17(18):7060–7078tional magnetic resonance imaging (fMRI) technique couldfurnish maps of the cortical topography in adequate detail.Do such corresponding areas actually exist in human visualcortex? Retinotopic imaging studies have revealed apparent hu-man homologs of retinotopic macaque areas V1, V2, V3, and VP(Schneider et al., 1993; DeYoe et al., 1994, 1996; Sereno et al.,1995; Shipp et al., 1995; Tootell et al., 1995a, 1996b;