Noninvasive Recording of Neuronal Activity by Fieldeffect Transistors and Fluorescent Dyes

Abstract

Multisite recording of electrical activity of neurons is a prerequisite to investigate signal processing in arborized neurons and in neural nets. Such a method must be noninvasive and should detect changes of the intracellular voltage at a high spatio-temporal resolution. Two approaches are considered: (i) Influence-Technique [1]; A probe capacitor - silicon oxide on silicon - is attached to the neuron membrane. Part of the membrane potential drops across the probe capacitor. That voltage modulates the charge distribution in silicon which is observed by the source-drain current in field-effect transistor configuration. (ii) Field- Technique A charged probe molecule - amphiphilic dye - is bound to the neuron membrane. The electrical field at the site of the probe affects the location of the dye at the membrane/water-interface. Resolvation modulates the spectroscopic and photochemical properties of the probe as observed by fluorescence. The methods are tested with identified neurons of the leech which are cultivated with designed geometry of their arborizations [4,5].