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We present canard-mediated mixed-mode oscillations (MMOs) arising in a model for the alternating pulse and surge pattern of gonadotropin releasing hormone (GnRH) secretion. The model is formed by two FitzHugh-Nagumo (FHN) oscillators that evolve on different timescales, with a feedforward coupling from the slow one (regulating system) to the fast one (secreting system). The resulting 4D model involves three different timescales. So far, global and local features of the model have been studied in the context of slow-fast dynamics and mixed-mode oscillations where folded singularities and associated canard trajectories have a particular importance. For instance, so-called secondary canards due to a folded node are responsible for the presence of a plateau with small oscillations in the model output, after the surge and before the return to pulsatility. In this poster, we focus on another canard-mediated slow-fast transition in the system, occurring in between the end of the pulsatility phase and the beginning of the surge. We study the effect of the type of the folded singularity on this delayed transition. |
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