Section: New Results

Visual Neuroscience

Neural fields models for motion integration: Characterising the dynamics of multi-stable visual motion stimuli

Participants : Olivier Faugeras, Pierre Kornprobst, Guillaume S. Masson [Institut de Neurosciences de la Timone, UMR 6193, CNRS, Marseille, France] , Andrew Meso [Institut de Neurosciences de la Timone, UMR 6193, CNRS, Marseille, France] , James Rankin.

We are investigating the temporal dynamics of the neural processing of a multi-stable visual motion stimulus with two complementary approaches: psychophysical experiments and mathematical modelling. The so called “barber pole” stimulus is considered with an aperture configuration that supports horizontal (H), diagonal (D) or vertical (V) perceived directions for the same input. The phenomenon demonstrates an interesting variable and dynamic competition for perceptual dominance between underlying neural representations of the three directions. We study the temporal dynamics of this phenomenon with a neural fields, population-level representation of activity in MT, a cortical area dedicated to motion estimation. Numerical tools from bifurcation analysis are used to investigate the model's behaviour in the presence of different types of input; this general approach could be applied to a range of neural fields models that are typically studied only in terms of their spontaneous activity. The model reproduces known multistable behaviour in terms of the predominant interpretations (percepts) of the barber pole stimulus.

We probe the early processing from stimulus presentation to initial perceived direction (before perceptual reversals). The basic dynamic properties of the early transition from D to H/V are well predicted by the model. This work has been presented in the European Conference on Vision Perception (ECVP) [38] , [41] and it has been published in [23] .

We are extending this work to investigate the longer term dynamics for which perceptual reversals are known to occur, due to competition between 1D motion cues aligned with the grating's motion direction and 2D motion cues aligned with aperture edges. This work has been presented in the Vision Sciences Society 12th Annual Meeting (VSS) [39] , [42] .