A Bidirectional High-Voltage, High-Precision System for Neural Signal Stimulation and Recording

We present a high-voltage, high-precision multi-channel system capable of stimulating neural activity through bi-phasic pulses of amplitude up to ±50 V while recording very low-voltage responses as low as tens of microvolts. Most of the systems presented fromreported from the scientific community [1], [2] possess at least one of the following common limitations: low stimulation voltages, low gain capabilities, or insufficient bandwidth to acquire a wide range of different neural activities. While systems can be found that present remarkable capabilities in one or more specific areas, a versatile system that performs on all these aspects is missing. Many novel materials, like silicon carbide, are emerging as biocompatible interfaces [3], and more specifically as neuronal interfaces, and it is very useful to have a system which worksoperating across a wide range of voltages and frequencies for both physiological and electrical compatibility testing. The system presented here features a ±50 V bi-phasic pulse generator, 62 to 100 dB software selectable amplification, and a wide 30 Hz to 11 kHz bandwidth. The system architecture is well explained in [4] and [5]. For a 64 electrode microelectrode array (MEA) any electrode pair can be selected for stimulation of the brain slice, while the remaining 63 electrodes simultaneously read the very low voltage response. The low-noise, low-voltage devices of the system front end are protected by a unity gain BJTs stage, the end of the amplification and filtering chain are time domain multiplexed to an ADC, and the intercepted signal waveforms are transferred to a personal computer for data processing and storage. A 3-channel (one for stimulation and two for recording) prototype has been developed in order to verify the proposed architecture is capable of accurately stimulating and recording neural activity. We have successfully tested the stimulation unit. First, a C57BL/6J hippocampal slice was obtained and found to be capable of long term potentiation (LTP) using commercial tools (A-M Systems Model 1800 amplifier and 2200 isolation stimulator; Digidata Model 1440A low-noise data acquisition system). We detached the stimulation electrode pair from the AM-Systems Model 2200 and connected to our stimulator. We connected a Tektronix TDS 1002B Digital Oscilloscope to the output of the Digidata Model 1440A. A 100 Hz bi-phasic stimulation pulse was applied to the CA2/3 Schaffer’s collaterals and subsequent field excitatory post synaptic potentials (fEPSPs) in the CA1 stratum radiatum were received and recorded by the Tektronix (Figure 1) through the A-M Systems Model 1800. Testing of the recording electronics is currently in progress at the time of this report. Figure 1 – fEPSP CA1 hippocampal response generated by the stimulation circuit. The response is amplified 1000 times (horizontal resolution: 10 ms/div , vertical resolution: 5V/div). REFERENCES [1] T.L. Hanson, B. Omarsson, J.E. O’Doherty, I.D. Peikon, M. Lebedev, M.AL. Nicolelis, "High-side Digitally Current Controlled Biphasic Bipolar Microstimulator", IEEE Transactions on Neural Systems and Rehabilitation Engineering, VOL. X, NO. X, MMXI 2011 [2] I. Obeid, M. Nicolelis, P.D. Wolf, “A Low Power Multichannel Analog Front End for Portable Neural Signal Recordings”, Journal Neuroscience Methods, 133(1-2), 27-32, 2004. [3] C.L. Frewin, M. Jaroszeski, K.E. Muffly, M. Peters, E. Weeber and S.E. Saddow, "Atomic Force Microscopy Analysis of Central Nervous System Cell Morphology on Silicon Carbide and Diamond Substrates", Journal of Molecular Recognition, Vol. 22, pp. 380 - 388, 2009. [4] L. Abbati, C.L. Frewin, P. Placidi, S.E. Saddow, A. Scorzoni, “Design and simulation of a 64 channel, high voltage analog interface for stimulation and acquisition of neural signals" Advances in Sensors and Interfaces (IWASI), 2011 4th IEEE International Workshop on, pp. 45-50. [5] S.E. Saddow Silicon Carbide Biotechnology: A Biocompatible Semiconductor for Advanced Biomedical Devices and Applications Elsevier, © 2012.