256-channel reconfigurable system for recording the electrophysiological activity of a neural tissue in vitro

We present a measurement system for 256-channel in vitro recordings of brain tissue electrophysiological activity. The system consists of: brain tissue life support system, Microelectrode Array (MEA), 4 Application Specific Integrated Circuits (ASIC´s) for signals conditioning, Digitizer and PC Application for measurement, data presentation and storage. The life support system keeps brain tissue samples in appropriately saturated artificial cerebrospinal fluid at a very stable temperature. The MEA consists of 256, 40 μm diameter tip shaped electrodes. The ASIC´s perform amplification and filtering of the 256 field and action potential signals while the Digitizer performs simultaneous data acquisition from 256 channels with 14 kS/s sample rate and 12bit resolution. The resulting byte stream is transmitted to PC via USB (Universal Serial Bus). Preliminary tests confirm that the system is able to keep the extracted brain tissue active (hippocampal formation slices) and to record action potentials as well as local theta field potentials with very small amplitudes from multiple neurons simultaneously.