用于脊髓神经功能定位的刺激波形分析

目的:找出能减小电荷积累和组织损伤的刺激波形。方法:先定义一个双极性矩形脉冲对大鼠的脊髓进行刺激,然后将该波形改为阶梯波形并在相同的位置进行刺激,比较在活体大鼠中阶梯波形和双极性矩形脉冲对刺激阈值的影响以及电荷量的关系。结果:在一阶阶梯刺激波形条件下,尽管刺激阈值V会随着负脉冲宽度T1的增加而增加,但一阶阶梯刺激波形的电荷总量都低于双极性矩形脉冲的电荷总量。增加阶梯数目i也会导致刺激阈值的增加,但阶梯数目1相似文献   

多通道经颅交流电刺激仪的设计

目的:电信号不同,对生物进行电刺激产生的生物效应也不相同。医疗领域已经研究出了许多有效成熟的电刺激治疗模式,市场上已有很多具有简单模式的电刺激仪,它们一般都只有特定的治疗模式,功能比较单一。为了满足多模式联合治疗和医学实验的需要,我们研发了一款具有多种治疗模式的交流电刺激仪。方法:该交流经颅电刺激仪选用TI的低功耗MSP430F413单片机作为主控芯片,控制以MAX038作为信号发生芯片的波形发生电路。因为MAX038能够产生0.1 Hz-20 MHz可调的正弦波、方波、三角波,可以实现两个独立控制波形的耦合输出,因此能够形成多种刺激模式。通过软件编程,使该电刺激仪具有丰富的参数设置与显示功能。结果:研制出的电刺激仪具有内置多种常用治疗模式(其中有2个为多治疗模式定时自动转换的可循环模式),利用6个中断按键作为控制键,可以方便快捷地进行模式选择和参数设置。通过配备不同的电极,可以进行电流与电场治疗模式切换:导电电极用于电流治疗,绝缘电极用于电场治疗。结论:经过多次调试和验证,该电刺激仪的输出电压Vp-p为5 V,可按需要外接医用功率放大设备进行放大,输出频率可调范围为0.1 Hz-5 MHz,调节精度为±2%,可以输出噪声较低的方波,三角波,正弦波及其调制波形,具有良好的稳定性和可靠性,同时满足国际电工委员会颁布的医疗设备安全标准,达到了最初的设计要求。     

用于超短波理疗仪的人体阻抗高频信号检波电路设计

本电路是用于超短波理疗设备的人体阻抗自动调谐装置。为了判断能量发射电路与加载人体组织后的接收电路之间谐振参数是否达到最佳匹配状态,本文设计了针对高频信号的包络检波电路,配合接收电路中可变电容自动调节装置,完成阻抗匹配与调谐功能。研究通过采样线圈接收到的调幅波信号,将检波处理后的电压信号与能量发射电路中电流信号进行比对。实验显示,本电路检波处理后的电压信号波形稳定,可被低速模拟数字转换芯片(ADC)识别,且与能量发射电路电流信号正相关。检波处理后的电压值可真实表现电路谐振状态,实现人体阻抗信号采集功能。     

基于2^n伪随机复合频率信号的神经肌肉电刺激系统设计

目的：每一块肌肉都是由众多肌纤维组成,每一组肌纤维的固有频率不同,在对肌肉进行电刺激时,使用单一频率的电刺激不能满足同时对多组肌纤维进行刺激,不能达到最有效的电刺激作用,因此我们设计了一种基于伪随机信号的复合频率电刺激仪,能在一个刺激周期内实现多个频率的电刺激。方法：设计了一个以STC12C5410AD单片机为核心控制芯片的伪随机信号神经肌肉电刺激仪系统,采用串口实现上下位机的通讯,通过软件编程,上位机发送主频数、主频频率、间歇时间和刺激时间各项参数指令,由单片机控制输出两路伪随机脉冲信号,并通过逆变电路实现伪随机信号的输出,在逆变电路中加入电流监测电阻,实时监测输出信号的电流大小,将其控制在人体安全电流10mA以下,保证了用户的使用安全。结果：研制出的电刺激仪能产生1kHz以下多种主频信号的复合,根据主频数和主频频率的不同输出不同的复合频率信号,同时对输出电流的检测,验证了信号的安全性。结论：本文将伪随机复合频率信号运用于肌肉电刺激仪中,取代传统的单一频率电刺激仪,实现了技术上和理论上的创新,具有较高的临床实验和科研价值。     

