Bistability and Stabilization of Human Visual Perception under Ambiguous Stimulation

We discuss a computational model that describes stabilization of percept choices under intermittent viewing of an ambiguous visual stimulus at long stimulus intervals. Let Toff and Ton be the time that the stimulus is off and on, respectively. The behavior was studied by direct numerical simulation in a grid of (Toff, Ton) values in a 2007 paper of Noest, van Ee, Nijs, and van Wezel. They found that both alternating and repetitive sequences of percepts can appear stably, sometimes even for the same values of Toff and Ton. Longer Toff, however, always leads to a situation where, after transients, only repetitive sequences of percepts exist. We incorporate Toff and Ton explicitly as bifurcation parameters of an extended mathematical model of the perceptual choices. We elucidate the bifurcations of periodic orbits responsible for switching between alternating and repetitive sequences. We show that the stability borders of the alternating and repeating sequences in the (Toff, Ton) -parameter plane consist of curves of limit point and period-doubling bifurcations of periodic orbits. The stability regions overlap, resulting in a wedge with bistability of both sequences. We conclude by comparing our modeling results with the experimental results obtained by Noest, van Ee, Nijs, and van Wezel