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

2. 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

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

4. Tanaka and Saito, ´89

5. L. Lagae et al. ´94

6. Orban et al PNAS 1992

7. 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

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

9. 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

10. STIMULI  

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

12. Y. Liu et al, J Neurosci, ´04 100 spikes/sec A B TEs: CONVERGENCE OF 3D SHAPE CUES: STEREO AND TEXTURE

16. 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

17. 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

18. 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

19. 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?

20. 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

21. 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

23. 23 Srivastava et al., 2007 Janssen et al., 2000 Interaction: (Curved stereo-curved monocular) - (Flat stereo-flat monocular) Joly et al 2007 Poster 462.4 Monday pm

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

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

26. 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

27. Integrated Project NeuroProbes FP6: IST-027017.