Fig. 10

Breathing instability from direct numerical simulation with parameters $\alpha =5$, $\beta =0.5$, $\gamma =4$, coupling strength $g=0.5$ and Heaviside threshold $h=0.12/(1+g)$. Initial data was constructed from a stationary spot solution by modifying the adaptation variable to a top-hat shape. Top and bottom rows: snapshots of activation u and adaptation a, respectively, at times indicated by orange lines in the middle row. Middle row: above threshold radii as function of time. See also the video in Additional file 6.