Studies by a growing number of labs have identified neurological health benefits from exposing human volunteers or animal models to light, sound, and/or tactile stimulation at the brain’s “gamma” frequency rhythm of 40Hz. In the latest such research at The Picower Institute for Learning and Memory and Alana Down Syndrome Center at MIT, scientists found that 40Hz sensory stimulation improved cognition and circuit connectivity and encouraged the growth of new neurons in mice genetically engineered to model Down syndrome.

Li-Huei Tsai, Picower Professor at MIT and senior author of the new study in PLOS ONE, says that the results are encouraging, but also cautions that much more work is needed to test whether the method, called GENUS (for gamma entrainment using sensory stimulation), could provide clinical benefits for people with Down syndrome. Her lab has begun a small study with human volunteers at MIT.

“While this work, for the first time, shows beneficial effects of GENUS on Down syndrome using an imperfect mouse model, we need to be cautious, as there is not yet data showing whether this also works in humans,” says Tsai, who directs The Picower Institute and The Alana Center, and is a member of MIT’s Department of Brain and Cognitive Sciences faculty.

Still, she says, the newly published article adds evidence that GENUS can promote a broad-based, restorative, “homeostatic” health response in the brain amid a wide variety of pathologies. Most GENUS studies have addressed Alzheimer’s disease in humans or mice, but others have found benefits from the stimulation for conditions such as “chemo brain” and stroke.

Down syndrome benefits

In the study, the research team led by postdoc Md Rezaul Islam and Brennan Jackson PhD ’23 worked with the commonly used “Ts65Dn” Down syndrome mouse model. The model recapitulates key aspects of the disorder, although it does not exactly mirror the human condition, which is caused by carrying an extra copy of chromosome 21.

In the first set of experiments in the paper, the team shows that an hour a day of 40Hz light and sound exposure for three weeks was associated with significant improvements on three standard short-term memory tests — two involving distinguishing novelty from familiarity and one involving spatial navigation. Because these kinds of memory tasks involve a brain region called the hippocampus, the researchers looked at neural activity there and measured a significant increase in activity indicators among mice that received the GENUS stimulation versus those that did not.

To better understand how stimulated mice could show improved cognition, the researchers examined whether cells in the hippocampus changed how they express their genes. To do this, the team used a technique called single cell RNA sequencing, which provided a readout of how nearly 16,000 individual neurons and other cells transcribed their DNA into RNA, a key step in gene expression. Many of the genes whose expression varied most prominently in neurons between the mice that received stimulation and those that did not were directly related to forming and organizing neural circuit connections called synapses.

To confirm the significance of that finding, the researchers directly examined the hippocampus in stimulated and control mice. They found that in a critical subregion, the dentate gyrus, stimulated mice had significantly more synapses.

Diving deeper

The team not only examined gene expression across individual cells, but also analyzed those data to assess whether there were patterns of coordination across multiple genes. Indeed, they found several such “modules” of co-expression. Some of this evidence further substantiated the idea that 40Hz-stimulated mice made important improvements in synaptic connectivity, but another key finding highlighted a role for TCF4, a key regulator of gene transcription needed for generating new neurons, or “neurogenesis.”  

The team’s analysis of genetic data suggested that TCF4 is underexpressed in Down syndrome mice, but the researchers saw improved TCF4 expression in GENUS-stimulated mice. When the researchers went to the lab bench to determine whether the mice also exhibited a difference in neurogenesis, they found direct evidence that stimulated mice exhibited more than unstimulated mice in the dentate gyrus. These increases in TCF4 expression and neurogenesis are only correlational, the researchers noted, but they hypothesize that the increase in new neurons likely helps explain at least some of the increase in new synapses and improved short-term memory function.

“The increased putative functional synapses in the dentate gyrus is likely related to the increased adult neurogenesis observed in the Down syndrome mice following GENUS treatment,” Islam says.

This study is the first to document that GENUS is associated with increased neurogenesis.

