Ultrasonic Brain Computer Interfaces for Enhancing Human-Machine Cognition

Low-intensity transcranial focused ultrasound (tFUS) is rapidly emerging as a transformative non-invasive brain stimulation (NIBS) modality characterized by high spatial resolution and ability to target deep brain circuits. Unlike electromagnetic techniques such as transcranial magnetic stimulation and transcranial direct current stimulation, which are constrained by centimeter-scale resolution and a depth-focality tradeoff, tFUS leverages mechanical pressure waves to modulate both superficial cortical and deep subcortical structures with millimeter precision. This article discusses recent scientific observations and engineering breakthroughs in the advancement of tFUS for next-generation ultrasonic brain-computer interfaces (uBCIs) and human-machine interfaces. These advancements move beyond open-loop systems and demonstrate closed-loop architectures that incorporate real-time electrophysiological feedback to optimize cognitive variables such as attention, learning, trust, and cooperation in various applications. Other advances in the development of ultrasound sensors for sonomyography to decode muscle activation and functional ultrasound to monitor hemodynamic brain activity are discussed as potential elements in bidirectional uBCIs. Together, these advances position ultrasound as a foundational technology for the development of intelligent, adaptive, and bidirectional neural interfaces that will seamlessly integrate human cognition with next-generation automation and robotic systems.