Fig. 2

Comparison of data (left) to the model (right). a Average recording of 14 wild type flies measured in LD for 5 days; day/night shown with white/black bars. Model consists of four exponential terms with rates \(b_{MD} ,\,b_{MR}\), \(b_{ER}\), \(b_{ED}\), and widths of morning and evening peaks given by \(T_{M}\) and \(T_{E}\). b Autocorrelations of data and model with primary period 24 h. Periods in signal are found from regularly appearing peaks with high correlation. Peaks exceeding the dashed line \(2/\sqrt N\), where N is number of data points in activity trace, represent strong correlations. Strong 24 and 12 h periods are seen in both graphs. c Lomb–Scargle power spectra for the data and the model. Model reproduces strong peaks as well as small side peaks (arrows), which are from the Dirichlet kernel (see Additional file 1). Parameters used for this simulation: \(b_{MD} = - 0.81\,{\text{h}}^{ - 1} ,\,b_{MR} = 0.486\,{\text{h}}^{ - 1} ,\,b_{ER} = 0.09 \,{\text{h}}^{ - 1} ,\,b_{ED} = 3.6\,{\text{h}}^{ - 1} ,\,T_{M} = 5.3\,{\text{h}},\,T_{E} = 3.6\,{\text{h}}.\)