INTRODUCTION: We present a novel microelectronic system for in vivo stimulation and recording of neuronal activity. The system is intended for use with multielectrode silicon probes and is based on a dedicated 64‑channel CMOS chip. It can generate complex sequences of microstimulation pulses and simultaneously record (with low artifacts) neuronal responses at up to 512 electrodes. The system is compatible with most silicon probes used in the brain research and can use up to four probes in parallel, providing bidirectional communication with populations of neurons simultaneously in several brain areas. Each channel of the chip includes a recording amplifier and a stimulation circuit. The amplifier has adjustable gain (110‑550x), low cut‑off frequency (1.4‑7 Hz), and anti‑aliasing filter frequency (1.2‑14 kHz). The input‑referred noise is 6.8 µV. Signals from all the channels are digitized at 40 kHz. The stimulation signal is defined independently for each channel with 40 kHz refresh rate. The stimulation artifacts are reduced by temporally disconnecting the amplifiers from electrodes and optimization of the pulse waveform. METHOD(S): The system has been tested in experiments exploring somatosensory thalamo-cortical network in rodents. 2‑3 weeks before surgery, animals received injections of AAV‑hSyn‑ChR2‑EYFP viral vector. In anesthetized animals, multichannel probes were inserted into the barrel cortex and/or sensory thalamus for recording of LFPs and multi-unit responses to microstimulation delivered to various nodes of thalamo‑cortical network. Electrically evoked activity was compared with responses to natural whisker deflection and optical stimulation. RESULTS: The reported system can generate complex patterns of stimulation pulses and record neuronal signals with very low artifacts at up to 512 electrodes, making it a powerful tool for mapping of the functional connections between brain circuits. FINANCIAL SUPPORT: Supported by Polish National Science Centre grant 2013/08/W/NZ4/00691.
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