Centre for Bio-Inspired Technology, Imperial College London , London, SW7 2AZ, United Kingdom. Department of Electrical and Electronic Engineering, Imperial College London, London, SW7 2BT, United Kingdom. Care Research & Technology Centre, UK Dementia Research Institute at Imperial College London, London, United Kingdom. Author to whom any correspondence should be addressed.
J Neural Eng. 2020 Jul 10;17(4):046013. doi: 10.1088/1741-2552/ab947a.
This paper describes the design, testing and use of a novel multichannel block-capable stimulator for acute neurophysiology experiments to study highly selective neural interfacing techniques. This paper demonstrates the stimulator's ability to excite and inhibit nerve activity in the rat sciatic nerve model concurrently using monophasic and biphasic nerve stimulation as well as high-frequency alternating current (HFAC).
The proposed stimulator uses a Howland Current Pump circuit as the main analogue stimulator element. 4 current output channels with a common return path were implemented on printed circuit board using Commercial Off-The-Shelf components. Programmable operation is carried out by an ARM Cortex-M4 Microcontroller on the Freescale freedom development platform (K64F).
This stimulator design achieves ± 10 mA of output current with ± 15 V of compliance and less than 6 µA of resolution using a quad-channel 12-bit external DAC, for four independently driven channels. This allows the stimulator to carry out both excitatory and inhibitory (HFAC block) stimulation. DC Output impedance is above 1 M Ω. Overall cost for materials i.e. PCB boards and electronic components is less than USD 450 or GBP 350 and device size is approximately 9 cm × 6 cm × 5 cm.
Experimental neurophysiology often requires significant investment in bulky equipment for specific stimulation requirements, especially when using HFAC block. Different stimulators have limited means of communicating with each other, making protocols more complicated. This device provides an effective solution for multi-channel stimulation and block of nerves, enabling studies on selective neural interfacing in acute scenarios with an affordable, portable and space-saving design for the laboratory. The stimulator can be further upgraded with additional modules to extend functionality while maintaining straightforward programming and integration of functions with one controller. Additionally, all source files including all code and PCB design files are freely available to the community to use and further develop.
本文描述了一种新型多通道可阻断刺激器的设计、测试和使用，该刺激器用于急性神经生理学实验，以研究高度选择性的神经接口技术。本文展示了该刺激器使用单相和双相神经刺激以及高频交流（HFAC）同时兴奋和抑制大鼠坐骨神经模型中神经活动的能力。
所提出的刺激器使用 Howland 电流泵电路作为主要模拟刺激器元件。使用商业现货（COTS）组件在印刷电路板上实现了 4 个具有公共返回路径的电流输出通道。通过 Freescale 自由开发平台（K64F）上的 ARM Cortex-M4 微控制器进行可编程操作。
该刺激器设计使用四路 12 位外部 DAC 实现了±10 mA 的输出电流、±15 V 的顺应性和小于 6 µA 的分辨率，为四个独立驱动的通道提供了±10 mA 的输出电流、±15 V 的顺应性和小于 6 µA 的分辨率。这使得刺激器能够进行兴奋和抑制（HFAC 阻断）刺激。直流输出阻抗大于 1 MΩ。材料的总成本，即 PCB 板和电子元件的成本，低于 450 美元或 350 英镑，设备尺寸约为 9 cm×6 cm×5 cm。
实验神经生理学通常需要为特定的刺激要求投资大量的设备，特别是在使用 HFAC 阻断时。不同的刺激器彼此之间进行通信的手段有限，这使得协议更加复杂。该设备为多通道刺激和神经阻断提供了有效的解决方案，为在急性情况下进行选择性神经接口研究提供了一种经济实惠、便携式且节省空间的实验室设计。该刺激器可以通过添加额外的模块进行进一步升级，以在保持简单编程和功能集成的同时扩展功能。此外，所有的源代码文件，包括所有的代码和 PCB 设计文件，都免费提供给社区使用和进一步开发。
