Monday, 13 January 2014

Effect of ultrasound to Human Brain: Boost Sensory Performance!

Up till now, it was well known that bats, whales and many other praying mantises make use of ultrasound to guide them and sense the movement and presence of their prey. However,  William "Jamie" Tyler, an assistant professor at the Virginia Tech Carilion Research Institute and his colleagues, have presented a new study that shows that ultrasound can even modulate brain activity and heighten sensory perception in humans. When directed to a specific region of a brain: Transcranial region in low intensity, ultrasound can enhance performance in sensory discrimination. This study has been published online in Nature Neuroscience. 
Scientists of Virginia Tech Carilion Research Institute analysed the effects of ultrasound on that region of brain which is responsible for dealing with tactile sensory inputs since Ultrasound has great potential for bringing resolution to the mapping of human brain's connectivity
A focused ultrasound was delivered to an area of the cerebral cortex that processes sensory information received from the hand. A median nerve is a major nerve that runs down the arm as it is the only one that passes through the carpal tunnel. A small electrode was placed on the wrist of human volunteers and their brain responses were recorded using electroencephalography, or EEG. Before stimulating median nerve, ultrasound was directed to target region of brain.
It was observed that EEG signal decreased and brain waves responsible for encoding tactile stimulation were also weakened due to ultrasound.
The scientists then administered two classic neurological tests:
1)   The two-point discrimination test, which analyses a subject's ability to distinguish whether two close by objects touching the skin are two distinct points, rather than one;
2)   The frequency discrimination task, a test that measures sensitivity to the frequency of a chain of air puffs.
Results were unexpected.
The subjects that  received ultrasound showed improvements in their ability to distinguish pins at nearer distances and also discriminated small frequency differences between successive air puffs.
Suppression of brain responses to sensory stimulation heightens perception. Thus, ultrasound affected an important neurological balance. Tyler explained that this is due to the fact that the particular ultrasound waveform used in the study alters the balance of synaptic inhibition and excitation between neighboring neurons within the cerebral cortex. Focused ultrasound changed the balance of ongoing excitation and inhibition processing sensory stimuli in the brain region targeted and this shift prevented the spatial spread of excitation in response to stimuli resulting in a functional improvement in perception. When the acoustic beam was moved one centimeter in either directions of the original site of brain stimulation, it was seen that effect disappeared.
This discovery represents a new way of noninvasively modulating human brain activity with a better spatial resolution than anything currently existing: Transcranial magnetic stimulation, which uses magnets to activate the brain, and Transcranial direct current stimulation, which uses weak electrical currents delivered directly to the brain through electrodes placed on the head.This will further enhance mapping of the richly interconnected synaptic circuits in human brain. Moreover, work is going on to extend the capabilities of ultrasound for non-invasively tweaking brain circuits to help us understand how human brain works.