Search

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. [ABSTRACT FROM PUBLISHER]

Our report is on the simulation results and the design of the integrated circuit dedicated for inductive powering of a neural recording system on a chip. Four different voltage rectifiers were considered. designed to compare their power efficiency, drop out voltages, and ability to work in a megahertz range. Each of the full bridge rectifiers is equipped with voltage clamps to prevent it from the high coil voltages. Presented circuits are dedicated for carrier signals in the range of a few MHz and load current of 10mA. Performance of the circuits is discussed based on the post-layout simulations. The circuit was designed in 180nm CMOS process and sent to fabrication. [ABSTRACT FROM PUBLISHER]

This paper presents the design methods that allow to drastically limit an area of a recording channel in multichannel integrated circuits dedicated to neurobiology experiments. The techniques that are presented in this paper allow to apply them in a 3D pixel multichannel integrated systems where area limitations are very strict. Furthermore, these allow one to minimize main problems e\ xisting in modern submicron processes i.e. leakage currents, an ability of obtaining very large MOS based resistances or a uniformity of main parameters of recording channels. For further improvement of the recording channels we designed and processed in a 180nm CMOS technology two recording channels that differ from one other in channel feedback components. The measurement results show that our methods allow to tune the lower cut-off frequency in a very large range, i.e. 10 mHz – 300 Hz. The upper cut-off frequency can be changed into two different modes, i.e. neural spike recording mode where it is equal to 9 kHz or slow biomedical signals recording mode where it can be changed in the 10 Hz – 280 Hz range. The voltage gain of the recording channels can be switched either to 260 V/V or to 1000 V/V. The input referred noise of the recording channel is equal to 5 µV while its power consumption is equal to only 11 µW. The single recording channel occupies only 0.06 mm2 of the chip area and together with its large functionality allows one to adapt it into modern 3D pixel multichannel neurobiology applications. [ABSTRACT FROM PUBLISHER]