The Responses of Isolated Nerve Fibers in Culture to Applied DC Voltages

Abstract

The notion that applied gradients of voltage could provide directional information to growing nerve fibers probably began with the studies of Sven Ingvar in 1920. For the next 60 years (for example, Weiss 1934 to Sisken and Smith 1975) this subdiscipline of neuroscience remained controversial, and a clear unambiguous demonstration that extracellular voltages could indeed direct the growth of nerve fibers was not provided in these earlier reports. This was in part due to the technical inability of the times to precisely measure the magnitude or geometry of applied extracellular fields within culture chambers, and a yet immature understanding of substrate interactions with growing nerve fibers. The most thoughtful and accomplished early investigation was performed by Gordon Marsh and Harold Beams at Iowa State University, the year of my birth, in 1946. The first well-controlled modern demonstration of electrical-field responses by neurites growing out of explanted chick dorsal root ganglia was by Lionel Jaffe and Moo-ming Poo in 1979. This report rendered all previous experiments obsolete.