Scientists Controlled the Behavior of Monkeys by Zapping Their Brains With Ultrasound Waves

Scientists have managed to control the behaviour of monkeys by zapping their brains with ultrasonic waves.

Researchers from the University of Utah and Stanford University harnessed a non-invasive device similar to an ultrasound wand used for medical scans to direct inaudible, high frequency sound waves at the brains of two monkeys in a lab.

The macaques were each placed in front of a screen. The animals were initially shown a target in the center of a screen, before other targets on the left and right-hand side popped up one after the other in quick succession. The researchers noted the monkeys were most likely to look at the first target to appear.

But the scientists were able to change the animals' behavior when they directed low-intensity ultrasonic waves to an area of the frontal cortex, which controls eye movement. The waves remotely activated certain neurons which affect these movements, and enabled the researchers to make the monkeys look either left or right.

As the team hoped would happen, targeting an area called the left frontal eye field made the monkeys look right the majority of the time, and when they targeted the right frontal eye field they looked left in most cases.

When the researchers zapped the motor cortex, which does not play a role in perceptual decision-making, nothing happened.

Each ultrasound blast was applied for 300 milliseconds in total, and started 100 milliseconds before the first target appeared to ensure the team were tweaking the neurons before the monkeys started their decision-making.

"The effects of ultrasonic neuromodulation on behavior are likely to be maximized when a subject is making a decision," the team wrote in a paper published in the journal Science Advances.

The ultrasound was delivered in blocks of three to six trials, separated by three to six trials without ultrasound. Over time, the effect became weaker, and no longer significant by the fifth time the stimulus was applied, indicating the monkeys adapted to the waves over time.

The researchers argued there are "tantalizing opportunities" to apply this approach to change behaviour in humans, firstly to find the circuits involved in different disorders. If, for instance, doctors could pinpoint the brain circuits that drive a person's craving for an addictive drug, targeting them could potentially help them to stop using, the team hypothesized.

monkey, stock, macaque, getty
A stock image shows a macaque monkey, similar to the animals used in the study. Getty

"This result takes us a step closer to being able to modulate, non-invasively and reversibly, neuronal activity in specific brain circuits," they wrote. "This could open the way to future systematic studies of brain function in humans and to targeted personalized treatments of brain disorders," they wrote. "The ability to influence choice behavior non-invasively without using drugs could provide new ways to diagnose and treat disorders of choice."

Lead author Jan Kubanek, assistant professor in biomedical engineering at the University of Utah, said their approach is not invasive unlike some other existing neuromodulation techniques. It also is better at targeting certain parts of the brain.

"Brain disorders should be treated in a targeted and personalized ways instead of offering patients cocktails of drugs," he said. "But to do that, we need a tool that provides noninvasive, precise, and personalized treatments, to address the source of the problem in each individual.

"This up until now has only been a dream."