The analysis of gene expression modules also yielded other key insights. One is that a cluster of genes whose expression typically declines with normal aging, and in Alzheimer’s disease, remained at higher expression levels among mice who received 40Hz sensory stimulation.

And the researchers also found evidence that mice that received stimulation retained more cells in the hippocampus that express Reelin. Reelin-expressing neurons are especially vulnerable in Alzheimer’s disease, but expression of the protein is associated with cognitive resilience amid Alzheimer’s disease pathology, which Ts65Dn mice develop. About 90 percent of people with Down syndrome develop Alzheimer’s disease, typically after the age of 40.

“In this study, we found that GENUS enhances the percentage of Reln+ neurons in hippocampus of a mouse model of Down syndrome, suggesting that GENUS may promote cognitive resilience,” Islam says.

Taken together with other studies, Tsai and Islam say, the new results add evidence that GENUS helps to stimulate the brain at the cellular and molecular level to mount a homeostatic response to aberrations caused by disease pathology, be it neurodegeneration in Alzheimer’s, demyelination in chemo brain, or deficits of neurogenesis in Down syndrome.

But the authors also cautioned that the study had limits. Not only is the Ts65Dn model an imperfect reflection of human Down syndrome, but also the mice used were all male. Moreover, the cognitive tests in the study only measured short-term memory. And finally, while the study was novel for extensively examining gene expression in the hippocampus amid GENUS stimulation, it did not look at changes in other cognitively critical brain regions, such as the prefrontal cortex.

In addition to Jackson, Islam, and Tsai, the paper’s other authors are Maeesha Tasnim Naomi, Brooke Schatz, Noah Tan, Mitchell Murdock, Dong Shin Park, Daniela Rodrigues Amorim, Fred Jiang, S. Sebastian Pineda, Chinnakkaruppan Adaikkan, Vanesa Fernandez, Ute Geigenmuller, Rosalind Mott Firenze, Manolis Kellis, and Ed Boyden.

Funding for the study came from the Alana Down Syndrome Center at MIT and the Alana USA Foundation, the U.S. National Science Foundation, the La Caixa Banking Foundation, a European Molecular Biology Organization long-term postdoctoral fellowship, Barbara J. Weedon, Henry E. Singleton, and the Hubolow family.

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Nature Climate Change, Published online: 12 May 2025; doi:10.1038/s41558-025-02334-w

The gap between adaptation policy planning and actual implementation could delay effective actions. Researchers demonstrate why internal consistency checks should be the starting point to reduce the gap by applying them for city-level adaptation plans across Europe.

Nature Climate Change, Published online: 12 May 2025; doi:10.1038/s41558-025-02327-9

The authors assess the risk of overshoot beyond 1.5 °C warming, using three scenarios with minimal overshoot, brief overshoot and sustained overshoot. They show a risk of long-term Amazon dieback, which begins as early as 1.3 °C warming but is largely mitigated by reducing temperature below 1.5 °C.

Encrypted chat apps like Signal and WhatsApp are one of the best ways to keep your digital conversations as private as possible. But if you’re not careful with how those conversations are backed up, you can accidentally undermine your privacy.

When a conversation is properly encrypted end-to-end, it means that the contents of those messages are only viewable by the sender and the recipient. The organization that runs the messaging platform—such as Meta or Signal—does not have access to the contents of the messages. But it does have access to some metadata, like the who, where, and when of a message. Companies have different retention policies around whether they hold onto that information after the message is sent.

What happens after the messages are sent and received is entirely up to the sender and receiver. If you’re having a conversation with someone, you may choose to screenshot that conversation and save that screenshot to your computer’s desktop or phone’s camera roll. You might choose to back up your chat history, either to your personal computer or maybe even to cloud storage (services like Google Drive or iCloud, or to servers run by the application developer).

Those backups do not necessarily have the same type of encryption protections as the chats themselves, and may make those conversations—which were sent with strong, privacy-protecting end-to-end encryption—available to read by whoever runs the cloud storage platform you’re backing up to, which also means they could hand them at the request of law enforcement.

