# Rapid modulation of choice behavior by ultrasound on the human frontal eye fields

## TL;DR

Ultrasound can rapidly influence eye movement decisions in humans by targeting the frontal eye fields, with effects linked to brain chemistry.

## Contribution

Demonstrates temporally precise ultrasound effects on human brain circuits and links response magnitude to baseline neurophysiological state.

## Key findings

- Ultrasound to frontal eye fields biases eye movement in perceptual tasks.
- Response magnitude correlates with individual baseline GABAergic inhibitory tone.
- Effects are specific to frontal eye fields, not motor cortex.

## Abstract

A fundamental challenge in neuroscience is establishing causal brain-function relationships with spatial and temporal precision. Transcranial ultrasonic stimulation offers a unique opportunity to modulate deep brain structures non-invasively with high spatial resolution, but temporally precise effects and their neurophysiological foundations have yet to be demonstrated in humans. Here, we develop a temporally precise ultrasound stimulation protocol targeting the frontal eye fields — a well-characterized circuit critical for saccadic eye movements. We demonstrate that ultrasonic stimulation induces robust excitatory behavioral effects. Importantly, individual differences in baseline GABAergic inhibitory tone predict response magnitude. These findings establish ultrasound stimulation as a reliable tool for chronometric circuit interrogation and highlight the importance of neurophysiological state in neuromodulation. This work bridges human and animal research, advancing targeted transcranial ultrasonic stimulation applications in neuroscience and clinical settings.

Brief ultrasound to human frontal eye fields, but not motor cortex, rapidly biases eye movement contralaterally in a perceptual choice task. The size of this effect scales with individual baseline FEF inhibitory tone.