Ultrasound Neuromodulation

A review examines the principles of functional ultrasound brain-computer interfaces and their research uses and potential clinical value in stroke assessment, epilepsy monitoring, and early identification of neurodegenerative diseases. Functional ultrasound detects cerebral blood volume changes through the relationship between neural activity and blood flow, with a spatial resolution of approximately 100 μm. Although imaging frames are acquired at intervals of 200–500 ms, the hemodynamic response limits effective temporal resolution to 1–2 s. The author notes that bidirectional closed-loop systems combining acquisition and neuromodulation remain at the proof-of-concept stage. The biosafety of chronic ultrasound exposure is still unclear, and decoding reliability under pathological conditions needs improvement.

Arbor Neuroscience plans to develop brain maps that track signal changes after neuromodulation and connect specific symptoms with neural circuits. Its goal is to guide treatment targeting by symptoms rather than diagnostic categories alone. Its predecessor, Forest Neurotech, developed Forest 17, a wearable functional ultrasound imaging device that observes brain activity through localized blood flow changes. A future version is intended to add focused ultrasound neuromodulation. These are research instruments for people who already have ultrasound-transparent skull-replacement implants, not devices that anyone can simply put on and use. Symptom-to-circuit mapping and treatment planning based on it remain organizational goals.

The study presents an integrated ultrasonic platform that delivers high-resolution, multi-point ultrasound energy through highly aberrating barriers such as the skull and ribs, with about ±6.5% intensity uniformity across foci, using a physics-constrained metasurface design framework, and demonstrates two adaptive stimulation paradigms — attention-gated and cardiac-synchronized stimulation. A dual-channel acoustic link sustains continuous transcranial wireless power and data streaming through a single ultrasonic metasurface, remaining robust even under a 400-fold power difference. The authors frame the platform as groundwork for next-generation ultrasound-based brain-computer interfaces (uBMI) and closed-loop bioelectronic therapies.