Design And Animal Experiment Of A Transcranial Direct Current Stimulator

Alzheimer’s disease(AD) is a neurodegenerative disorder with unknown causes, which is characterized by progressive loss of learning and memory, perception, judgment, language comprehension and movement. AD, currently affecting more and more people, has devastating effects on patients and their families, and even poses a tremendous socioeconomic impact on the society. However, there are no effective clinical treatments can permanently cure AD. Transcranial direct current stimulation(t DCS), on account of its outstanding advantages such as noninvasion, easy to realize, lower cost, safe and portability, along with great potentials in relieving the AD symptoms, has attracted more and more researchers’ attention in recent years.Aiming at satisfying the need of clinical researches and making up for the market blanks in t DCS, a kind of t DCS stimulator, which was based on FPGA, was developed. Choosing EP2C35F672C6 as the control unit and combining with VHDL programming, the stimulator can realize the real-time response of application for stimulation parameter settings, and then drive the corresponding modules to generate digital stimulation signal with adjustable intensity, frequency, period or pulse width, as well as optional stimulation waves. The conversion of digital signal into analog signal was realized by D/A conversion module. Then, the analog signal was processed with constant-current conversion. Finally, the stimulation current was applied to target region of the patients through surface electrodes. Furthermore, an additional function was bound to this stimulator so as to monitor electrode contact in real time. With the help of this stimulator, the experiment about application of t DCS in AD rat models was carried out successfully.Firstly, the challenges of curing AD were expound and a new potential approach was introduced. Based on the analysis of clinical results from studies of t DCS in AD patients and comparison with other two similar stimulators, design requirements of the system parameters were fixed on. Next, the hardware design of the stimulator was introduced in detail, including the power management module, human-computer interaction module, D/A conversion module, constant-current module, monitoring electrode contact module and so on. As to the software design of the stimulator, it was based on modularized method to mainly implement the waveform generating module, duration setting module, D/A conversion module, key reception and display module. After accomplishing the above designs, the stimulator was on the debugging, and the results showed that its stimulus parameters achieved the requirements expected. At last, in order to further verify if the stimulator implemented required performances, and investigate the behavioral and the histologic effects of t DCS on AD, anodal repetitive t DCS with different intensities was applied to AD rats’ right frontal cortex. Then t DCS-induced behavioral and histologic changes on learning and memory were evaluated and the possible mechanisms were discussed. Results indicated that the proposed repetitive anodal t DCS with 100 mA and 200 mA can repair the learning and the memory dysfunction of AD rats.