The study provides the first demonstration that low-intensity, transcranial-focused ultrasound can modulate human brain activity to enhance perception. (Agencies)
"Ultrasound has great potential for bringing unprecedented resolution to the growing trend of mapping the human brain's connectivity," said William 'Jamie' Tyler, assistant professor at Virginia Tech Carilion Research Institute.
"So we decided to look at the effects of ultrasound on the region of the brain responsible for processing tactile sensory inputs," he said.
The scientists delivered focused ultrasound to an area of the cerebral cortex that processes sensory information received from the hand, said the study published in Nature Neuroscience.
To stimulate the median nerve - a major nerve that runs down the arm and the only one that passes through the carpal tunnel - they placed a small electrode on the wrist of human volunteers and recorded their brain responses using electroencephalography or EEG.
Just before stimulating the nerve, they began delivering ultrasound to the targeted brain region.
The scientists found that the ultrasound decreased the EEG signal and weakened the brain waves responsible for encoding tactile stimulation.
The scientists then administered two classic neurological tests - the two-point discrimination test that measures a subject's ability to distinguish whether two nearby objects touching the skin are truly two distinct points, rather than one.
The second is the frequency discrimination task - a test that measures sensitivity to the frequency of a chain of air puffs. They found unexpected results.
The subjects receiving ultrasound showed significant improvements in their ability to distinguish pins at closer distances and to discriminate small frequency differences between successive air puffs.
“Even though the brain waves associated with the tactile stimulation had weakened, people actually got better at detecting differences in sensations," said Tyler, adding that the ultrasound affected an important neurological balance.
"We believe focused ultrasound changed the balance of ongoing excitation and inhibition processing sensory stimuli in the brain region, resulting in a functional improvement in perception,” he added.
The study said, “This approach can be used for potential treatments of neurodegenerative disorders, psychiatric diseases and behavioural disorders.”
The study provides the first demonstration that low-intensity, transcranial-focused ultrasound can modulate human brain activity to enhance perception.