| New non-invasive,high-precision brain stimulation and modulation technology is hotspots and frontier in recent years.The development of this technology can provide new therapeutic treatments to the patients with cranial nerve diseases and has significance scientific research sense and clinical application value.In this thesis,we use static magnetic field and ultrasound act on the nervous tissue to generate an induced current,so as to activate or inhibit the activity of nerve tissue.As a new type of neural modulation method,it is called transcranial acousto-magnetic stimulation(TAMS).TAMS combines low-intensity focused ultrasound stimulation(LFUS)with transcranial magnetic stimulation(TMS),which not only has a higher spatial resolution but also reduces the intensity of ultrasound and improve the security.This work is supported by the Hebei Provincial Natural Science Foundations and the Hebei Provincial High-level Talent Project of China.We conduct theoretical analysis,platform design and experimental research to carry out the research work,which involves in many fields such as bioelectromagnetics and biomedicine.The main aspects of the work are listed as follows:1.This thesis introduces the research background,summarizes the principles of neural control technology and their advantages and disadvantages,The technical advantages,research status and urgent problems of transcranial magnetic coupling stimulation are described in detail.2.The basic theory of transcranial magnetic coupling stimulation was studied,and the generation principle of the induced electric field and the generation mechanism of the stimulating current were analyzed.The Chay model was used to simulate neuronal firing under TAMS stimulation.The results show,that the induced current influenced by TAMS can change the discharge rhythm of neurons.The attenuation and thermal effects of the ultrasound were calculated.The results show that attenuation of ultrasound in penetrating the cranial basic can be ignored,the thermal effect of ultrasound during stimulation is also small and does not cause thermal damage to the tissue.3.According to the modular design principle,the TAMS platform was constructed,which can provide hardware for the carrying out of TAMS experiments.The platform constructed in this paper mainly includes permanent magnet module,ultrasonic emission module and local field potential acquisition and analysis module.The magnetic field distribution of the permanent magnet was optimized,and manufactured,the magnetic flux density of the static magnetic field was measured,and the optimal stimulation area was selected;Ultrasonic emission module can generate ultrasonic beam with adjustable parameters,and the focusing lens was used to improve the focusing performance of the ultrasonic beam,so that it can stimulate the target area of SD(Sprague-Dawley)rats more accurately;local field potential acquisition and analysis module can be used to measure and process the nerve signals evoked by TAMS,with this platform,we can easily study the effect of acousto-magnetic coupling stimulation on brain nerve activity.The stimulation effects of different parameters were analyzed by the power spectrum of the local field potential(LFPs).4.Using the built TAMS hardware,we conducted the SD rat motor cortex stimulation experiment,and the feasibility of the coupling method and the effectiveness of the stimulation platform were verified.Through the use of different stimulus parameters,SD rats were observed in the limbs and tail movement,and the effective stimulus parameters of TAMS motor cortex were determined.The effects of anesthetic dose and coupling agent on the success rate of acupuncture stimulation and the safety of sports injury were studied.5.In this thesis,the effects of different TAMS parameters on the local potential signal in the hippocampus of SD rats and the effect of TAMS on the modulation of the brain were studied by means of the acouso-magnetic stimulation platform.The power spectra of local field potentials and firing rate of spikes were compared in different group,such as the control group,only the ultrasonic stimulation(TFUS)only group,the 0.04 T TAMS group and the 0.15 T TAMS group.The results showed that the power spectra of LFPs in acousto-magnetic coupling group was obviously higher than the control group and the ultrasonic stimulation group,the power spectra of LFPs increased with increasing the intensity of magnetic field in TAMS.The firing rate of spikes in TAMS group was obviously higher than the control group and the TFUS group,and the firing rate of spikes increased with increasing the intensity of magnetic field in TAMS.The results of this study can provide theoretical reference and basis for the development of transcranial magnetic and magnetic stimulation methods and systems,but also can provide useful information for the treatment and rehabilitation of neuropsychiatric diseases. |
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