Ultrasound

Ultrasound - echoing acoustic frequencies that are undetectable to the human ear - is already a common guidance tool for some animals, including bats and whales. As far back as 1929, experiments had shown that ultrasound affected the nerves, muscles and eyes of frogs and turtles.

Subsequent studies involving cats, mice, rats, rabbits and monkeys also revealed that controlled exposure to ultrasound could disrupt seizures or cause other controlled changes to brain function.

But this new study, conducted by scientists at the Virigina Tech Carilion Research Institute and published in the journal Nature Neuroscience, is the first to show evidence that focused, low-intensity ultrasound can have a positive, measurable effect on human brain function.

Researchers focused an acoustic beam of ultrasound at the area of the cerebral cortex responsible for processing sensory information from the hand in human volunteers. The scientists then stimulated the major nerve running through the arm by placing an electrode on the volunteers' wrists.

The responses in the volunteers' brains were measured using electroencephalography (EEG), and two traditional neurological tests were used to record how accurately the subjects could distinguish between the sensations of pins or puffs of air touching the skin.