Researchers at the University of Texas at Austin have developed a soft, wearable patch that can specifically influence REM sleep. The device, called NEUSLeeP, combines gentle, focused ultrasound stimulation with electrodes that simultaneously record the brain’s electrical activity. What makes it unique is that the patch is worn directly on the skin and is designed to reach deeper regions of the brain during natural sleep. At the same time, it can monitor brain activity.

In an initial study involving 28 participants, the participants entered the REM sleep phase an average of about 43 minutes earlier after stimulation and spent about 16 minutes longer in that phase. The results were published in the journal Nature Communications. The researchers see the technology primarily as a potential new approach to better study sleep processes and, in the long term, possibly help people with certain sleep or mental health disorders. However, significantly larger studies are still needed for medical application

What Makes the Sleep Patch Special?

NEUSLeeP is a non-invasive system that combines electrophysiological measurements and focused ultrasound in a wearable patch. While conventional systems for examining or influencing deep brain regions often require large devices, NEUSLeeP was designed to be worn directly on the skin during sleep.

The patch features electrodes that, among other things, record EEG signals. This allows researchers to determine which sleep stage a person is in. At the same time, a specially developed ultrasound module generates focused sound waves that can be used to specifically stimulate a deeper brain region.

The study focused on the subthalamic nucleus (STN), a structure located deep within the brain that is part of complex networks and is associated, among other things, with motor control and various functions of the basal ganglia. The researchers suspect that targeted stimulation of this area may influence networks involved in the regulation of REM sleep.

According to the researchers, the device weighs about 103 grams and was specifically designed for overnight use. Its flexible design is intended to conform to the skin and allow it to be worn even while sleeping.

REM Sleep Begins Significantly Earlier

The first study included 28 participants. Based on a standardized sleep questionnaire, 16 participants were classified as healthy sleepers, while 12 participants showed elevated scores for sleep problems. The participants were between 19 and 38 years old.

The study was conducted over two consecutive nights. On the first night, a sham treatment was administered; on the second night, ultrasound stimulation was used. This allowed the researchers to compare changes within the same individuals.

The results were particularly striking with regard to REM sleep. The time until the first occurrence of the REM phase was shortened by a total of about 43 minutes. At the same time, the proportion of REM sleep relative to total sleep time increased by about 4.6 percent, or roughly 16 minutes. These changes were observed in both the healthy participants and the group with sleep problems.

According to the researchers, the stimulation did not fundamentally alter the overall sleep architecture. Sleep stages such as N1, N2, and N3, as well as overall sleep efficiency, showed no significant changes. The number of nighttime awakenings also remained largely unchanged. The results therefore suggest that the stimulation may be able to influence REM sleep in a relatively targeted manner without significantly altering the overall sleep rhythm.

Why is REM Sleep So Important?

REM sleep is the sleep phase during which vivid dreams occur particularly frequently. At the same time, it is far more than just the phase in which we dream. During REM sleep, the brain is active in many ways. Research links this sleep phase, among other things, to the processing of emotional experiences, memory processes, and adaptation to stress.

That is why scientists are increasingly interested in whether changes in REM sleep are also related to mental health. Disturbances in REM sleep are observed in conditions such as depression, anxiety disorders, and post-traumatic stress disorder (PTSD).

However, the new study does not show that prolonging REM sleep automatically treats depression, anxiety disorders, or PTSD. Rather, it provides initial technical evidence that this sleep phase can be specifically influenced using a non-invasive, wearable system.

Evidence of Effects on Stress and Emotional Processing

The researchers therefore did not limit their investigation to sleep itself. In healthy participants, they also observed changes in heart rate variability (HRV) following stimulation. Heart rate variability describes the temporal fluctuations between individual heartbeats. It is often used as a measure of how flexibly the autonomic nervous system can respond to different demands. In the healthy group, HRV increased after stimulation. In contrast, this effect was not clearly evident in participants with sleep problems. In addition, the researchers conducted brain imaging studies following the sleep study. These revealed changes in activity in specific brain regions involved in the processing of emotional stimuli.

These results are interesting but must be interpreted with caution. The study was small and not designed to prove that NEUSLeeP can treat mental health disorders. Gregory Fonzo, one of the co-principal investigators, described REM sleep as an important component of emotional processing and stress adaptation. The researchers therefore hope that specifically influencing this sleep phase could open up new possibilities for treating certain conditions in the future.

No Medication and No Surgery

One potential advantage of the technology is that it does not require medication or surgery. Conventional methods for the targeted stimulation of deep brain regions sometimes involve the use of implanted electrodes. Such procedures can be very precise but involve surgery. NEUSLeeP, on the other hand, takes a non-invasive approach: the ultrasound energy is focused from the outside onto a specific brain region.

In the long term, this could be particularly interesting for applications requiring repeated treatment. At the same time, this very non-invasive stimulation is one of the issues that needs to be examined more closely in future studies.

In the current study, participants reported that the patch was comfortable, and only a few side effects were observed. However, the study was small and lasted only two nights. No conclusions can yet be drawn from this regarding the safety of long-term or regular use.

What the Researchers Still Need to Find Out

The results should therefore be understood primarily as an initial proof of concept. The researchers must now investigate whether the observed effects can be confirmed in larger and more diverse patient groups. Of particular interest is the question of whether a targeted improvement in REM sleep actually leads to long-term health benefits. To answer this, it is not enough to simply show that people enter the REM phase more quickly or remain in it slightly longer.

Future studies must therefore also examine whether this leads to improvements in, for example, sleep quality, daytime well-being, stress management, or certain symptoms of mental health disorders. The team plans further studies, including among people with chronic insomnia, depression, and PTSD. The scientists also see potential applications in at-home sleep monitoring, neuroscientific research, and personalized sleep treatments.

No Ready-Made Sleep Aid from the Patch Yet

As promising as the initial results are, NEUSLeeP should not currently be viewed as a ready-made treatment for sleep disorders. The study included only 28 participants, and the actual sleep intervention was tested over a single night using ultrasound stimulation compared to a placebo condition. It is also not yet fully understood why the stimulation alters REM sleep. The researchers assume that the effect is mediated through complex networks in the brain. However, the exact mechanism is still the subject of further investigation.

Nevertheless, the study shows that modern wearable technologies are increasingly moving beyond simply measuring sleep. In the future, they could potentially also be used to specifically influence certain brain activities during sleep. For people with sleep problems, the device is not yet an available treatment. For sleep research, however, NEUSLeeP represents an interesting new approach—particularly because it combines measurement and targeted stimulation in a single wearable system. Future studies must now determine whether this technical breakthrough can indeed lead to a safe and effective treatment for people with sleep disorders or mental health conditions.