Domain-specific cortical areas Two Sides of the Same Brain Fusiform - PowerPoint PPT Presentation

Face and Word Processing: Domain-specific cortical areas Two Sides of the Same Brain  Fusiform Face Area (FFA)  Visual Word-Form Area (VWFA) David C. Plaut  Parahippocampal Place Area (PPA) Marlene Behrmann  Extrastriate Body Area (EBA) Department of Psychology  Fusiform Body Area (FBA) Carnegie Mellon University Center for the Neural Basis of Cognition Faces and words N170 waveform specific to faces Bilateral homologous activation FFA VWFA R L R L Malach et al. Cohen et al. 2004 TREE vs. /tri:/ Carmel et al. (2002) x= –42, y= –57, z= –15 x= 40, y= –55, z= –10

Faces and words: ERP N170 waveform for letter strings L R L R L R Bentin et al. (1999) Rossion et al. (2003) Maturation of FFA Lesions to FFA  Prosopagnosia − Visual recognition much poorer for faces vs. other objects − Can be bilateral but right lesion suffices − Rely on other cues for recognition R R R Scherf et al. (2007)

FFA adjacent to central visual information Lesions to VWFA Levy et al. (2001), Malach et al. (2002)  Pure alexia − Impairment in word recognition in premorbidly literate adults − Left occipitotemporal lesion − No general language impairment − Rely on sequential “letter-by-letter” strategy Faces, words and eccentricity Hemispheric model Hasson et al. (2003)

Faces Houses Words

Scale variation X-Y coordinates Polar coordinates central peripheral central peripheral Acquisition Receptive/ projective fields Central vision

Lesioning Receptive/ projective fields method  For each horizontal Peripheral vision position (central to peripheral) in each hemisphere, remove three adjacent columns of intermediate (fusiform) units  Measure recognition performance on faces and houses (across all scales)

Predictions Domain generality  Domain generality Pure alexia − Ventral temporal-occipital cortex involved in any fine- grained visual discrimination  Bilateral participation − Unilateral lesions impact both faces and words  Competition for representation − Degree of face and word specialization related within individuals Same-different matching Linear effect of visual complexity Reaction Time (ms) + Visual Complexity

Bilateral participation Words: Lexical decision Predicted extent of impairment Alexia Controls Prosop. Words RT Faces Face discrimination (errors): Competition for representation Controls < Alexia < Prosop. Match-to-sample task: words or faces % Errors within-field between-field

Left-field advantage for faces Right-field advantage for words Individual distribution Correlation Compare magnitudes of within-field advantage for faces (left field) vs. words (right field)

Conclusions  Distributed cortical network for faces and words − Different representations, similar computations  Reliance on high visual acuity − Fine-grained discriminations  Topographic constraints on learning − Bias for local connectivity  Graded functional specialization − Both within and between hemispheres