From the paper - they don't use ultrasound itself to generate the effect, they u...

george_pavlov on March 12, 2015 | parent | context | favorite | on: Ultrasound Restores Memory to Mice with Alzheimer’...

From the paper - they don't use ultrasound itself to generate the effect, they use ultrasound to activate injected 'micro-bubbles' in the brain which disrupt the blood-brain barrier.