Implantable neurotechnologies: a review of integrated circuit neural amplifiers <s> Amplifier and electrode co-design <s> This active probe can be used for the long-term recording of extracellular neural biopotentials and as a basis for closed-loop neural prostheses. The probe incorporates on-chip circuitry for amplifying, multiplexing, and buffering neural signals recorded from ten recording electrodes spaced 100-/spl mu/m apart. It requires only three leads and operates from a single 5-V supply. On-chip self-test circuitry for testing electrode impedance levels is provided. The on-chip circuitry is fabricated in a die area of 1.3 mm/SUP 2/ using 6-/spl mu/m LOCOS enhancement-depletion NMOS technology, and dissipates 5 mW of power. The probe is 4.7 mm long and 15 /spl mu/m thick, and has a shank which tapers from 160 /spl mu/m near the base to less than 15 /spl mu/m near the tip. <s> BIB001 </s> Implantable neurotechnologies: a review of integrated circuit neural amplifiers <s> Amplifier and electrode co-design <s> This paper describes the development of a high-density electronic interface to the central nervous system. Silicon micromachined electrode arrays now permit the long-term monitoring of neural activity in vivo as well as the insertion of electronic signals into neural networks at the cellular level. Efforts to understand and engineer the biology of the implant/tissue interface are also underway. These electrode arrays are facilitating significant advances in our understanding of the nervous system, and merged with on-chip circuitry, signal processing, microfluidics, and wireless interfaces, they are forming the basis for a family of neural prostheses for the possible treatment of disorders such as blindness, deafness, paralysis, severe epilepsy, and Parkinson's disease. <s> BIB002 </s> Implantable neurotechnologies: a review of integrated circuit neural amplifiers <s> Amplifier and electrode co-design <s> A 256-site, fully implantable, 3-D neural recording microsystem has been developed. The microsystem incorporates four active neural probes with integrated circuitry for site selection, amplification, and multiplexing. The probes drive an embedded data-compression ASIC that successfully detects neural spikes in the presence of neural and circuit noise. The spike detection ASIC achieves a factor of 12 bandwidth reduction while preserving the key features of the action potential waveshape necessary for spike discrimination. This work extends the total number of neural channels that can be recorded across a transcutaneous inductively coupled wireless link from 25 to 312. When a spike is detected, this ASIC serially shifts the 5-bit amplitude and 5-bit address of the spike off of the chip over a single 2.5 Mb/s wired or wireless line. The spike detection ASIC occupies 6 mm/sup 2/ in 0.5 /spl mu/m features and consumes 2.6 mW while the entire microsystem consumes 5.4 mW of power from a 3-V supply. <s> BIB003 </s> Implantable neurotechnologies: a review of integrated circuit neural amplifiers <s> Amplifier and electrode co-design <s> A high-resolution PDMS-based conformable microelectrode array (cMEA) with integrated electronics is implemented. The cMEA is incorporated into individual layers of a nanofiber-based nerve regeneration scaffold to create a novel regenerative electrode scaffold (RES) capable of establishing a stable, high-resolution peripheral nerve interface. The device features a compact size with an enhanced signal-to-noise ratio (SNR), as required by implantation applications. Preliminary characterizations of the device are performed using in vitro experimentations, including impedance spectroscopy and neural culturing. <s> BIB004 </s> Implantable neurotechnologies: a review of integrated circuit neural amplifiers <s> Amplifier and electrode co-design <s> Neural probes have become the most important tool for enabling neuroscientists to place microelectrode sensors close to individual neurons and to monitor their activity in vivo. With such devices, it is possible to perform acute or chronic extracellular recordings of electrical activity from a single neuron or from groups of neurons. After the many developments in neural implants, it has become clear that large arrays of electrodes are desirable to further investigate the activity performed by complex neural networks. Therefore, in this paper, we propose a CMOS neural probe containing 455 active electrodes in the probe shank (100 μm wide, 10 mm long, and 50 μm thick) and 52 simultaneous readout channels in the probe body (2.9 × 3.3 mm2). In situ amplification under each electrode enables low-impedance interconnection lines, regardless of the electrode impedance, with a residual crosstalk of -44.8 dB. This design has been implemented in a 0.18-μm standard CMOS technology, with additional CMOS-compatible post-processing performed at wafer level to define the electrodes and the probe outline. In this architecture, the analog front-end achieves an input-referred noise of 3.2 μVrms and an NEF of 3.08. The power consumption of the core circuit is 949.8 μW, while the total power consumption is 1.45 mW. The high-density active-electrode array in this neural probe allows for the massive recording of neural activity. In vivo measurements demonstrate successful simultaneous recordings from many individual cells. <s> BIB005 </s> Implantable neurotechnologies: a review of integrated circuit neural amplifiers <s> Amplifier and electrode co-design <s> Thin-film longitudinal intrafascicular electrodes (tf-LIFE) are widely used for peripheral nerve recordings. tf-LIFEs are also promising electrodes for neural signal acquisition in future peripheral nerve prostheses. However, common mode signal interference, and electrical artifacts originating from long wire leads and wire movement are known problems encountered when using such electrodes, which lead to degradation in the recording quality. Here, we report an active tf-LIFE electrode implemented by integrating a neural amplifier chip die in close proximity to a tf-LIFE electrode. Consuming only 1mW and measuring 37 mm×7.2 mm×2.4 mm, this active tf-LIFE electrode creates a reliable connection and considerably shortens the distance between the electrode site and neural amplifier. This active electrode has demonstrated repeatable in-vivo recordings of compound action potentials from the rat sciatic nerve. Our results show that this electrode is suitable for repeated in-vivo recordings of compound action potentials from nerves in applications such as peripheral and visceral nerve interfaces that require low-noise stable nerve recordings. <s> BIB006
The advantages of integrating neural amplifiers as close as possible to the electrode site were first demonstrated in BIB001 . Numerous works BIB004 BIB003 BIB002 have since built upon this achievement, particularly to scale up the number of electrodes and amplifier channels. Recently, Lopez et al. reported the integration of a 455-active electrode amplifier onto a single shank of a silicon probe (Fig. 11a) BIB005 . Guo et al. also reported the co-integration of extrafascicular (Fig. 11b ) BIB004 with neural amplifiers, while Ng et al. reported integrating intrafascicular (Fig. 11c) BIB006 peripheral nerve electrodes with neural amplifiers. The trend of building highly integrated systems is ongoing. However, the challenges regarding integrating CMOS processing (for the IC design) with MEMS processing (for the electrodes and sensors) remain, which include biocompatible hermetic sealing of the IC to prevent moisture absorption and seepage along with active electronic components. Of course, amplifier/electrode co-design introduces more stringent area and power constraints on the neural amplifiers, as they must fit the smaller form factor of the electrode while maintaining low amplifier input-referred noise. Fig. 11 Integration of amplifiers and electrodes a for cortical interfacing BIB005 , b for extrafascicular peripheral nerve interfacing BIB004 and c intrafascicular peripheral nerve interfacing BIB006 . Reproduced with permission from IEEE