Model And Experimental Study Of Neural Current Non-invasive Detection Based On Magneto-acoustic Technique

With the progress of Human Brain Project, neuroinformatics has been promptly developed in recent years. Noninvasive detection of neural current and precise stimulation of the nerve are under study. Magneto-acoustic methods are attractive because of their noninvasive characters.In the presence of an externally applied magnetic field, bioelectric action current, arising from active nerve, experiences a Lorentz force. The resulting pressure or tissue displacement contains information about the action current. A theoretical model of this magneto-acoustic current detection is set up, based on fundamental equations of continuum mechanics and electromagnetism. And the capabilities and limitations of this method are accessed. Then a testing system is designed to detect current of micro-ampere to milliampere level. The experimental results show that the acoustic response is proportional to the current in the tissue.Neural current is different from the normal current for its velocity. Neural cable mode is constructed to simulate the slow current. Experimental results show that the corresponding acoustic response is also linear with the current flowing in the model.A novel method to stimulate active tissue is proposed by transmitting ultrasound into the tissue in the presence of a magnetic field. Since the tissue is conductive, particle motion created by an ultrasonic wave induces an electric current density generated by the Lorentz forces. A model is presented to simulate the axon stimulated by the ultrasonic wave to cause an exciting current in the tissue. The proposed method can be used to stimulate active tissue in regions where the ultrasound is focused. The stimulated area can be limited within millimeter order.Magneto-acoustic technique can be used to detect neural current non-invasively as well as to stimulate the active tissue in a small area.