Ultrasound shown to exert remote control of brain circuits

In a twist on nontraditional uses of ultrasound, a group of
neuroscientists at Arizona State University has developed pulsed
ultrasound techniques that can remotely stimulate brain circuit
activity. Their findings, published in the Oct. 29 issue of the
journal Public Library of Science (PLoS) One, provide insights into
how low-power ultrasound can be harnessed for the noninvasive
neurostimulation of brain circuits and offers the potential for new
treatments of brain disorders and disease.

While it might be hard to imagine the day where doctors could treat
post traumatic stress disorders, traumatic brain injury and even
Alzheimer's disease with the flip of a switch, most of us have in
fact experienced some of ultrasound's numerous applications in our
daily lives. For example, ultrasound has been used in fetal and other
diagnostic medical imaging, ultrasonic teeth cleaning,
physiotherapies, or surgical ablation. Ultrasound also provides a
multitude of other non-medical uses, including pharmaceutical
manufacturing, food processing, nondestructive materials testing,
sonar, communications, oceanography and acoustic mapping.

"Studies of ultrasound and its interactions with biological tissues
have a rich history dating back to the late 1920s," lead investigator
William "Jamie" Tyler points out. "Several research groups have, for
more than a half-century, demonstrated that ultrasound can produce
changes in excitable tissues, such as nerve and/or muscle, but
detailed studies in neurons at the cellular level have been lacking."

"We were able to unravel how ultrasound can stimulate the electrical
activity of neurons by optically monitoring the activity of neuronal
circuits, while we simultaneously propagated low-intensity, low-
frequency ultrasound through brain tissues," says Tyler, assistant
professor of neurobiology and bioimaging in the School of Life
Sciences in the College of Liberal Arts and Sciences.

Led by Tyler, the ASU research group discovered that remotely
delivered low intensity, low frequency ultrasound (LILFU) increased
the activity of voltage-gated sodium and calcium channels in a manner
sufficient to trigger action potentials and the release of
neurotransmitter from synapses. Since these processes are fundamental
to the transfer of information among neurons, the authors pose that
this type of ultrasound provides a powerful new tool for modulating
the activity of neural circuits.

"Many of the stimulation methods used by neuroscientists require the
use and implantation of stimulating electrodes, requiring direct
contact with nervous tissue or the introduction of exogenous
proteins, such as those used for the light-activation of neurons,"
Tyler explains.

The search for new types of noninvasive neurostimulation methods led
them to revisit ultrasound.

"We were quite surprised to find that ultrasound at power levels
lower than those typically used in routine diagnostic medical imaging
procedures could produce an increase in the activity of neurons while
higher power levels produced very little effect on their activity,"
Tyler says.

Other neuroscientists and engineers have also been rapidly developing
new neurostimulation methods for controlling nervous system activity
and several approaches show promise for the treatment of a wide
variety of nervous system disorders. For example, Deep Brain
Stimulation (DBS) and Vagal Nerve Stimulation (VNS) have been shown
to be effective in the management of psychiatric disorders such as
depression, bipolar disorders, post-traumatic stress disorder, and
drug addition, as well as for therapies of neurological diseases such
as Parkinson's disease, Alzheimer's disease, Tourette Syndrome,
epilepsy, dystonia, stuttering, tinnitus, recovery of cognitive and
motor function following stroke, and chronic pain. Up until now,
these two techniques have captured the attention of physicians and
scientists; however, these therapies still pose risks to patients
because they require the surgical implantation of stimulating
electrodes. Thus, these types of therapies are often only available
to patients presenting the worst of prognoses.

One prior stumbling block to using ultrasound noninvasively in the
brain has been the skull. However, the acoustic frequencies utilized
by Tyler and his colleagues to construct their pulsed ultrasound
waveforms, overlap with a frequency range where optimal energy gains
are achieved between transcranial transmission and brain absorption
of ultrasound – which allows the ultrasound to penetrate bone and yet
prevent damage to the soft tissues. Their findings are supported by
other studies examining the potential of high-intensity focused
ultrasound for ablating brain tissues, where it was shown that low-
frequency ultrasound could be focused through human skulls.

When asked about the potential of using his groups' methods to
remotely control brain activity, Tyler says: "One might be able to
envision potential applications ranging from medical interventions to
use in video gaming or the creation of artificial memories along the
lines of Arnold Schwarzenegger's character in 'Total Recall.' Imagine
taking a vacation without actually going anywhere?

"Obviously, we need to conduct further research and development, but
one of the most exhilarating prospects is that low intensity, low
frequency ultrasound permit deep-brain stimulation procedures without
requiring exogenous proteins or surgically implanted medical
devices," he adds.

Tyler and the other ASU researchers will now focus on further
characterization of the influence of ultrasound on intact brain
circuits and translational research, taking low intensity ultrasound
from the lab into pre-clinical trials and treatment of neurological
diseases.

Source: Arizona State University
http://www.physorg.com/printnews.php?newsid=144495604