Functional ultrasound imaging in preclinical brain stimulation: from multimodal readouts to closed-loop neuromodulation.

Understanding how brain stimulation engages neural circuits requires readouts that combine rapid monitoring, access to deep structures, and high spatiotemporal resolution. Few existing modalities can provide this combination. This minireview summarizes recent advances in the application of functional ultrasound (fUS) imaging to preclinical brain stimulation, with an emphasis on its value as an advanced functional imaging modality across different stimulation paradigms. Building on ultrafast ultrasound, fUS captures cerebral hemodynamic changes associated with neural activity, enabling near-real-time hemodynamic monitoring with high spatiotemporal resolution. We survey the applications of fUS across optogenetic stimulation, deep brain stimulation (DBS), and focused ultrasound (FUS) stimulation, covering its role in mapping stimulation-evoked network responses and characterizing parameter-dependent neuromodulation effects. We further argue that the unique compatibility between fUS as a readout and FUS as an effector points toward a fully integrated read-write closed-loop neuromodulation framework, in which fUS continuously monitors brain hemodynamic states and feeds these signals back into an adaptive controller to deliver FUS. Together, these directions position fUS as an effective and promising tool for examining the mechanisms of brain function and its responses to stimuli and for developing precise, adaptive neuromodulation strategies.