| Currently, deep brain stimulation (DBS) is considered as one of the most effective ways to treat brain diseases, such as epilepsy, Parkinson disease and so on. In order to further explore the mechanism of DBS and figure out more effective stimulus parameters, high-performance electrical stimulator are requird. However, traditional electrical stimulator cannot generate complex waveforms and the adjustable range of parameters is not flexible enough. To some extent, these factors have hindered the further study of DBS.In order to solve this problem, we designed a multi-functional neural stimulation system, it was controlled by a LabVIEW software which was responsible for generating complex user-defined stimulation waveforms and driving the data acquisition (DAQ) card to control electrical stimulator. In addition, several kinds of stimulis were designed to investigate the effect of them on the excitability of neurons in CA1 region of rat hippocampal. The main results were summarized as follows:(1) The control software of the neural stimulation system was based on LabVIEW. Test results showed that, the user interface was simple and beautiful and it was real-time, scalable and general. It also can drive the DAQ card for accurate input and output. Users can use and modify the program easily to meet their special needs.(2) Monophasic and biphasic pulses with same polarity were generated by the system and were respectively applied in the hippocampus CA1 region of anaesthetized rats. Responses of neuronal populations in the CA1 region were examined to quantitatively analyze the effect of different stimulation waveforms. The results showed that:During 100 Hz high-frequency antidromic stimulations on the efferent fibers of CA1 region, in the 0.5 s period at the beginning of stimulation, the amplitude suppression of population spikes induced by monophasic pulses was 54.2±21.3% and was significantly higher than that induced by biphasic pulses 39.0± 10.2%. It indicated that the effect of monophasic pulses was much stronger than that of biphasic pulses during high-frequency stimulations. However, trains of high-frequency monophasic pulses tend to cause damages to neuronal tissues.(3) Three special types of high frequency stimulation (HFS) were designed and were applied to the deep brain stimulation to examine their effects on axonal block, including intensity-linearly-increasing HFS, frequency-changing HFS and discontinuous HFS with regular pauses. Experiments in the efferent fibers of the hippocampus CA1 region in rats showed that, the response of neurons in CA1 region to these three types of HFS are different from that to the traditional HFS:the intensity-linearly-increasing HFS could induce axonal conduction block and avoid population spike with large amplitude as well; during frequency-changing HFS, the degree of axonal block enhanced with increasing frequency; under the discontinuous HFS, the blocked axons could recover in a time interval, but the degree of recovery might be associated with the length of the pause.In conclusion, the multi-functional neural stimulation system we developed can design and output various stimulus waveforms according to the needs of users. The system has high output accuracy and versatility and it can provide convenience for the electrophysiological experiments. The experimental test results showed that, the stimulation effect of monophasic pulses was significantly stronger than the effect of biphasic pulses with the same polarity. In addition, three special stimulus we designed have certain research value, which may provide a new way for the study of deep brain stimulation. These results are important for the further understanding of DBS mechanisms and for the efficiency and safety of wide applications of DBS in clinic. |
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