Fig 4 -

A-E Effect of applying a light pulse (filled yellow rectangle) (0.092 mW/mm², 100 ms) to different phases of an action potential (AP). A₀ and A₁ refer to the APD₉₀ values of the unperturbed and perturbed AP, respectively. F Dependency of A₁/A₀ on the percentage of repolarization of the cell membrane at the start of stimulation (for different PWs). G PW-dependence of the percentage repolarization, at the start of a stimulation that causes maximum increase (blue) or decrease (brown) in APD₉₀. The dashed blue and brown lines on A correlate the findings in (G) to real values of the membrane voltage. The blue and brown arrows in A indicate where the light stimulus should be applied in order to achieve maximum increase or decrease in APD₉₀, respectively.