© 1999 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Nanomedicine, Volume I: Basic Capabilities, Landes Bioscience, Georgetown, TX, 1999

4.8.6.1 Electric Field Neurosensing

The "typical" ~20 micron human neuron discharges 5-100 times per second, moving from -60 mV potential to +30 mV potential in ~10^-3 sec. Thus the variation in electric field at the axonal surface is ± 4500 volts/m. Since electric field sensors can detect 100 volt/m fields up to GHz frequencies (Section 4.7.1), an electric sensor attached by circumaxonal cuff or pressed against the axonal surface (possibly at the node of Ranvier) should readily detect each action potential discharge. (The diameter of human nerve axons is 0.1-20 microns.⁷⁹⁹) By 1998 silicon-to-neuron extracellular junctions already permitted direct stimulation of individual nerve cells in vitro without killing the cells,⁵¹³ and extracellular electrodes were commonly used to detect neuronal electrical activity noninvasively, both in vivo⁵⁷³ and in vitro.^572,574,575 Artificial electric fields may also be employed to trigger or moderate neural signals (Section 7.4.5.6). Cell membrane capacitance is typically ~0.01 picofarads/micron²,²²⁸⁸ and varies with the state of the health of the cell.^2289,2290

Last updated on 17 February 2003