Figure 4. Optical control of spiral wave chirality in cardiac monolayer.

a, Snapshots from an ongoing anticlockwise spiral wave (frames 2,000–2,160), an optically applied computer-generated clockwise spiral wave (frames 2,240–2,480) and the persisting spiral wave post-chirality reversal (frames 2,560–2,720). b, Activity traces from the red and blue pixels indicated in a, showing four light-controlled chirality reversals. Computer-generated spirals were imposed at random phases for less than two rotations, as seen in the four higher-intensity transients. Black arrows indicate the time period presented in a. Red and blue arrows indicate the switch of order of excitation at the chosen locations due to chirality reversal. c, Activation maps for the initial spiral wave and the four resultant spirals after each of the chirality reversals. See Supplementary Movies 4 and 5 for minimally processed and colourized data, respectively (for more details see Supplementary Fig. 3).