Design of a analog front-end for high-precision acquiring excitatory postsynaptic field potentials in the hippocampal Schaffer-CA1 neuronal pathway

The field excitatory postsynaptic potentials (fEPSPs) plays a crucial role in neural signal transmission and synaptic plasticity. Achieving high-precision acquisition and long-term reliable recording of neuronal fEPSPs is a key challenge. This paper presents the design of a analog front-end (AFE) system for the Schaffer-CA1 pyramidal neurons in the hippocampus, based on FPGA. The system employs a capacitance-free chopper front-end amplifier with a current-balanced architecture and a digitally controlled two-stage amplifier to achieve dynamic gain adjustment. A combination of a digital FIR filter and the filtfilt algorithm is used to implement zero-phase filtering. Experimental evaluations of long-term stability, frequency response, and dynamic response were conducted, demonstrating that the AFE can accurately acquire weak signals in the range of 160-360 μV. It achieves a high gain of 72-74 dB within the 1-300 Hz frequency band, with a theoretical gain error of less than 2.5%. Based on this system, fEPSPs acquisition experiments were conducted on synapses of Schaffer-CA1 neurons in ex vivo hippocampal slices. The results show that the AFE accurately captures fEPSPs and long-term potentiation (LTP) before and after induction. Compared with commercial MEA systems, the normalized amplitude difference was less than 5%, the correlation coefficient was greater than 0.82, and the normalized mean square error was less than 0.01. These results confirm that the designed AFE meets the requirements for precise acquisition and stable long-term recording of neuronal fEPSPs signals.