Even when you aren’t doing anything, your brain is relentlessly active—daydreaming, ruminating, contemplating the past or future. How this mind wandering functions can significantly shape a person’s internal conscious experience.
In a study of 30 participants, researchers applied low-intensity ultrasound waves to a brain region associated with introspection and off-task mind wandering. Participants who underwent five minutes of ultrasound stimulation reported significantly heightened mindfulness—the ability to be fully present in the moment, without judgment toward others or the self. The results were published in June 2024 in Frontiers in Human Neuroscience.
“I haven’t seen ultrasound technology used in this way, but this type of neuromodulation has significant potential to change how we think about and enhance mindfulness,” says University of Wisconsin–Madison social psychologist Hadley Rahrig, who also has studied that state of mind.
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The researchers targeted the brain’s default mode network (DMN), a constellation of interconnected areas that become particularly active when the mind disengages with the outside world and drifts into activities such as reminiscing or envisioning the future. Abnormal DMN activity and connectivity have been linked to anxious rumination and depressive symptoms. “You get stuck, where your mind just keeps going and you can’t stop it. We hypothesized that we could use ultrasound stimulation to remove some stickiness and let the network cool off,” says the 2024 study’s lead author, Brian Lord, a cognitive neuroscientist at the University of Arizona.
Since the DMN was described in 2001, scientists have sought to manipulate it through broad-brush methods such as meditation and psychedelic drug therapy. But it remained difficult to precisely adjust DMN function because of its deep-brain location.
To overcome this challenge, Lord and his team used transcranial-focused ultrasound, a technique that converts electric current into concentrated and localized acoustic waves. (Half the participants received sham ultrasound as a control.) These waves can penetrate brain regions with millimeter-level precision and with greater depth than other noninvasive stimulation methods, which typically use magnetic fields or scalp-attached electrodes to induce electric currents spread over several centimeters.
Functional magnetic resonance imaging showed that the researchers successfully inhibited activity in the posterior cingulate cortex, a key area in the DMN linked to emotional regulation and concentration during meditation. Through questionnaires and an interview, participants in the treatment group reported at least 30 minutes of subjective effects akin to entering a deep meditative state: a distorted sense of time, fewer negative thoughts and an improved ability to detach from their feelings. Other scientists at the University of Arizona have investigated this technique as a possible treatment for mood disorders such as depression.
“One of the greatest barriers to meditation and mindfulness is the steep learning curve. Brain stimulation can act like training wheels for the mind, helping people achieve that deep state of consciousness,” Lord says. “That’s our larger goal.”