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Mathematical operations in the visual brain Guy A. Orban Laboratorium voor Neuro-en Psychofysiologie K.U. Leuven Medical School

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1)Do neurons perform mathematical operations? What is being measured? 2)Gradient selective neurons: a new family 3)Do we have the same neurons in our brain

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AIP MT/V5 MSTd FST TEs Dorsal pathway Ventral pathway V1

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Tanaka and Saito, ´89

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L. Lagae et al. ´94

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Orban et al PNAS 1992

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1)Do neurons perform mathematical operations? What is being measured? 2)Gradient selective neurons: a new family 3)Do we have the same neurons in our brain

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G. Orban et al, Trends in Neurosci, ´06 ORDRES DE DISPARITE: DERIVEES SPATIALES DE LA DISPARITE ordre zero premier ordre second ordre approximations

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D.K. Xiao et al, Eur. J. of Neurosci., ´97 Neurone MT/V5 sélectif pour le gradient de vitesse et, indirectement, pour la direction du tilt (inclinaison en profondeur) Gradient haut-bas Gradient droite-gauche A B EXTRACTION DE LA FORME 3D DU MOUVEMENT: NEURONES

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STIMULI

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G. Orban et al, Trends in Neurosci, ´06 TEs: SELECTIVITE POUR LA DISPARITE D´ORDRE SUPERIEUR

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Y. Liu et al, J Neurosci, ´ spikes/sec A B TEs: CONVERGENCE OF 3D SHAPE CUES: STEREO AND TEXTURE

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K. Nelissen et al, The JoNS, ´06 EXTRACTION DE LA FORME 3D DU MOUVEMENT: fMRI SINGE EVEILLE Aires sensibles au mouvement et extraction de la forme 3D du mouvement

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Premier Ordre: surface inclinée (8 orientations) Second ordre: surface cylindrique (4 orientations) Second ordre: bosseSecond ordre: selle (2 orientations) EXTRACTION DE LA FORME 3D DU MOUVEMENT: NEURONES Tests pour les neurones FST

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The family of gradient selective neurons Gradients of speed: linear: MT/V5, MSTd, FST higher order: FST Gradients of disparity: linear: TEs, CIP, AIP, higher order: TEs, AIP, Premotv Gradients of texture: linear: CIP, TEs

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1)Do neurons perform mathematical operations? What is being measured? 2)Gradient selective neurons: a new family 3)Do we have the same neurons in our brain?

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Monkey Single cells Monkey fMRI Human fMRI Neural basis fMRI Homologies Scouting Monkey needs to be awake fMRI is also an efficient tool to test drug effects

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fMRI: SENSITIVITY TO CURVATURE in DEPTH Binocular disparity Stereo Monocular Two eyes: different images Two eyes: same images Curved (same profiles as used in single cell) Surfaces Flat

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23 Srivastava et al., 2007 Janssen et al., 2000 Interaction: (Curved stereo-curved monocular) - (Flat stereo-flat monocular) Joly et al 2007 Poster Monday pm

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Selection of subjects (n=22) 3D shape adjustment task

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Interaction: (Curved stereo-curved monocular)- (Flat stereo-flat monocular) L & R Post ITG (6-7) L & R DIPSA (15-16)

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Conclusions 1 Even if they seem to perform mathematical operations, neurons match input to a template 2 New family of gradient selective neurons: match input to first and higher order gradients 3 Through the combination of single cell recording with fMRI in the awake monkey and humans we can show that similar neurons exist in the human brain

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Integrated Project NeuroProbes FP6: IST

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