双向脉冲可实现的神经纤维选择性兴奋

背景：研究证明利用电刺激外周神经纤维可恢复一些因失去中枢神经控制的肌肉的功能。 目的：验证双电极1 mm较近距离下双向方波脉冲实现神经选择性兴奋的正确性,并基于此实现神经的选择性兴奋。 方法：成年Wistar大鼠8只,麻醉后暴露大鼠坐骨神经,将电极小心放于坐骨神经干,建立神经选择性刺激模型。实验用电极为自制Cuff双极性电极,刺激器采用的是Grass S88刺激器和AWG2005任意波形信号发生器。采取双电极双向刺激方式,两个电极之间距离为1 mm,刺激波形选用脉宽为0.2 ms的对称双向脉冲,其输出脉冲的幅度、脉宽和延时均可调。调节刺激强度,研究双电极双向刺激下神经兴奋性的规律,以此实现神经的选择性兴奋,并利用“碰撞法”原理验证利用双电极双向刺激方法实现神经选择性兴奋的可行性。 结果与结论：实验过程中神经动作电位的变化将经P511放大器放大后接入示波器显示,双电极刺激波形为脉宽为0.2 ms的对称双向脉冲。随着刺激幅度的增大,实现神经的选择性兴奋。说明用距离很近(1 mm)的双电极双向对称脉冲的方法实现了神经的选择性兴奋,并利用“碰撞法”原理证实了此种方法的有效性和可行性。     

多参数经皮神经肌肉电刺激仪的设计

目的：电刺激仪器是通过电流作用于目标组织，使目标组织产生相应的功能变化。刺激方式、刺激电流、波形等均会影响治疗效果。市面上现有的神经肌肉电刺激仪一般只有单一的治疗模式，局限性很大。为了有针对性地治疗不同肌肉疾病，我们设计了一个能够方便准确地控制刺激电流的多参数经皮神经肌肉电刺激仪系统：方法：设计了一个以STC12C5410AD单片机为核心控制芯片的多参数经皮神经肌肉电刺激仪系统，采用串口实现上下位机的通讯，通过软件编程，上位机发送波形、频率、脉宽、间隙时间、最大刺激电流等各项参数指令，由单片机控制D／A转换芯片DAC8532输出指定波形，经过高压开关保护电路加入恒流源电路，产生恒定的电流对目标组织进行刺激。系统加入多项安全控制措施，有效地避免了实际操作过程中的安全隐患；结果：通过对系统进行电阻测试，验证了系统为恒流型仪器，经过电阻的刺激电流由且仅由输入信号的各项参数确定，与电阻的大小无关。由临床试验证明了通过改变参数，可以改变刺激模式，并验证了该系统的安全性和有效性。结论：该系统能设置成临床上使用的经皮电神经刺激疗法的各种模式。安全有效，有利于临床实验和相关科研的开展。     

压力传感器信号调理电路设计

详细介绍了循环式氦氧混合气辅助呼吸装置压力传感器信号调理电路传感器接入、电流源、差分放大器、输出放大器、非线性调整环、频率响应等功能模块的设计,明确给出了信号调理电路差分放大器及零点调整电路中电阻的计算方法.测试结果表明:该压力传感器信号调理电路在实现大电压信号满量程输出、输出电压与输入压力保持线性关系、零点电压提升等功能方面取得了很好的效果.     

基于混沌信号的经皮神经电刺激仪的设计

传统的电刺激仪器都是采用三角波、方波与非对称波等信号作为刺激信号源,或是将一些特定的信号先进行存储、然后再输出作为信号源,这些信号都呈现出周期性,作用于人体时容易使人产生适应性,随着刺激次数的增多而使效果逐渐变差,论文设计了一个基于混沌模型的非周期信号的电刺激系统。首先是在MATLAB软件的Simulink平台下构建出混沌模型,然后借助于DSP Builder软件将混沌模型转换为FPGA的工程文件,通过Simulink平台的模型仿真及Modelsim软件的行为级仿真,仿真无误后将工程文件在Altera公司的开发平台Quartus软件下进行编译、综合,最后生成可执行文件,下载到FPGA芯片即产生了混沌信号;将信号进行电压放大,功率放大,接入电极,实现了基于混沌信号的电刺激系统。所设计的系统获得了新型的电刺激效果,通过改变混沌方程的参数以及改变信号的输出频率,可以改变刺激时的直观感觉,由于人体的生物信号本身具有复杂的混沌特性,用它作用于人体所具有的更深层次的生物效应还需更多的探索研究。     

