Interferometric detection of action potentials.

Individual action potentials in axons can be detected in vitro using intrinsic optical signals. The principles of this detection technique are described here. The technique has been demonstrated using neuronal axons dissected from lobster. It would also be applicable to axons and active dendrites of cultured neurons with diameters somewhat larger than an optical wavelength. Using index-matching techniques, it may be possible to extend the technique to smaller structures.