Transcranial ultrasound neuromodulation of the contralateral visual field in awake monkey

In this work, we investigated the effect of low intensity pulsed focused ultrasound in the brain of two awake Maccaca Mulatta monkeys using the antisaccade (AS) paradigm. The objective of the study was to determine if transcranial ultrasound has an effect on behavioural tasks in awake animal involving a specific brain structure. Two Maccaca Mulatta monkeys (Y and L) were trained to perform antisaccade (AS) movements where they initially have to fix a central stimulus on a screen and then refrain from looking at an appearing peripheral target but instead initiate as soon as possible a saccade towards the opposite direction. In order to investigate the effect of low intensity focused ultrasound, a continuous 100 ms sonication pulse (derated pressure estimated at 0.35 ± 0.05 MPa) was focused at the frontal eye field using a 320 kHz transducer (H115, Sonic Concept, Bothell, WA, USA). Ipsilateral mean AS latencies with ultrasound stimulation were significantly (t-test;monkey Y: p=.0345, monkey L: p= .0311) increased compared to the non-stimulation condition (monkey Y: +14ms; monkey L: +15 ms). The study demonstrates the feasibility of using focused ultrasound to causally modulate behaviour in awake non-human primate brain.