Mode shapes oscillate over time.
(a) Variations in mode scores over time for the top five modes for two example growth cones. Note the clear oscillations, particularly for R1 (reflective mode 1) in the top row and S1 (symmetric mode 1) in the bottom row. (b,c) Autocorrelation and Fourier power spectra for all significant modes from the above two growth cones. (d) Analysis of oscillations for another example growth cone, this time showing much longer-period oscillations in R1. (e) Shuffle control for the growth cone from panel (d). Randomly shuffling the positions of all frames within the movie destroys oscillations. This is seen most clearly by the presence of very weak power, spread across many frequencies, in the Fourier power spectrum. We also shuffled all frames across the entire dataset 10,000 times, and calculated the mean total power and peak power. In all 10,000 cases these mean power values were less than for the unshuffled data. Autocorr, autocorrelation.