Measuring synchrony in the mammalian central circadian circuit

Methods Enzymol. 2015;552:3-22. doi: 10.1016/bs.mie.2014.10.042. Epub 2014 Dec 26.


Circadian clocks control daily rhythms in physiology and behavior across all phyla. These rhythms are intrinsic to individual cells that must synchronize to their environment and to each other to anticipate daily events. Recent advances in recording from large numbers of cells for many circadian cycles have enabled researchers to begin to evaluate the mechanisms and consequences of intercellular circadian synchrony. Consequently, methods have been adapted to estimate the period, phase, and amplitude of individual circadian cells and calculate synchrony between cells. Stable synchronization requires that the cells share a common period. As a result, synchronized cells maintain constant phase relationships to each (e.g., with cell 1 peaking an hour before cell 2 each cycle). This chapter reviews how circadian rhythms are recorded from single mammalian cells and details methods for measuring their period and phase synchrony. These methods have been useful, for example, in showing that specific neuropeptides are essential to maintain synchrony among circadian cells.

Keywords: Circadian; Fourier transform; Period gene; Rayleigh plot; Synchronization Index; Vasoactive intestinal polypeptide.

Publication types

  • Research Support, N.I.H., Extramural
  • Review

MeSH terms

  • Animals
  • Circadian Rhythm*
  • Single-Cell Analysis
  • Suprachiasmatic Nucleus / physiology