A Noninvasive Deep Brain Stimulation Method via Temporal-Spatial Interference Magneto-Acoustic Effect: Simulation and Experimental Validation

Deep brain transcranial stimulation is used in both research and for the treatment of neuropsychological diseases. Ideally, such stimulation should be noninvasive and precisely controlled. We propose a temporal-spatial interference magneto-acoustic stimulation (TIMAS) method combining transcranial magneto-acoustic stimulation (TMAS) and temporal interference stimulation (TIS) to achieve such stimulations, using the characteristics of the response of brain neurons to modulated low-frequency oscillation. Ultrasonic waves with two frequencies can interfere with each other to produce a modulated low-frequency signal. The modulated signal with difference frequency characteristics can be used for deep brain electrostimulation by means of magneto-acoustic coupling effect. A focused difference frequency electric field with a millimeter focal spot, a lateral resolution of 1.2 mm, an axial resolution of 6.4 mm, and a frequency of 4.13 kHz was achieved in the experimental system. These parameters are much better than previously reported magneto-acoustic coupling stimulation parameters. The measured electric field intensity for nerve stimulation was 137.2 mV/m, which meets the stimulation standard and reaches the threshold for effective nerve stimulation. Simulation and experimental results showed that TIMAS has superior penetration and temporal-spatial resolution and can generate a low-frequency envelope modulated electric field with a definite direction. TIMAS can be used as a new noninvasive low-frequency envelope modulated electrical stimulation, which can obtain high spatial resolution and high focus even at deep stimulation depths, and has low envelope frequency compared with the traditional TMAS. The method proposed in this article provides a new direction for the development of TMAS and is expected to be applied in brain science research and the treatment of major neuropsychiatric diseases related to deep brain regions.