Mathematical operations in the visual brain

Guy A. Orban

Laboratorium voor Neuro-en Psychofysiologie

K.U. Leuven Medical School

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

AIP

MT/V5 MSTd FST

TEs

Dorsal pathway

Ventral pathway

V1

Tanaka and Saito, ´89

L. Lagae et al. ´94

Orban et al PNAS 1992

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

G. Orban et al, Trends in Neurosci, ´06

ORDRES DE DISPARITE: DERIVEES SPATIALES DE LA DISPARITE

ordre zero

premier ordre

second ordre

approximations

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

STIMULI

G. Orban et al, Trends in Neurosci, ´06

TEs: SELECTIVITE POUR LA DISPARITE D´ORDRE SUPERIEUR

Y. Liu et al, J Neurosci, ´04

100 spikes/sec

A

B

TEs: CONVERGENCE OF 3D SHAPE CUES: STEREO AND TEXTURE

K. Nelissen et al, The JoNS, ´06

EXTRACTION DE LA FORME 3D DU MOUVEMENT: fMRI SINGE EVEILLE

Aires sensibles au mouvement et extractionde la forme 3D du mouvement

Premier Ordre: surface inclinée(8 orientations)

Second ordre: surface cylindrique (4 orientations)

Second ordre: bosse Second ordre: selle (2 orientations)

EXTRACTION DE LA FORME 3D DU MOUVEMENT: NEURONES

Tests pour les neurones FST

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

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?

Monkey Single cells Monkey fMRI Human fMRI

Neural basis fMRI HomologiesScouting

Monkey needs to be awake

fMRI is also an efficient tool to test drug effects

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

Srivastava et al., 2007

Janssen et al., 2000

Interaction: (Curved stereo-curved monocular)- (Flat stereo-flat monocular)

Joly et al 2007

Poster 462.4Monday pm

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

Interaction: (Curved stereo-curved monocular)- (Flat stereo-flat monocular)

L & R Post ITG (6-7)

L & R DIPSA (15-16)

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

Integrated Project NeuroProbes FP6: IST-027017.