With that in mind, let’s take a look at how several of the most popular chat apps handle backups, and what options you may have to strengthen the security of those backups.

How Signal Handles Backups

The official Signal app doesn’t offer any way to back up your messages to a cloud server (some alternate versions of the app may provide this, but we recommend you avoid those, as there don’t exist any alternatives with the same level of security as the official app). Even if you use a device backup, like Apple’s iCloud backup, the contents of Signal messages are not included in those.

Instead, Signal supports a manual backup and restore option. Basically, messages are not backed up to any cloud storage, and Signal cannot access them, so the only way to transfer messages from one device to another is manually through a process that Signal details here. If you lose your phone or it breaks, you will likely not be able to transfer your messages.

How WhatsApp Handles Backups

WhatsApp can optionally back up the contents of chats to either a Google Account on Android, or iCloud on iPhone, and you have a choice to back up with or without end-to-end encryption. Here are directions for enabling end-to-end encryption in those backups. When you do so, you’ll need to create a password or save a 64-digit key.

How Apple’s iMessages Handles Backups

Communication between people with Apple devices using Apple’s iMessage (blue bubbles in the Messages app), are end-to-end encrypted, but the backups of those conversations are not end-to-end encrypted by default. This is a loophole we’ve routinely demanded Apple close.

The good news is that with the release of the Advanced Data Protection feature, you can optionally turn on end-to-end encryption for almost everything stored in iCloud, including those backups (unless you’re in the U.K., where Apple is currently arguing with the government over demands to access data in the cloud, and has pulled the feature for U.K. users).

How Google Messages Handles Backups

Similar to Apple iMessages, Google Messages conversations are end-to-end encrypted only with other Google Messages users (you’ll know it’s enabled when there’s a small lock icon next to the send button in a chat).

You can optionally back up Google Messages to a Google Account, and as long as you have a passcode or lock screen password, the backup of the text of those conversations is end-to-end encrypted. A feature to turn on end-to-end encrypted backups directly in the Google Messages app, similar to how WhatsApp handles it, was spotted in beta last year but hasn’t been officially announced or released.

Everyone in the Group Chat Needs to Get Encrypted

Note that even if you take the extra step to turn on end-to-end encryption, everyone else you converse with would have to do the same to protect their own backups. If you have particularly sensitive conversations on apps like WhatsApp or Apple Messages, where those encrypted backups are an option but not the default, you may want to ask those participants to either not back up their chats at all, or turn on end-to-end encrypted backups. 

Ask Yourself: Do I Need Backups Of These Conversations?

Of course, there’s a reason people want to back up their conversations. Maybe you want to keep a record of the first time you messaged your partner, or want to be able to look back on chats with friends and family. There should not be a privacy trade-off for those who want to save those conversations, but unfortunately you do need to weigh whether or not it’s worth saving your chats with the potential of them being exposed in your security plan.

But also it’s worth considering that we don’t typically need every conversation we have stored forever. Many chat apps, including WhatsApp and Signal, offer some form of “disappearing messages,” which is a way to delete messages after a certain amount of time. This gets a little tricky with backups in WhatsApp. If you create a backup before a message disappears, it’ll be included in the backup, but deleted when you restore later. Those messages will remain there until you back up again, which may be the next day, or may not be many days, if you don’t connect to Wi-Fi.

You can change these disappearing messaging settings on a per-conversation basis. That means you can choose to set the meme-friendly group chat with your friends to delete after a week, but retain the messages with your kids forever. Google Messages and Apple Messages don’t offer any such feature—but they should, because it’s a simple way to protect our conversations that gives more control over to the people using the app.

End-to-end encrypted chat apps are a wonderful tool for communicating safely and privately, but backups are always going to be a contentious part of how they work. Signal’s approach of not offering cloud storage for backups at all is useful for those who need that level of privacy, but is not going to work for everyone’s needs. Better defaults and end-to-end encrypted backups as the only option when cloud storage is offered would be a step forward, and a much easier solution than going through and asking every one of your contacts how or if they back up their chats.