循环式氦氧混合气辅助呼吸装置的设计

概括了循环式氦氧混合气辅助呼吸装置的工作原理、气路结构,详细介绍了硬件电路设计、氧浓度控制算法及系统工作流程,并给出了由MATLAB软件所得到的系统的阶跃响应.测试和仿真结果表明:系统的硬件电路在实现大电压信号满量程输出、输出电压与输入压力保持线性关系、零点电压提升等功能方面有良好的性能;氧浓度控制算法在保持系统稳定、减少系统震荡和冲击等方面取得了较好的效果.     

基于按摩的电刺激器的设计

目的设计一种基于中医按摩的电刺激仪器——将产生的电刺激信号通过中医的按摩手法给患者按摩。方法研究采用STC89C58RD+单片机作为控制器,采用LCD点阵液晶显示作为可视化的提示工具,采用4*4矩阵键盘作为输入控制接口,采用变压器作为电刺激信号升压器件。结果研究实现了预期目标,用户可通过LCD提示输入控制点刺激信号强度的按键,单片机处理后输出相应的脉冲波形,进而触发生成用于按摩的电刺激信号。结论对51单片机开发应用,实现了输入不同的频率信息,产生不同强度的电刺激信号,使人感觉不同程度的麻刺激,能够用于治疗和保健。     

Battery powered neuromuscular stimulator circuit for use during simultaneous recording of myoelectric signals

Surface Functional Electrical Stimulation (FES) requires high stimulation voltages. A step-up transformer in the output stage of the stimulation circuit is often used. In the present technical paper a voltage controlled current source (VCCS) is presented as an alternative to the transformer coupling. Two (master–slave) coupled transconductance amplifiers (TAs)—in series with pre-charged capacitors—are used to drive the output current. After each stimulation pulse the capacitors are recharged to a high voltage by a switch mode power supply (SMPS). A multiplexer in the output stage is used to provide biphasic output. Output rise-time (10–90%) was less than 2 μs at 100 mA output. Biphasic charge balanced stimulation current can be produced with a net current to ground of less than 20 nA, thus virtually separated from ground. The circuit permits recording of the volitional myoelectric signal from the stimulated muscle. It is part of a portable myoelectrically controlled FES system powered by 2 AA batteries and currently used in clinical trials.     

医用核素活度计的设计与改进

目的对基于LabVIEW的医用放射性核素活度计的系统设计方案进行了硬件部分的改进。方法应用性能优良的电压／频率转换芯片VFC32实现了硬件电路设计和性能分析。利用设计的电路对医用放射性核素活度计电离室输出的电压进行信号处理,得到的频率信号通过NI公司的USB-6009 DAQ和LabVIEW8．0开发的虚拟仪器实现进一步的处理和显示。结果实验数据的图形表明改进后的系统在中低频段具有更好的线性度。结论改进后的活度计更有利于改善医用放射性核素活度计的测量精度、测量范围、低能探测限等性能。     

Parallel processing in retinal ganglion cells: how integration of space-time patterns of excitation and inhibition form the spiking output

Our goal was to understand how patterns of excitation and inhibition, interacting across arrays of ganglion cells in space and time, generate the spiking output pattern for each ganglion cell type. We presented the retina with a 1-s flashed square, 600 microm on a side, and measured patterns of excitation and inhibition over an 1,800-microm-wide region encompassing many ganglion cells. Excitatory patterns of on ganglion cells resembled rectified versions of the voltage patterns of on bipolar cells. Inhibitory patterns in on ganglion cells resembled the rectified versions of voltage patterns of off bipolar cells. off ganglion cells received off excitation and on inhibition. Many ganglion cells also received an additional wide field transient inhibition derived from the activity of both on and off bipolar cells. Ganglion cell spiking was suppressed in those space-time regions dominated by inhibition. We classified each ganglion cell type by correlating its space-time patterns with its dendritic morphology. These studies suggest the bipolar and amacrine cell circuitry underlying the interplay between on and off signals that generate spiking patterns in ganglion cells. They reveal a surprising synergistic interaction between excitation and inhibition in most ganglion cells.     

