10 June 2010

There's More than One Way Home

The ability to diagnose and treat brain dysfunction without surgery, may rely on a new method of noninvasive brain stimulation using pulsed ultrasound developed by a team of scientists led by William "Jamie" Tyler, a neuroscientist at Arizona State University. The approach, published in the journal Neuron on June 9, shows that pulsed ultrasound not only stimulates action potentials in intact motor cortex in mice but it also "elicits motor responses comparable to those only previously achieved with implanted electrodes and related techniques," says Yusuf Tufail, the lead author from ASU's School of Life Sciences. _Physorg

Scientists are developing better methods for using ultrasound to diagnose brain disorder, to treat serious brain pathologies such as tumours, and to stimulate more optimal brain function in diseases such as Alzheimer's and epilepsy. There are so many possible uses for ultrasound in the brain, that a person could get lost trying to get a mental grasp all of them.
"Scientists have known for more than 80 years that ultrasound can influence nerve activity," observes Tufail. "Pioneers in this field transmitted ultrasound into neural tissues prior to stimulation with traditional electrodes that required invasive procedures. Those studies demonstrated that ultrasound pre-treatments could make nerves more or less excitable in response to electrical stimulation.
"In our study, however, we used ultrasound alone to directly stimulate action potentials and drive intact brain activity without doing any kind of surgery," Tufail says. _Physorg
Ultrasound can also affect growth factors -- such as BDNF -- and patterns of nerve discharge. This opens the door to cognitive therapies using ultrasound.
In addition to advancing hope for noninvasive treatments of brain injury and disease, the groups' experiments in deeper subcortical brain circuits also revealed that ultrasound may be useful for modifying cognitive abilities.

"We were surprised to find that ultrasound activated brain waves in the hippocampus known as sharp-wave ripples," Tufail says. "These brain activity patterns are known to underlie certain behavioral states and the formation of memories."

The scientists also found that ultrasound stimulated the production of brain-derived neurotrophic factor (BDNF) in the hippocampus -- one of the most potent regulators of brain plasticity.

Tyler says the fact that ultrasound can be used to stimulate action potentials, meaningful brain wave activity patterns, and BDNF leads him to believe that, in the future, ultrasound will be useful for enhancing cognitive performance; perhaps even in the treatment of cognitive disabilities such as mental retardation or Alzheimer's disease. _SD

PLoS study (2008) by William Tyler et al looks at some basic science of the technology.

Technology Review article on brain ultrasound therapeutics

An IEEE Spectrum look at using ultrasound for brain stimulation

Short review article describing ultrasonic deep brain stimulation

Synsonix, tech startup which includes William Tyler among its founders.

More information from Brain Stimulant

Ultrasound is only one of many technologies for intervening safely in brain dysfunction and pathology. Other methods include transcranial electromagnetic stimulation and the implantation of electrodes and transducers deep within the brain itself -- intracranial stimulation. Ultrasound has the advantage of being fairly well studied in most body tissues, so that the limits of diagnostic and therapeutic uses of ultrasound are fairly well known in general.

Getting approval from the ethics committee to study ultrasonic brain stimulation is much easier than getting permission to implant electrodes and transducers into deep brain tissue -- or even just under the dura.

That is one of many reasons why the study of ultrasonic brain stimulation should advance fairly quickly. Stay tuned.

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