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The video is really amazing.

As usual, you can also use this squid post to talk about the security stories in the news that I haven’t covered.

This interview is part of a series of short interviews from the MIT Department of Electrical Engineering and Computer Science, called Student Spotlights. Each spotlight features a student answering their choice of questions about themselves and life at MIT. Today’s interviewee, Aria Eppinger ’24, graduated with her undergraduate degree in Course 6-7 (Computer Science and Molecular Biology) last spring. This spring, she will complete her MEng in 6-7. Her thesis, supervised by Ford Professor of Engineering Doug Lauffenburger in the Department of Biological Engineering, investigates the biological underpinnings of adverse pregnancy outcomes, including preterm birth and preeclampsia, by applying polytope-fitting algorithms.

Q: Tell us about one teacher from your past who had an influence on the person you’ve become. 

A: There are many teachers who had a large impact on my trajectory. I would first like to thank my elementary and middle school teachers for imbuing in me a love of learning. I would also like to thank my high school teachers for not only teaching me the foundations of writing strong arguments, programming, and designing experiments, but also instilling in me the importance of being a balanced person. It can be tempting to be ruled by studies or work, especially when learning and working are so fun. My high school teachers encouraged me to pursue my hobbies, make memories with friends, and spend time with family. As life continues to be hectic, I’m so grateful for this lesson (even if I’m still working on mastering it).

Q: Describe one conversation that changed the trajectory of your life.

A: A number of years ago, I had the opportunity to chat with Warren Buffett. I was nervous at first, but soon put to ease by his descriptions of his favorite foods — hamburgers, French fries, and ice cream — and his hitchhiking stories. His kindness impressed and inspired me, which is something I carry with me and aim to emulate all these years later.

Q: Do you have any pets?

A: I have one dog who lives at home with my parents. Dodger, named after “Artful Dodger” in Oliver Twist, is as mischievous as beagles tend to be. We adopted him from a rescue shelter when I was in elementary school. 

Q: Are you a re-reader or a re-watcher — and if so, what are your comfort books, shows, or movies?

A: I don’t re-read many books or re-watch many movies, but I never tire of Jane Austen’s “Pride and Prejudice.” I bought myself an ornately bound copy when I was interning in New York City last summer. Austen’s other novels, especially “Sense and Sensibility,” “Persuasion,” and “Emma,” are also favorites, and I’ve seen a fair number of their movie and miniseries adaptations. My favorite adaptation is the 1995 BBC production of “Pride and Prejudice” because of the cohesion with the original book and the casting of the leads, as well as the touches and plot derivations added by the producer and director to bring the work to modern audiences. The adaptation is quite long, but I have fond memories of re-watching it with some fellow Austinites at MIT.

Q: If you had to teach a really in-depth class about one niche topic, what would you pick?

A: There are two types of people in the world: those who eat to live, and those who live to eat. As one of the latter, I would have to teach some sort of in-depth class on food. Perhaps I would teach the science behind baking chocolate cake, or churning the perfect ice cream. Or maybe I would teach the biochemistry of digesting. In any case, I would have to have lots of hands-on demos and reserve plenty for taste-testing!

Q: What was the last thing you changed your mind about?

A: Brisket! I never was a big fan of brisket until I went to a Texas BBQ restaurant near campus, The Smoke Shop BBQ. Growing up, I had never had true BBQ, so I was quite skeptical. However, I enjoyed not only the brisket but also the other dishes. The Brussels sprouts with caramelized onions is probably my favorite dish, but it feels like a crime to say that about a BBQ place!

Q: What are you looking forward to about life after graduation? What do you think you’ll miss about MIT? 

A: I’m looking forward to new adventures after graduation, including working in New York City and traveling to new places. I cross-registered to take Intensive Italian at Harvard this semester and am planning a trip to Italy to practice my Italian, see the historic sites, visit the Vatican, and taste the food. Non vedo l’ora di viaggiare all’Italia! [I can't wait to travel to Italy!]

