NeuraPlex - High-density fully-immersible subcortical neural data digitizer based on time-division multiplexing

点击翻译按钮获取中文摘要

The objective of this research project is to develop and implement the first high-density fully-immersible CMOS neural probe with a spatial resolution lower than 50 µm. The state of the art is limited on one hand by conventional active neural-probes with a small electrode pitch but encompassing a large base and a high number of connecting wires. On the other hand, it offers a fully immersible CMOS neural probe featuring a minimal base and requiring fewer connections at the cost of a large electrode pitch. The new probe advances the state of the art by implementing an optimized signal processing chain tailored to this application. Hence, neither a bulky connector is required nor elaborate circuits need to be integrated into the base, which in turn yields a slim probe with a small electrode pitch and a uniform width from tip to base. Thus, substantial silicon area and costs can be saved. In addition, the probe can be fully immersed into the brain tissue whereby subcortical recording of single-neuron signals with a high signal-to-noise ratio, a large bandwidth and an appropriate spatial resolution becomes feasible.The objective will be met by integrating a “digital” multi-electrode-array into the shank. However, since the available area per channel on the shank is limited, multiple electrodes will need to share one analog-to-digital converter (ADC). Time-division multiplexing as performed up to now requires preamplifiers and an explicit anti-aliasing filter to be implemented on the base leading to a large area. To achieve the same on the limited area of the shank and still avoid excessive power consumption and temperature increase of the tissue, a dedicated ADC architecture needs to be developed. This ADC must meet, amongst others, the specifications of smallest-area, minimal-power consumption, and ultra-low-noise as defined by the high-density fully immersible CMOS neural probe. Fundamental research will thus be performed on architectures for continuous-time, incremental Delta-Sigma ADCs. Their intrinsic anti-aliasing filter as well as their applicability in multiplexed sensor systems make them the perfect candidate for neural recording systems.The resulting high-density neural probe with its capability to simultaneously monitor the single activity of hundreds of neurons will provide neuroscientists with new opportunities for performing research on brain activity in deeper regions and for gaining understanding of neural networks. Moreover, combined with a neural stimulator, it can be used to implement a closed-loop system and thus contribute to the pursuit of relieving the symptoms of neurological and psychological diseases.Due to the ever-increasing demand for ultra-low-power, high-resolution, multi-channel ADCs, the outcome of the fundamental research on architectures for continuous-time incremental Delta-Sigma ADCs are of high impact for other applications such as instrumentation and measurement or the Internet of Things.