Sonications were applied transcranially under MRI guidance (see Supplementary Methods for parameters). In monkeys 1–3 (four sessions), burst sonications were delivered to individual points in the brain (35 targets overall). In the subsequent 26 sessions (monkeys 4–7), nine locations in a 3×3 grid in a single plane were targeted during each sonication (Supplementary Fig. S1B–C). During these volumetric sonications, 10 ms bursts were applied in sequence to the nine locations. The focal point was advanced to the next location every 100–400 ms, yielding an effective pulse repletion frequency at each location of 1.1–0.28 Hz. Spacing between the targets in these volumetric sonications was 2 mm, yielding a roughly cubic region of BBB disruption with dimensions of ~1 cm3.
Overall, 185 locations or volumes were sonicated in the seven monkeys. In monkeys 1–4, a range of acoustic power levels, microbubble injection/infusion parameters and brain targets were evaluated. Targets included the thalamus, putamen, cingulate cortex, visual cortex, hippocampus, and white matter structures. Sonications centered on the lateral geniculate nucleus (LGN) included the hippocampus and part of the optic tract. The third animal was tested twice over two weeks, and the fourth was tested 13 times over 26 weeks.
In the trials that targeted single locations per sonication and in 45 volumetric sonications, the microbubble USCA (Definity, Lantheus Medical Imaging) was injected as a bolus at the start of each sonication (dose: 10 µl/kg). These sonications consisted of 10 ms bursts applied at 1 Hz for 70s. Subsequent tests at 82 locations with volumetric sonication used an infusion pump (Spectra Solaris EP, Medrad) to deliver microbubbles throughout the exposures. Most (67/82) sonications with infusion used a 20 µl/kg microbubble dose and a 150 s total sonication duration; see Supplemental Methods for more details on the infusion protocol.