剩余电压检测的关键技术研究

剩余电压是指用插头连接电源的设备在拔掉插头的瞬时,由设备内部的储能元件产生的存在于插头上各插脚之间的残余电压。若人体触摸到插头且该电压大于某一限值,就会产生触电危险。制定剩余电压、剩余能量的限值是为了保护患者、操作者或其他人员的人身安全,防止在断电瞬间触及带电部件而发生危险。故准确地检测医疗设备的剩余电压值具有十分重要的意义。本文解决了剩余电压测量的一个关键技术问题,即设计一个零电位检测的关键电路,与可调延时设计配合能使设备在交流峰值处准确断电。这种峰值时刻断电检测系统,用于一种单片机控制的新型剩余电压测量装置,该装置将具有较好的重复性、稳定性,以克服现有的剩余电压测试仪器不能准确地在峰值处断电、测试重复性差等缺陷。该检测电路结构简单,性能稳定,能够在整流波过零的时刻可靠地产生宽度很窄的触发脉冲。采用可调延时设计,能够解决元器件带来的时延。     

Estimating use-dependent synaptic gain in autonomic ganglia by computational simulation and dynamic-clamp analysis

Biological gain mechanisms regulate the sensitivity and dynamics of signaling pathways at the systemic, cellular, and molecular levels. In the sympathetic nervous system, gain in sensory-motor feedback loops is essential for homeostatic regulation of blood pressure and body temperature. This study shows how synaptic convergence and plasticity can interact to generate synaptic gain in autonomic ganglia and thereby enhance homeostatic control. Using a conductance-based computational model of an idealized sympathetic neuron, we simulated the postganglionic response to noisy patterns of presynaptic activity and found that a threefold amplification in postsynaptic spike output can arise in ganglia, depending on the number and strength of nicotinic synapses, the presynaptic firing rate, the extent of presynaptic facilitation, and the expression of muscarinic and peptidergic excitation. The simulations also showed that postsynaptic refractory periods serve to limit synaptic gain and alter postsynaptic spike timing. Synaptic gain was measured by stimulating dissociated bullfrog sympathetic neurons with 1-10 virtual synapses using a dynamic clamp. As in simulations, the threshold synaptic conductance for nicotinic excitation of firing was typically 10-15 nS, and synaptic gain increased with higher levels of nicotinic convergence. Unlike the model, gain in neurons sometimes declined during stimulation. This postsynaptic effect was partially blocked by 10 microM Cd2+, which inhibits voltage-dependent calcium currents. These results support a general model in which the circuit variations observed in parasympathetic and sympathetic ganglia, as well as other neural relays, can enable functional subsets of neurons to behave either as 1:1 relays, variable amplifiers, or switches.     

Noise characteristic design of CMOS source follower and voltage amplifier for active semiconductor microelectrodes for neural signal recording

A noise performance design method for the pre-amplifiers of an active neural probe is given. The on-chip circuitry of the active neural probe consists of CMOS devices that show high-/ low-frequency noise, so that the device noise can become dominant. Analysis of the signal-to-device-noise ratio (SDNR) for the CMOS source follower buffer and two-stage differential voltage amplifier is given. Closed-form expressions for the output noise power are derived and exploited to tailor the parameters that are controllable during circuit design. The output SDNR is calculated considering the real extracellular action potentials, the electrode-electrolyte interface and the noise spectrum of CMOS devices from typical foundries. It is shown that the output device noise power can be much higher than the output signal power if the devices at the input stage of the pre-amplifier are made as small as given fabrication technology permits. Quantitative information of the circuit parameters to achieve an SDNR higher than 5 for neural spikes with 60μV amplitude are provided for both preamplifier types.     

