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.
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