Dose-dependent ultrasound neuromodulation of the human brain

Transcranial ultrasound stimulation (TUS) can noninvasively modulate deep brain structures, but the relationship between delivered dose and neuromodulatory response remains poorly characterized in humans. Here, we show that ultrasound-induced tissue displacement measured in vivo predicts local and downstream functional neuromodulation. In 24 healthy adults, we combined magnetic resonance acoustic radiation force imaging (MR-ARFI) with concurrent TUS-fMRI in a double-blind, counterbalanced, within-subject design. Relative to active control stimulation, targeting the lateral geniculate nucleus (LGN) increased visually evoked BOLD responses in the LGN and ipsilateral primary visual cortex, localized to the retinotopic projection zone of the stimulated LGN site. Displacement predicted effect magnitude in both regions across participants and covaried with voxelwise responses within participants. Simulated in situ intensity showed no significant association with displacement or neuromodulatory response. These findings link in vivo mechanical displacement to functional modulation of a human thalamocortical circuit, providing an empirical basis for individualized dosing in causal neuroscience and clinical intervention.