A new study has found that using ultrasound to target specific areas of the brain causes functional changes that last for up to an hour. The findings pave the way for the development of non-invasive methods of treating mental health conditions such as depression and anxiety.
Typically, ultrasound is used to examine internal body structures by sending out diffuse sound waves and recording the reflected sound or echoes to create an image. However, low-intensity transcranial ultrasound stimulation (TUS) can target both surface and deep brain regions with very high specificity, placing ultrasonic pressure on a region of the brain that changes the way neurons interact.
Researchers from the University of Plymouth in the UK led a study to test the effects of TUS on brain function, finding that it produced significant changes.
They recruited 24 healthy adults to investigate how TUS affected levels of gamma-aminobutyric acid (GABA) and connectivity between brain regions. GABA is the primary inhibitory neurotransmitter in the brain, it reduces a neuron’s ability to send and receive chemical messages. Specifically, GABA affects how the body reacts to feelings of anxiety, fear, and stress.
All participants completed three theta-burst TUS sessions, with an MRI after each session to assess changes to brain function. Theta-burst TUS is a form of brain stimulation that delivers short bursts at high frequencies, closely mimicking the natural rhythms of activity in the neurons. It’s thought to promote plasticity, the ability of the brain to form and reorganize neural connections in response to learning or experience.
The researchers found that TUS applied to the posterior cingulate cortex (PCC), an area deep in the brain associated with emotion and memory, reduced GABA levels in that region for up to an hour after treatment. They also found that the way the PCC communicated with the rest of the brain (functional connectivity) improved over that time. The PCC has been found to be abnormal across a range of psychiatric disorders.
When TUS was applied to the dorsal anterior cingulate cortex (dACC) – the region implicated in emotion, empathy, impulse control and decision-making, and, like the PCC, in psychopathology – the researchers did not see the same decrease in GABA levels, but they did see an increase in functional connectivity.
The researchers say their findings demonstrate that TUS is effective in humans, producing reversible changes in the brain. Although further study is required, they say it’s the first step to developing a non-invasive means of treating mental health conditions.
“If you are taking medication for depression, for example, the drug will impact the entire brain, and clinicians have very limited control over where the drug goes and what it does,” said Elsa Fouragnan, corresponding author of the study. “We already know that specific regions of the brain (and some of their connections) are dysfunctional in certain conditions, but other regions can work perfectly well. This study provides us with the genuine potential to think about using ultrasound for more targeted interventions in people with a range of mental health conditions.”
The researchers are already exploring whether TUS can be used to alter the brain’s dopaminergic system, the main reward pathway that detects and interprets rewarding stimuli such as food, sex, and drugs of abuse.
The study was published in the journal Nature Communications.
Source: University of Plymouth