Emergence of chimera states in a neuronal model of delayed oscillators

Neurons are traditionally grouped in two excitability classes, which correspond to two different responses to external inputs, called phase response curves (PRCs). In this paper we have considered a network of two neural populations with delayed couplings, bound in a negative feedback loop by a positive PRC (type I). Making use of both analytical and numerical techniques, we derived the boundaries of stable incoherence in the continuum limit, studying their dependance on the time delay and the strengths of both interpopulation and intrapopulation couplings. This led us to discover, in a system with stronger delayed external compared to internal couplings, the coexistence of areas of coherence and incoherence, called chimera states, that were robust to noise. On the other hand, in the absence of time delays and with negligible internal couplings, the system portrays a family of neutrally stable periodic orbits, known as "breathing chimeras."