Extracellular recording with transistors and the distribution of ionic conductances in a cell membrane

Intracellular voltage transients of cultured cells are recorded by transist ors and other planar electrodes as local extracellular voltages. The theore tical relationship between extra- and intracellular voltage is investigated with a two-compartment circuit using the approximation of a fast, weak and small cell-silicon junction. It is shown that extracellular recording reli es on the difference of specific ionic conductances in the attached and fre e regions of the cell membrane. The result rationalizes Various observation s with neuron transistors. It guides the optimization of extracellular reco rding and the development of cell-based chemical sensors.