This proposal is to investigate the application, to neural recording and stimulation, of two dimensional microelectrode integrated circuit arrays that have been developed by the DoD as the readout structure for infrared imaging. The self scanning capability of these integrated circuit microelectrode structures allows thousands of electrodes to be addressed via a few electrical connections. And in some versions, each microelectrode has an adjacent preamplifier built into the array itself to increase sensitivity. The Phase I study will include experimental measurements of the sensitivity of these electrode arrays in sensing electric fields of the strength and character found near the surface of the brain. In Phase II actual measurements of rat brain neural activity will be made.