Brain-Computer Interfaces Based on Transcranial Doppler Ultrasound

Brain-Computer Interfaces Based on Transcranial Doppler Ultrasound

09/13/2011, 3:44 pm

Recent developments may yield practical brain computer interfaces (BCI) that work by using transcranial doppler ultrasound or related technologies.  TDU is an imaging technique that can record the movement of cerebral blood flow.  These types of scanning tools may possibly have benefits when compared to other technologies like an EEG.  Ultrasound is perhaps best known for its ability to image a fetus in the womb but it has numerous legitimate alternate applications as well.  Scientists at the Bloorview Research Institute in collaboration with other organizations have used sonography to investigate the practicality of a novel brain machine interface.

The scientists used high frequency sound pulses to classify the cerebral blood flow velocity changes in response to specific mental tasks.  Changes in the frequency of the waves are determined by the speed of the blood.  Blood perfusion is linked to the firing of brain cells.  They asked participants to perform either a visuo-spatial rotation, a word generation task or relax and do nothing.  The scientists were able to distinguish between the different assignments at a level greater than chance.  A few of the benefits of transcranial doppler sonography is that it is highly portable and light weight.   It is also less expensive when compared to functional magnetic resonance imaging or magneto-encephalography.  The temporal resolution is decent and this aspect allows it to decipher dynamic changes within the brain.  There are a lot of drawbacks that have prevented it from being employed in a few of these other industries.  Perhaps with new breakthroughs, though, a BCI based on very focused ultrasound could allow disabled people to move just by thinking.  This work only studies major blood vessels, but new developments mean tinier regions can be visualized as well.  It might be able to analyze the neural changes associated with motion and then translate those signals to operate a wheelchair or robotic appendage.  Functional micro-ultrasound can help scientists understand the inner workings of animal minds as a related example.  This recent study seems extremely crude and they only looked for activity in the major cerebral arteries.

Nano ultrasonic transducers are being synthesized by a number of organizations.  Nanotechnology can enhance the usability of the devices and may lead to very small parts that can be implanted on the head.  This could become a relatively non-invasive computer interface as the skull wouldn’t need to be breached.  The transducers could be put underneath the skin so they could deliver controlled pulses.  The military is also investigating portable ultrasonic imaging for use in battlefield areas.  The army may take advantage of better machine interfaces.  It remains to be seen if this could be used for complex BCIs.  There has been progress towards utilizing an EEG to attempt to read a person’s speech thoughts.  Certain regions of the brain related to speech are activated when a person is thinking to themselves.  This activity can potentially be read by a BCI and then translated into computer software that would read aloud those thoughts using an artificial voice synthesizer.  This can currently be done in a rudimentary way by using an fMRI.  The ultrasound or other portable modalities may never have the resolving power to be able to do this.  However, it is worth pursuing to create better next generation machine interfaces.

The paper is titled “A Brain-Computer Interface Based on Bilateral Transcranial Doppler Ultrasound

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