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NJIT Mathematical Biology Seminar

Tuesday, October 19, 2010, 2:30pm
Cullimore Hall 611
New Jersey Institute of Technology

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A model for dynamical switching during tristable perception of visual plaids

Gemma Huguet

Center for Neural Sciences, New York University

When observers view for an extended time an ambiguous visual scene with two or more different interpretations they report switching between different perceptions. Binocular rivalry is a well-known example of perceptual bistability (two perceptions), for which different mechanistic models have been proposed. However, attempts to generalize these models to stimuli with more than two competing percepts are scarce in the literature. In this talk, we will focus on experiments with two superimposed drifting gratings (plaids), identical except for their movement directions (normal to their respective orientations). There are two sources of ambiguity: their relative motion and the depth order. If the angle between the normal vectors for motion is small, coherence is favored (the gratings move together as a single pattern). If the angle is large, transparency is favored (the gratings slide across one another). For some range of angles, tristable perception is experienced: a coherent percept and two transparent percepts with alternating depth ordering. We will present a firing rate-based neural network model for the dynamics of alternations during perceptual tristability for plaids. The model involves stochastic dynamics of multiple-attractor systems. We have tested two different architectures: (a) three populations compete at the same level (b) two pairs of populations compete hierarchically. We will discuss the different results the two architectures yield to. This is joint work with John Rinzel (NYU)