SonoMagnetic Stimulation (SMS)

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Neurostimulation has become a cornerstone in both understanding neural circuitry and treating neurological and psychiatric disorders. Modern brain stimulation therapies have transformed care for conditions such as Parkinson’s disease, depression, dystonia, and epilepsy, and are being explored for Alzheimer’s disease, anxiety, schizophrenia, and stroke. Techniques including transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) manipulate neural activity using externally applied electrical currents. However, these methods are fundamentally limited by physics: electromagnetic fields cannot be tightly focused through biological tissue at depth. As a result, their reach is confined to superficial cortical regions or large, diffuse volumes, leaving deep brain structures largely inaccessible.

To overcome these constraints, ultrasonic neurostimulation has emerged as a promising noninvasive alternative capable of penetrating deep into the brain. Yet, its effects in humans have so far been substantially weaker than those achieved by TMS. This motivates the development of sonomagnetic stimulation (SMS)—a novel modality that combines ultrasonic and magnetic fields to induce localized electrical currents deep within neural tissue. By leveraging the interaction between acoustic and magnetic domains, SMS aims to achieve precise, focal activation of neurons at depths unreachable by existing methods. If successful, it would introduce a fundamentally new tool for probing brain function and treating neurological disease.

A broader strategy to bypass the long-standing trade-off between penetration and spatial precision is to induce energy transduction directly within the target region. Rather than transmitting highly focused waves from outside, localized secondary signals can be generated inside the medium itself. Analogies include photoacoustic imaging—where nanoscale absorbers convert light into ultrasound to achieve sub-millimeter resolution—and optogenetics, which enables cell-specific activation with light. However, both remain invasive. Our proposed magnetoacoustic approach, in contrast, relies on the Lorentz-force interaction between electric currents and magnetic fields in a conductive medium, generating acoustic waves or electric fields noninvasively. By combining radio-frequency and ultrasonic excitation, this hybrid mechanism achieves sharply localized effects at significant depth, breaking the conventional trade-off between resolution and penetration. This paradigm may open new frontiers in noninvasive neurostimulation, imaging, and sensing.

Publications

[1] M. S. Aliroteh, G. C. Scott, and A. Arbabian, "Frequency-Modulated Magneto-Acoustic Detection and Imaging: Challenges, Experimental Procedures, and B-Scan Images," arXiv preprint arXiv:1602.06931, 2016.

[2] A. S. Rekhi and A. Arbabian, "Remote sub-wavelength focusing of ultrasonically activated Lorentz current," Applied Physics Letters, vol. 110, no. 16, 2017.