Spiral wave dynamics under pulsatory modulation of excitability

The dynamics of meandering spiral waves in the photosensitive Belousov-Zhabotinsky reaction is investigated under external forcing by single light pulses, periodic pulses, and feedback-controlled sequences of light pulses. The effect of a single stimulus on the trajectory of the spiral tip is related to the phase of the tip motion on the trajectory at the moment when the stimulus is applied. Periodic stimulation of the medium can produce spiral wave entrainment and resonance. A connection between the phase of the stimuli and the stability of the regime of entrainment is shown. In the feedback-controlled system each stimulus is applied at a moment corresponding to the passage of a wave front through a particular detection point. The introduction of such a feedback results in two new dynamic regimes, the entrainment and resonance attractor. Size and stability of these attractors are determined by the value of a time delay in the feedback loop. The experimental results are corroborated by numerical simulations performed with a modified two-component Oregonator model.