Fig. 4.

Wave-to-wave interactions in two dimensions. Wave-to-wave interactions caused rotating spiral waves. The preparation is a 6 × 6-mm² patch from rat visual cortex (top left, schematic diagram), also known as a tangential cortical slice. (Top) The voltage-sensitive dyes (VSD) signal of the oscillation induced by carbachol and bicuculline. (Bottom) The images are made from five consecutive oscillation cycles marked by the line under the top trace; each row of images is from one of the cycles. The first two rows of images show that the wave started from a pacemaker at the bottom of the imaging field and propagated upward in a “ring wave” pattern. During the third cycle, the ring wave was broken up into two wave fronts and the two fronts collided (third row, marked by the arrow). A rotating spiral wave was generated afterward with a wave front. In the fourth and fifth rows, this spiral wave front started to rotate in the field of view and continued rotating for the next 20 to 30 cycles (not shown).