Voltage-Sensitive Dye Imaging

Directly optically reads out membrane voltage across a wide area of tissue at once, using a dye whose fluorescence brightness shifts in real time with the electric field across the membrane it's embedded in.

References

• Salzberg, B.M., Davila, H.V., Cohen, L.B. "Optical Recording of Impulses in Individual Neurones of an Invertebrate Central Nervous System." Nature 246, no. 5434 (1973): 508–509.