【作者】 刘俊；

【导师】 孙永红； 郑筱祥；

【作者基本信息】 浙江大学 ， 生物医学工程， 2010， 硕士

【摘要】 脑机接口技术研究已经成为神经工程领域的热点和前沿问题,该研究有助于重建残障人士的运动和感觉功能,并推动神经科学和信息科学的发展。植入式电极技术能提供高质量的神经信号,相对非植入式来说更能提高脑机接口系统的性能。为建立植入式脑机接口,本文主要研究大鼠运动皮层神经解码的相关实验和硬件系统。为研究大鼠运动皮层神经解码,本文设计了大鼠前肢压杆获得给水奖赏的实验方案和硬件系统。硬件系统包括16通道微金属丝电极阵列、前端Headstage,压杆给水装置、神经元集群与压杆信号的同步记录和现场可编辑门阵列(FPGA)的硬件解码模块。结果显示,可以利用大鼠运动皮层的神经信号预测压杆的压力,大鼠能学会不压杆直接神经控制外部给水装置,同时本文在FPGA上实现的概率神经网络解码算法的计算时间仅为通用计算机上Matlab程序的四十分之一左右。为研究皮层微电流刺激对大鼠运动行为的影响,本文还设计了可用于自由活动状态下大鼠实验的电刺激系统,研究了内侧前脑束(MFB)电刺激对大鼠行为的影响。结果显示,MFB电刺激频率越快,大鼠运动越活跃,并且单侧的MFB电刺激引起大鼠对侧肢体运动的幅度比同侧大。这个实验的初步探索将利于进一步研究植入式脑机接口中的电刺激反馈技术。本文的创新性在于提出并实现了一种基于概率神经网络和FPGA的硬件解码方法,神经网络的训练样本存储在块RAM中,数学运算使用了Xilinx公司Virtex-5系列芯片中的DSP48E单元,指数激活函数通过泰勒级数和查找表近似。基于FPGA的实时神经信号处理技术的研究将有助于植入式脑机接口的进一步实用化。更多还原

【Abstract】 Brain-computer interface research has become a hot field of neural engineering. The research could help the disabled to restore their motor and sensory function, and promote the development of neuroscience and information science. Implanted electrode technology can provide high-quality neural signals and thus the potential for increased performance relative to non-invasive approaches. The main purpose of this thesis is to study the hardware system for motor cortex neural decoding experiments in rats to build an implantable brain-computer interface.In order to study motor cortex neural decoding, a hardware system was designed for rats performing a lever-pressing task for water rewards. The hardware system consists of a chronic 16-channel microelectrode array, a headstage, a water supply installation, a neural signal and lever pressure synchronous recording module and a FPGA-based neural decoding module. The results of this experiment indicate that neural signals from rat motor coetex can be used to predicte the lever pressure, and rats can learn to control an external water supply installation directly only using their brain. The results of FPGA-based decoding algorithm are as accurate as the realisation of Matlab, but the running speed is about 40 times faster.A portable telemetry system for brain stimulation was designed to study the influence of MFB electrical stimulation in free behaving rats. The results indicate two conclusions:the first is that the electrical stimulation of MFB initiattes and motivates forward locomotion, and the other is that it also causes different leves of activation between bilateral limbs. The exploration of this experiment will be beneficial to study electrical stimulation feedback technique in implantable brain-computer interface.The originality of this thesis is proposing and realizing a FPGA-based probabilistic neural network method for motor cortical neural decoding. In the FPGA architecture, training data of the network were stored in random access memory (RAM) blocks and multiply-add operations were realised by on-chip DSP48E slices. In the approximation of the activation function, a Taylor series and a look-up table (LUT) are used to achieve an accurate approximation. FPGA-based real-time neural signal processing technology research will contribute to practical use of implanted brain-computer interfaces.更多还原