To Read Monkey Brains and Predict Their Movement, Scientists Used Ultrasound

Researchers have recently used ultrasound imaging to predict the intended eye or hand movements of a monkey -- information that could create commands for a computer cursor or a robotic arm.

Science reported that the most advanced mind-controlled devices being tested in humans depend on small wires inserted into the brain.

If this approach can be improved, it may provide people who are paralyzed a new way to control prostheses minus the equipment that's penetrating the brain.

According to neuroscientist Krishna Shenoy from Stanford University, this research will put ultrasound on the map as a "brain-machine interface technique." Shenoy, who was not part of this new work also said, adding this machine to the toolkit is spectacular.

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Functional Ultrasound and fMRI

For a long time now, doctors have been using sound waves with frequencies outside the range of human hearing to produce images of the innards.

A device also known as a transducer is sending ultrasonic pings into the body, bouncing back to specify the boundaries between different fluids and tissues.

About 10 years ago, scientists discovered an approach to adapt ultrasound for brain imaging. This method, also called functional ultrasound. It uses broad, flat plane of sound rather than a thin beam to capture a huge area faster than with a traditional ultrasound machine.

Similar to functional magnetic resonance imaging or fMRI, functional ultrasound measures changes in blood flow, indicating when neurons are active and disbursing energy.

However, it produces images with finer resolution compared to fMRI and does not need participants to lie in a huge scanner.

According to California Institute of Technology or Caltech's neuroscientist Richard Anderson, the technique still necessitates taking out of a small piece of skull, although unlike implanted electrodes that directly reads the electrical activity of neurons, it does not engage opening the protective membrane of the brain.

Neural Activity Revealed

Anderson, who is a co-author of this new research explained, functional ultrasound can read from regions deep in the brain minus penetrating the tissue.

Still, Caltech biochemical engineer Mikhail Shapiro and co-author of Andersen said, measuring neural activity from a distance means sacrificing certain speed and precision.

The co-author added, compared with the readings of electrodes, functional ultrasound provides a signal that's less direct and thus, there was a question on the amount of information or ultrasound images really contain.

Furthermore, as indicated in their study published in Neuron (Single-trial decoding of movement intentions using functional ultrasound neuroimaging), the images could reveal neural activity as the brain got ready for a movement. However, the question now is, if there was sufficient detail in that indicator for a computer to decode the intended move.

To find an answer to the question, the study authors slotted small ultrasound transducers approximately the shape and size of a domino into two rhesus macaque monkeys' skulls.

Use of Functional Ultrasound Data on the Monkey Brain

A pair of previous research has used functional ultrasound data on the monkey brain for the reconstruction of what the animals were seeing or the movements of their eyes.

Nevertheless, doing that required averaging signals through long periods or multiple movements. In this new research, the study investigators collected sufficient data to make prediction in every run of the experiment, every time the monkey was planning to move.

Monash University neuroscientist Maureen Hagan who has examined how the brain is orchestrating movements said, that's an important feature.

A robotic arm's user would want to think about their intended movement just once for the arm to move, for instance. Hagan added that one wouldn't want subjects to have to do a lot of attempted or intended movements to decode their intentions.

A key next step, Shenoy explained, will be the use of computer predictions in real-time to guide a cursor or robot hand.

Related information about fMRI is shown on NIBIB gov's YouTube video below: