FREQUENCY-DEPENDENT SIGNAL TRANSFER IN NEURON TRANSISTORS

Nerve cells are attached to open, metal-free gates of field-effect tra nsistors submersed in electrolyte. The intracellular voltage is modula ted by small ac signals from 0.1 Hz to 5000 Hz using a patch-clamp tec hnique. The source-drain current is affected in amplitude and phase th rough a modulation of the extracellular voltage in the cleft between t ransistor and cell. The ac-signal transfer is evaluated on the basis o f linear response theory. We use the model of a planar two-dimensional cable which consists of the core of an electrolyte sandwiched between the coats of a cell membrane and silicon dioxide of the transistor su rface. Comparing experiment and model we obtain the resistances of cor e and coat, i.e., of the, seal of cell and surface and of the attached membrane. The resistance of the membrane varies in different junction s. It may be lowered by two orders of magnitude as compared with the f ree membrane. This drop pf the membrane resistance correlates with an enhancement of the seal resistance, i.e., with closer adhesion. The li near ac-transfer functions are used to compute the signal transfer of an action potential. The computed response is in good agreement with t he observations of excited nerve cells on transistors.