Synaptic pathways that shape the excitatory drive in an OFF retinal ganglion cell

Different types of retinal ganglion cells represent distinct spatiotemporal filters that respond selectively to specific features in the visual input. Much about the circuitry and synaptic mechanisms that underlie such specificity remains to be determined. This study examines how N-methyl-d-aspartate (NMDA) receptor signaling combines with other excitatory and inhibitory mechanisms to shape the output of small-field OFF brisk-sustained ganglion cells (OFF-BSGCs) in the rabbit retina. We used voltage clamp to separately resolve NMDA, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), and inhibitory inputs elicited by stimulation of the receptive field center. Three converging circuits were identified. First is a direct glutamatergic input, arising from OFF cone bipolar cells (CBCs), which is mediated by synaptic NMDA and AMPA receptors. The NMDA input was saturated at 10% contrast, whereas the AMPA input increased monotonically up to 60% contrast. We propose that NMDA inputs selectively enhance sensitivity to low contrasts. The OFF bipolar cells, mediating this direct excitatory input, express dendritic kainate (KA) receptors, which are resistant to the nonselective AMPA/KA receptor antagonist, 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide disodium salt (NBQX), but are suppressed by a GluK1- and GluK3-selective antagonist, (S)-1-(2-amino-2-carboxyethyl)-3-(2-carboxy-thiophene-3-yl-methyl)-5-methylpyrimidine-2,4-dione (UBP-310). The second circuit entails glycinergic crossover inhibition, arising from ON-CBCs and mediated by AII amacrine cells, which modulate glutamate release from the OFF-CBC terminals. The third circuit also comprises glycinergic crossover inhibition, which is driven by the ON pathway; however, this inhibition impinges directly on the OFF-BSGCs and is mediated by an unknown glycinergic amacrine cell that expresses AMPA but not KA receptors.     

握速可调式肌电假手的系统研究

针对假手无法根据使用者的意愿来控制其握合速度的问题,设计了一种握速可调的智能肌电假手。在该肌电假手系统中,电极引入的表面肌电信号,放大150倍后,在频域进行信号处理。经过阈值和等值计算,最终输出控制信号到驱动电路对假手的直流微电机进行控制。10名受试者参加了抓握试验,每人重复5次,记录输入肌电信号强度为500、1 000、1 500 mV时的输出电流、输出电压和握力等值,并拟合假手输出电压、输出电流、握力与输入肌电信号大小的曲线。拟合结果表明,假手速度与输出电压成正相关,在带有负载且不过载时,握力随着输出电流增大而增大。本假手系统具有稳定性,同时和假手握速可通过检测到的肌电信号强弱进行调节,提高了假手的灵活性。     

一种用于神经刺激研究的触屏控制小型超声发生器

超声发生器是研究超声刺激的重要工具,但是目前并无可供选择的专用设备。目前实验室所用超声发生器通常都用多台通用仪器搭建而成,体积大,操作复杂。本文设计了一种用于神经刺激研究的小型超声发生器,用触屏作为控制界面,方便刺激参数的输入和修改;独立的E类末级功放非常小巧,可接近换能器放置,换能器的电抗参数纳入功放从而省去了匹配电路,整机体积进一步缩小。内置的现场可编程门阵列（FPGA）产生脉冲方波,经专门的驱动电路后控制E类功放中MOSFET的通断。测试表明,本文设计的超声发生器产生的波形准确,最高频率可达2 MHz。配接自制的500 kHz换能器,在30 V电源电压下输出功率6.23 W,最大声压达到168.3 kPa,并且还有可提升的空间。该发生器体积小,操作方便,电路设计简单,适用于超声神经刺激的研究。     

模型动物失神经支配及神经肌肉电刺激的可编程植入式神经肌肉电刺激器

背景：植入式神经肌肉电刺激器可用于研究功能性电刺激对动物失神经肌肉的作用机制,但体积偏大,功能单一。 目的：设计一种微型、参数可调的植入式神经肌肉电刺激器。 方法：基于红外通信技术,以MSP430为控制核心,采用低功耗设计,经体外控制器设置参数,产生电荷平衡的双相脉冲序列,可对神经或肌肉进行电刺激。 结果与结论：实验设计的刺激器可在体编程,能够灵活设置刺激电压幅值、频率、脉宽和间隔时间等参数。多参数的设置丰富了刺激协议选择性,可最小化对目标神经肌肉临近组织的不可预测刺激,优化了功耗设计,可确保实验动物的安全性。