ERI: Memristor-based Neuromorphic Circuit Design for Closed-Loop Deep Brain Stimulation

帕金森氏症（PD）是一种脑部疾病，每年影响全球数百万患者。PD患者会出现运动症状，包括不受控制的颤抖或肌肉僵硬，可能会感到紧张和难以移动。脑深部电刺激（DBS）是治疗帕金森病运动症状的有效方法。DBS是一种外科手术，在胸部放置一个信号发生器，将电脉冲发送到大脑的特定区域。这些来自信号发生器的电脉冲通过影响大脑中的细胞来控制运动症状。DBS系统可以改变患者的生活，但持续而僵硬的电脉冲会产生不必要的副作用，比如可能阻塞血液流动。最近，科学家们开发出了一种新的DBS系统，称为闭环DBS (CL-DBS)，该系统可以根据PD的症状向大脑发送各种电脉冲，以避免副作用。CL-DBS系统面临的一个挑战是，它需要一台功能强大的计算机来产生预期的各种电脉冲。然而，这些功能强大的计算机由于体积过大而无法放置在患者的胸部。为了解决这个问题，这个项目旨在设计一种叫做神经形态芯片的新型计算机。该芯片通过使用小尖峰信号进行计算，模拟人类大脑，实现高能效。这种新的神经形态芯片将使CL-DBS更智能、更小、更轻，极大地造福所有PD患者。该项目为来自密歇根州上半岛铜国地区的大学生和高中生提供了一个独特的机会，让他们参与神经科学、帕金森病、大脑康复、人工智能和微芯片设计等跨学科研究。该项目旨在设计一种神经形态的CL-DBS芯片，该芯片由电子神经元和记忆突触组成，能够适应用户症状，同时大幅降低功耗和设备尺寸。PD症状的严重程度可以通过大脑的β振荡来判断。在闭环系统的前馈和反馈分支处放置两个spike Neural Networks (SNN)，识别PD症状并产生相应的刺激信号。这些snn中的神经元和突触将使用互补金属氧化物半导体（CMOS）技术和忆阻器实现。该项目将集中在两个任务上：(1)记忆突触设计；(2)电子神经元设计。此外，外围电路，包括带通滤波器，低噪声放大器和读/写电路，将被开发。该芯片将被录下来进行进一步评估，通过将其与使用不同计算硬件的其他CL-DBS系统进行比较，包括图形处理单元（gpu）和现场可编程门阵列（fpga），基于1)功耗；2)响应时间；3)芯片面积。神经形态医疗芯片的研究将大大有利于节能和智能植入式医疗设备的发展，减少其尺寸、重量和能量预算，同时使其更具智能和适应性。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Parkinson's disease (PD) is a brain disorder affecting millions of patients worldwide each year. PD patients experience motor symptoms including uncontrolled shaking or rigid muscles that may feel tight and difficult to move. Deep brain stimulation (DBS) is an effective therapy used to treat motor symptoms of PD. DBS is a surgical procedure that involves placing a signal generator in the chest to send electrical pulses to a specific region of the brain. These electrical pulses from the signal generator control motor symptoms by affecting the cells in the brain. The DBS system is life-changing for patients, but the continuous and rigid electrical pulses cause unwanted side effects, such as potentially blocking blood flow. Recently, scientists have developed a new DBS system called Closed-Loop DBS (CL-DBS) where the generator can send various electrical pulses back to the brain depending on PD symptoms to avoid side effects. One challenge for a CL-DBS system is it requires a powerful computer to generate the expected and various electrical pulses. However, these powerful computers cannot be placed in the chest of patients due to their large size. To solve this issue, this project aims to design a new type of computer called a neuromorphic chip. This chip mimics human brains by using small spiking signals for calculations to realize high energy efficiency. This new neuromorphic chip will make CL-DBS smarter, smaller, and lighter, greatly benefiting all PD patients. The project provides a unique opportunity for college and high school students from the Copper Country region in the Upper Peninsula of Michigan to participate in interdisciplinary research on neuroscience, Parkinson’s disease, brain rehabilitation, artificial intelligence, and microchip design. The project aims to design a neuromorphic CL-DBS chip consisting of electronic neurons and memristive synapses that adapts to user symptoms while substantially lowering power consumption and device size. The severity of PD symptoms is indicated by beta oscillations from the brain. Two Spiking Neural Networks (SNN) will be placed at the feedforward and feedback branches of the closed-loop system to recognize PD symptoms and generate stimulation signals accordingly. The neurons and synapses in these SNNs will be implemented using complementary metal-oxide semiconductor (CMOS) technology and memristors. The project will focus on two tasks: (1) memristive synapse design; and (2) electronic neuron design. Additionally, peripheral circuitries, including bandpass filters, low-noise amplifiers, and reading/writing circuits, will be developed. The chip will be taped out for further evaluation by comparing it with other CL-DBS systems using different computational hardware, including Graphics Processing Units (GPUs) and Field Programmable Gate Arrays (FPGAs), based on 1) power consumption; 2) response time; 3) chip area. This research on neuromorphic medical chips will significantly benefit the development of energy-efficient and smart implantable medical devices by reducing their size, weight, and energy budget while making them more intelligent and adaptive.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.