Figure 1.

Confocal line-scan images showing Ca²⁺ sparks activated by a large depolarization after brief repriming of a depolarized fiber. Each image is a pseudo-color representation of ΔF/F₀. (A–C) Three images recorded at the same scan location for three applications of the same pulse protocol (540 ms repriming pulse to −90 mV, 400 ms test pulse to +40 mV, 600 ms return to −90 mV; top). (D) Same image as C but showing identified events fulfilling selection criteria i–iv enclosed in white boxes, and events fulfilling criteria i–iii, but not iv, in red boxes. Arrowheads indicate single triads for display of ΔF/F₀ time courses in Fig. 2A.