Summary: Researchers have successfully altered human reward learning using non-invasive transcranial ultrasound stimulation targeting a deep brain structure linked to motivation. After brief stimulation, participants learned faster from more consistently repeated positive feedback and rewarding choices.
The effects mirrored key aspects of surgical deep brain stimulation, but without implants or incisions. The findings suggest that ultrasound could become a personalized and safer tool to remodel faulty reward circuits in mental health disorders.
Key facts
Deep brain targeting: Ultrasound successfully modulated the nucleus accumbens without surgery. Faster reward learning: Participants showed greater sensitivity to positive outcomes after stimulation. Therapeutic potential: The technique could one day help treat addiction, depression and eating disorders.
Source: University of Plymouth
The nucleus accumbens is a small element of the human brain that is activated when we experience something pleasant and is used to help us learn behaviors that lead to rewards.
A new study has shown for the first time that its influence on human behavior can be modified by transcranial ultrasound stimulation (TUS).
By applying the technique for just over a minute at a time, the researchers were able to influence how people learned the links between certain cues and rewards.
The result was that they were more likely to repeat a previously worthwhile choice, their learning rates after positive outcomes increased, and they were more likely to make positive decisions more quickly.
Until now, these results have only been achieved through surgical procedures such as deep brain stimulation (DBS), which involves directly connecting electrodes to areas within a person’s brain.
However, those involved in the current study say their findings could indicate that TUS has the potential to be used as an equally beneficial (and non-invasive) alternative to help those affected by neurological or psychiatric disorders, including addictions, depression and eating disorders.
The study is published in the journal Nature Communications and was led by researchers at the University of Plymouth. It also involved the University of Oxford, John Radcliffe Hospital, University Hospitals Plymouth NHS Trust, Brown University and the VA Providence Healthcare System.
Professor Elsa Fouragnan, director of the Therapeutic Ultrasound Center and Brain Imaging and Research Center (BRIC) at the University of Plymouth, led the research.
She said: “For decades, the nucleus accumbens has been at the center of theories of motivation and reinforcement learning. It is the center where dopamine signals and limbic inputs converge to shape how strongly rewards influence our choices.
“We were able to identify a clear link between a specific learning trait, linked to impulsivity, and a structure that until now could not be reached without surgery. The fact that we can now modulate this area in a non-invasive and personalized way opens extraordinary possibilities for clinical translation.”
The study is part of ongoing, pioneering research being carried out at the University of Plymouth into the benefits of SUD for conditions including anxiety and depression, addiction and other neurological or psychiatric disorders.
In this project, the researchers recruited 26 healthy participants who visited the BRIC facility four times: once to plan their TUS intervention, followed by three sessions in which TUS was applied to different parts of their brain.
Approximately 10 minutes after the ultrasound intervention, participants were placed in the scanner to perform a series of tasks for an hour while the research team monitored changes in their behavior and brain activity.
The participants’ performance on the tasks was also compared to that of patients with bilateral deep brain stimulation electrodes targeting the nucleus accumbens as part of therapies for treatment-resistant anorexia nervosa.
The results showed that while deep brain stimulation often normalizes reward-seeking behavior, TUS had an opposite and excitatory effect; However, both outcomes alter people’s learning and sensitivity to rewards.
Professor Fouragnan added: “This study is the most important I have had the privilege of leading so far. We discovered a clear link between a specific cognitive process and a deep brain structure that, until now, was out of reach without surgery. It marks a turning point for neurotechnology, demonstrating that a non-invasive ultrasound approach can influence behavior and may one day help restore mental balance.”
Key questions answered:
A: A deep reward center called the nucleus accumbens that guides motivation and learning.
A: People learned faster from positive outcomes and more frequently repeated rewarding choices.
A: Similar effects previously required invasive brain surgery.
Editorial notes:
This article was edited by a Neuroscience News editor. Magazine article reviewed in its entirety. Additional context added by our staff.
About this neurotechnology and learning research news
Author: Alan Williams
Source: University of Plymouth
Contact: Alan Williams – University of Plymouth
Image: Image is credited to Neuroscience News.
Original research: Open access.
“Noninvasive ultrasonic neuromodulation of the human nucleus accumbens affects reward sensitivity” by Elsa Fouragnan et al. Nature Communications
Abstract
Noninvasive Ultrasonic Neuromodulation of the Human Nucleus Accumbens Affects Reward Sensitivity
Specifically, neuromodulation of deep regions of the brain could provide transformative advances in both neuroscience and treatment.
We demonstrate that noninvasive transcranial ultrasound stimulation (TUS) can selectively modulate deep brain activity and affect learning and decision making, comparable to deep brain stimulation (DBS).
We tested whether TUS could causally influence neural and behavioral responses by targeting the nucleus accumbens (NAcc) using a reinforcement learning task.
Twenty-six healthy adults completed a within-subject TUS-fMRI experiment with three conditions: TUS to the NAcc, dorsal anterior cingulate cortex (dACC), or Sham. After TUS, participants performed a probabilistic learning task during fMRI.
TUS-NAcc modified BOLD responses to reward expectations in and around the NAcc.
It also affected reward-related behaviors, including the use of win-stay strategies, the rate of learning after rewards, learning curves, and repetition rates of rewarded choices. DBS-NAcc disrupted the same characteristics, confirming target compromise.
These findings establish that TUS is a viable approach for non-invasive deep brain neuromodulation.
