Retinotopy of the face aftereffectIntroductionExperiment 1IntroductionMethodsPsychophysicsData analysisResultsExperiment 2IntroductionMethodsPsychophysicsData analysisResultsExperiment 3IntroductionMethodsPsychophysicsData analysisResultsDiscussionExperiment 1Size of face translation areaHemifield effectsEye fixationPossible interaction with sizeExperiment 2Sharpening of receptive fieldsShape contrast effectExperiment 3ConclusionsAcknowledgmentSupplementary dataReferencesRetinotopy of the face aftereffectSeyed-Reza Afraza,*, Patrick Cavanagha,baDepartment of Psychology, Harvard University, 33 Kirkland Street, Cambridge, MA 02138, USAbLaboratoire Psychologie de la Perception, Universite´Paris Descartes, Paris, FranceReceived 26 June 2007; received in revised form 5 October 2007AbstractPhysiological results for the size of face-specific units in inferotemporal cortex (IT) support an extraordinarily large range of possiblesizes—from 2.5° to 30° or more. We use a behavioral test of face-specific aftereffects to measure the face analysis regions and find a coarseretinotopy consistent with receptive fields of intermediate size (10°–12° at 3° eccentricity). In the first experiment, observers were adaptedto a single face at 3° from fixation. A test (a morph of the face and its anti-face) was then presented at different locations around fixationand subjects classified it as face or anti-face. The face aftereffect (FAE) was not constant at all test locations—it dropped to half its max-imum value for tests 5° from the adapting location. Simultaneous adaptation to both a face and its anti-face, placed at opposite locationsacross fixation, produced two separate regions of opposite aftereffects. However, with four stimuli, faces alternating with anti-facesequally spaced around fixation, the FAE was greatly reduced at all locations, implying a fairly coarse localization of the aftereffect.In the second experiment, observers adapted to a face and its anti-face presented either simultaneously or in alternation. Results showedthat the simultaneous presentation of a face and its anti-face leads to stronger FAEs than sequential presentation, suggesting that faceprocessing has a dynamic nature and its region of analysis is sharpened when there is more than one face in the scene. In the final exper-iment, a face and two anti-face flankers with different spatial offsets were presented during adaptation and the FAE was measured at theface location. Results showed that FAE at the face location was inhibited more as the distance of anti-face flankers to the face stimuluswas reduced. This confirms the spatial extent of face analysis regions in a test with a fixed number of stimuli where only distance varied.Ó 2007 Elsevier Ltd. All rights reserved.Keywords: Face aftereffect; Translation sensitivity; Object perception1. IntroductionThe surface of human retina is approximately 1100 mm2(Bron, Tripathi, & Tripathi, 1997). An ordinary object, likea face viewed at 1 m, spans about 10° and covers about11 mm2on the retina, 1% of its area. In every day vision,this relatively small image can land anywhere on the retinaengaging widely diverse neural popul ations on the retinaand early retinotopic brain areas. Proper visual functionrequires objects to be recognized across all these possiblelocations, a property called translation invariance or toler-ance (for review see: Shepard & Cooper, 1982; Walsh &Kulilowski, 1997). Translation invariance could be sup-ported by many independent local analyses as is the casefor early visual features like orientati on, color, motion,and spatial frequency (Chalupa & Werner, 2003 ). How-ever, it is less plausible that the extensive computationsrequired for object recognition could be duplicated overmany locations. Nevertheless, the human visual system isable to toler ate large degrees of retinal translation—at leastin priming preparations (Biederman & Cooper, 1991; Ellis,Allport, Humphreys, & Collis, 1989)—and the alternativeis that the large receptive fields in object-anal ysis areas ofthe brain provide the neural substrate for translationalinvariance.Inferior temporal (IT) cortex is the major brain arearesponsible for object recognition (Logothetis & Sheinberg,1996; Tanaka, 1996) and face recognition (Afraz, Kiani, &Esteky, 2006). Although there is no exact equivalent formonkey IT in the human brain (see Orban, Van Essen, &0042-6989/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.doi:10.1016/j.visres.2007.10.028*Corresponding author.E-mail address: [email protected] (S.-R. Afraz).www.elsevier.com/locate/visresAvailable online at www.sciencedirect.comVision Research 48 (2008) 42–54Vanduffel, 2004), human cortical areas LO, STS and FFAshow selective responses to faces and express similaritieswith monkey IT (see Kanwisher & Yovel, 2006 for review).Early electrophysiological recordings from IT cortexreported very large receptive fields—even as wide as30°—for IT neurons (Gross, Rocha-Miranda, & Bender,1972). Large receptive fields for IT cells are also reportedin later studies (Desimone, Albright, Gross, & Bruce,1984; Missal, Vogels, Li, & Orban, 1999; Tovee, Rolls, &Azzopardi, 1994). Moreover, the selectivity of IT neuronsto highly complex stimuli such as faces is largely indepen-dent of the stimulus location within their large receptivefields (Ito, Tamura, Fujita, & Tanaka, 1995; Logothetis,Pauls, & Poggio, 1995; Schwartz, Desimone, Albright, &Gross, 1983; Tovee et al., 1994). On the other hand, someelectrophysiology studies have reported much smallerreceptive fields for IT neurons (Op de Beeck & Vogels,2000), even as small as 2.5° in diameter (Dicarlo & Maun-sell, 2003). Even for IT cells with large receptive fields,absolute firing levels may vary with retinal location (Sch-wartz et al., 1983), a response modulation that can carryinformation about object location within the receptive fieldboundary. There is also recent fMRI results showing reti-notopy in human face selective brain areas (Rajimehr, Van-duffel, & Tootell, 2007). Also, in another recent fMRIstudy, Hemond, Kanwisher, and Op de Beeck (2007) foundstrong contralateral preference in FFA and other facerelated areas. The large discrepancy between different stud-ies possibly results from the wide range of experimentalpreparations and procedures they used. Overall, given thevariation in experimental details, species and results in allthese