January 13, 2014
Sensory Performance Could Be Enhanced Through Targeted Ultrasounds
redOrbit Staff & Wire Reports - Your Universe Online
Ultrasound, which is used by creatures such as bats and whales as a type of sensory guidance system, can also boost sensory perception in humans by modulating brain activity, according to new research appearing in Sunday’s online edition of Nature Neuroscience.
“Ultrasound has great potential for bringing unprecedented resolution to the growing trend of mapping the human brain's connectivity,” lead investigator and assistant professor Dr. William “Jamie” Tyler said in a statement. “So we decided to look at the effects of ultrasound on the region of the brain responsible for processing tactile sensory inputs.”
Dr. Tyler and his colleagues placed a small electrode on the wrist of human volunteers in order to stimulate their median nerve, which runs down the arm and is the only nerve to pass through the carpal tunnel.
They then recorded the study participants’ brain responses using electroencephalography (EEG), then just prior to stimulating the nerve, the researchers began delivering ultrasound the targeted region of the brain. The ultrasound both decreased the EEG signal and weakened the brain waves that encode tactile stimulation.
Afterwards, the researchers administered a pair of neurological tests: one that measures a person’s ability to distinguish that two objects touching the skin are actually distinct from one another, and one that measures sensitivity to the frequency of a series of air puffs.
“What the scientists found was unexpected,” the institute said in a statement. “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.”
Dr. Tyler said that the discovery was a surprise, because people improved at detecting differences in sensations even though the brain waves associated with that task had become weaker.
So why did suppressing the mind’s response to sensory stimulation actually heighten perception? The researchers speculated that the ultrasound must have had an impact on an essential neurological balance.
“It seems paradoxical, but we suspect that the particular ultrasound waveform we used in the study alters the balance of synaptic inhibition and excitation between neighboring neurons within the cerebral cortex,” Dr. Tyler explained.
“We believe focused ultrasound changed the balance of ongoing excitation and inhibition processing sensory stimuli in the brain region targeted and that this shift prevented the spatial spread of excitation in response to stimuli resulting in a functional improvement in perception,” he added.
In order to examine whether or not the effect could be accurately controlled, he and his colleagues moved the ultrasound one centimeter in either direction of the brain stimulation site.
The effect disappeared, leading Dr. Tyler to conclude that they could use the beam “to target an area of the brain as small as the size of an M&M.” He added that the discovery represents “a new way of noninvasively modulating human brain activity with a better spatial resolution than anything currently available.”