Spiral wave chimeras in nonlocally coupled excitable FitzHugh–Nagumo neurons

Chimera states in excitable systems have received extensive attention in recent years. However, the spiral wave chimera in a two-dimensional excitable system has not been observed yet. In this study, we investigate spiral wave chimeras in two-dimensional nonlocally coupled excitable FitzHugh–Nagumo neurons. Depending on the relative coupling radius and the coupling phase, we find spiral wave chimeras numerically. We also find a novel spiral wave pattern, the spiral wave amplitude death chimera, characterized by a non-excited core. By exploring the phase diagram of different spiral wave chimera dynamics, we find the transition between spiral wave chimeras with an incoherent core and spiral wave amplitude death chimeras with a non-excited core when the coupling phase crosses $\pi /2$. We also find that large $a$ (the parameter in the FitzHugh–Nagumo neuron) favors the spiral wave amplitude death chimera.