A geometric method for spatiotemporal coherent structure analysis
  We describe a geometric method to quantify wave patterns observed in the nervous system, which are non-stationary and with a mixture of spiral, target, plane and irregular waves. The method analyzes fluctuations of the energy angular distribution in two-dimensional Fourier spectrum of wave patterns, which reflects changes of the orientation distribution of wavefronts. We show that the number of the genuine peaks in generalized phase spectrum is close to the number of the coherent space-time clusters arising in wave patterns, and propose to use the number as a complexity measure. 
Chuan Zhang, Kentaroh Takagaki, Xiaoying Huang, Steven J. Schiff and   Jian-Young Wu
nlin.PS nlin.CD