Fig. 6: Intracellular activity response function constructed from single-cell measurements on Dictyostelium.
From: Emergence of collective oscillations in adaptive cells
a Upper panel: The average cytosolic cAMP level (the activity \(a\), arbitrary unit) in response to a step increase of 1 nM extracellular cAMP at \(t=0\) (reproduced from Fig. 2a in ref. 3). Lower panel: The response function \({R}_{a}(t)\) estimated from the derivative of the response data in the upper panel. b The corresponding phase shift \({\phi }_{a}\) in the low frequency regime (red curve), obtained from the Fourier transform of \({R}_{a}(t)\). Onset oscillation frequencies in experiments reside in the green region (see Fig. 2b in ref. 2). Also shown is the phase shift \(-{\phi }_{s}\) from Eq. (6) at \({\tau }_{s}=0.35\) min (blue curve), the extracellular signal clearance time to yield an onset oscillation period of about 8 min. Faster signal clearance shortens the oscillation period towards the theoretical lower bound at around 6.28 min.
