Micro-Electronics for autonomous neural implants

用于自主神经植入的微电子学

• 批准号: 2699078
• 金额: --
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2016
• 资助国家: 英国
• 起止时间: 2016 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2699078
• 关键词: Micro; Electronics; autonomous; neural; implants

Implantable neural interfaces can be used to connect human brains to artificial electronic circuits allowing e.g. control of computers by thoughts or treatment of various injuries and illnesses. An example of such is the possibility of treating spinal cord injuries by bypassing the damaged neural connection and allowing control of artificial limbs. This is achieved by inserting electrodes into neural tissue connected to instrumentation circuits recording electronic potentials generated by active neurons and decoding their meaning. While past solutions typically relied on recording of extracellular action potentials (EAPs), also known as neural spikes, generated by single neurons, the aim of this project is to focus on acquisition and processing of local field potentials (LFPs). This is as EAP-recording implants are typically hindered by limited lifetime due to the host body's foreign body response leading to scar tissue growth acting as a spatial and frequential low-pass filter, hence limiting the fidelity of recorded high-frequency EAPs. The low-frequency nature of LFPs allows for a significant reduction of the effect scar-tissue growth has on the recording.Some of the involved challenges include selection of electrode material. This has to ensure minimal added thermal noise within the frequency band of LFPs when in contact with cerebrospinal fluid while at the same time being chemically inert and medically harmless. Preliminary results have shown Niobium (Nb) as a promising material suitable for such a recording as it is known to be biologically inert and is commonly used e.g. in dental implants. Its polarizability leads to generally smaller noise power densities in LFP frequency bands than commonly used platinum and tungsten making it a suitable candidate material for neural recordings. This is to be investigated by direct noise measurements in electrolytes and subsequently verified by direct in-vivo measurements.Another challenge lies in the development of acquisition electronics which is greatly constrained by limits imposed on their power consumption governed by safety limits of heat dissipation in neural tissue on the order of 80 mW/cm^2. One of the techniques allowing reduction of used energy is clock-less, also known as continuous-time (CT), acquisition of signals. This approach leads to activity-dependent circuits that only use energy when activity is detected at their input. One of the aims of this project is to investigate the suitability and possible advantages of such circuits for acquisition of LFPs. As properties of such acquisition and sampling processes remain to a large extent unknown, mathematical simulations are used for their investigation. This is complemented by design of integrated circuits and practical measurements verifying hypotheses arising from theoretical models. This has already led to formulation of a minimal requirement to be satisfied in order to prevent aliasing similar to the Nyquist theorem which applies to ordinary sampling. In addition a novel method allowing reduction of flicker noise in CT sampling has been proposed and theoretically validated. An integrated circuit verifying this theory is to be designed, manufactured and tested.This work is part of the ENGINI project with an aim to design the next generation of neural implants that achieve superior chronicity by being completely wireless, minimal in size, targeting LFP recordings and allowing formation of distributed implant networks.The research aligns with the following EPSRC Research Areas: Assistive technology, rehabilitation and musculoskeletal biomechanics; Microelectronic device technology

植入式神经接口可用于将人脑与人工电子电路连接起来，例如通过思想控制计算机或治疗各种伤害和疾病。这样的一个例子是通过绕过受损的神经连接并允许控制假肢来治疗脊髓损伤的可能性。这是通过将电极插入与仪器电路相连的神经组织中来实现的，记录活动神经元产生的电子电位并解码其含义。虽然过去的解决方案通常依赖于记录单个神经元产生的细胞外动作电位（eap），也称为神经峰值，但该项目的目的是关注局部场电位（lfp）的获取和处理。这是因为eap记录植入物通常受到有限寿命的阻碍，这是由于宿主体的异物反应导致疤痕组织生长作为空间和频率低通滤波器，从而限制了记录高频eap的保真度。lfp的低频特性允许显著减少疤痕组织生长对记录的影响。所涉及的一些挑战包括电极材料的选择。这必须确保与脑脊液接触时lfp频带内最小的附加热噪声，同时保持化学惰性和医学无害。初步结果表明铌（Nb）是一种很有前途的材料，适合于这种记录，因为它已知是生物惰性的，通常用于牙科植入物。与常用的铂和钨相比，它的极化性导致LFP频段的噪声功率密度通常更小，使其成为神经记录的合适候选材料。这将通过直接测量电解质中的噪声来研究，随后通过直接体内测量来验证。另一个挑战在于采集电子产品的发展，这在很大程度上受到其功耗限制的限制，这些限制由神经组织散热的安全限制控制，约为80 mW/cm^2。其中一种可以减少使用能量的技术是无时钟，也称为连续时间（CT）信号采集。这种方法导致了依赖于活动的电路，只有当在其输入处检测到活动时才使用能量。该项目的目的之一是研究这种电路用于获取lfp的适用性和可能的优势。由于这种采集和采样过程的性质在很大程度上仍然未知，因此使用数学模拟进行调查。这是由集成电路的设计和实际测量验证理论模型产生的假设补充。这已经导致了为了防止混叠而必须满足的最小要求的表述，类似于适用于普通抽样的奈奎斯特定理。此外，还提出了一种降低CT采样中闪烁噪声的新方法，并进行了理论验证。一个集成电路验证这一理论是设计，制造和测试。这项工作是ENGINI项目的一部分，其目的是设计下一代神经植入物，通过完全无线、最小尺寸、针对LFP记录和允许形成分布式植入物网络来实现卓越的慢性。该研究与以下EPSRC研究领域相一致：辅助技术，康复和肌肉骨骼生物力学；微电子器件技术