While I’m excited for what lies ahead, I will miss MIT. What a joy it is to spend most of the day learning information from a fire hose, taking a class on a foreign topic because the course catalog description looked fun, talking to people whose viewpoint is very similar or very different from my own, and making friends that will last a lifetime.

MIT faculty and researchers receive many external awards throughout the year. The MIT School of Engineering periodically highlights the honors, prizes, and medals won by community members working in academic departments, labs, and centers. Winter 2025 honorees include the following:

• Faez Ahmed, the American Bureau of Shipping Career Development Professor in Naval Engineering and Utilization and an assistant professor in the Department of Mechanical Engineering (MechE), received a 2024 National Science Foundation (NSF) CAREER Award. The CAREER program is one of NSF’s most prestigious awards that supports early-career faculty who display outstanding research, excellent education, and the integration of education and research.
   
• Martin Zdenek Bazant, the E.G. Roos (1944) Professor in the Department of Chemical Engineering (ChemE), was elected to the National Academy of Engineering (NAE). Membership in the NAE is awarded to individuals who have made outstanding contributions to “engineering research, practice, or education.”
   
• Angela Belcher, the James Mason Crafts Professor in the Department of Biological Engineering and the Department of Materials Science and Engineering (DMSE), received the National Medal of Science. The award is the nation’s highest honor for scientists and innovators.
   
• Moshe E. Ben-Akiva, the Edmund K. Turner Professor in Civil Engineering, was elected to the National Academy of Engineering. Membership in the NAE is given to individuals who have made outstanding contributions to “engineering research, practice, or education.”
   
• Emery Brown, the Edward Hood Taplin Professor of Medical Engineering, received the National Medal of Science. The award is the nation’s highest honor for scientists and innovators.
   
• Charles L. Cooney, professor emeritus of the Department of ChemE, was elected to the National Academy of Engineering. Membership in the NAE is given to individuals who have made outstanding contributions to “engineering research, practice, or education.”
   
• Yoel Fink, the Danae and Vasilis (1961) Salapatas Professor in the DMSE, was elected to the National Academy of Engineering. Membership in the NAE is given to individuals who have made outstanding contributions to “engineering research, practice, or education.”
   
• James Fujimoto, the Elihu Thomson Professor in the Department of Electrical Engineering and Computer Science (EECS), is a 2025 inductee into the National Inventors Hall of Fame. Inductees are patent-holding inventors whose work has made all our lives easier, safer, healthier, and more fulfilling.
   
• Mohsen Ghaffari, an associate professor in the Department of EECS, received a 2025 Sloan Research Fellowship. The fellowship honors exceptional researchers at U.S. and Canadian educational institutions, whose creativity, innovation, and research accomplishments make them stand out as the next generation of leaders.
   
• Marzyeh Ghassemi, the Germeshausen Career Development Professor and associate professor in the Department of EECS and the Institute for Medical Engineering and Science, received a 2025 Sloan Research Fellowship. The fellowships honor exceptional researchers at US and Canadian educational institutions, whose creativity, innovation, and research accomplishments make them stand out as the next generation of leaders.
   
• Linda Griffith, the School of Engineering Professor of Teaching Innovation in the Department of Biological Engineering, received the 2025 BMES Robert A. Pritzker Distinguished Lectureship Award. The award is given to individuals who have demonstrated impactful leadership and accomplishments in biomedical engineering science and practice.
   
• Paula Hammond, MIT’s vice provost for faculty and an Institute Professor in the Department of ChemE, received the National Medal of Technology and Innovation. The award is the nation’s highest honor for scientists and innovators.
   
• Kuikui Liu, the Elting Morison Career Development Professor and an assistant professor in the Department of EECS, received the 2025 Michael and Sheila Held Prize. The award is presented annually to honor outstanding, innovative, creative, and influential research in combinatorial and discrete optimization or related parts of computer science, such as the design and analysis of algorithms and complexity theory.
   
• Farnaz Niroui, an associate professor in the Department of EECS, received a DARPA Innovation Fellowship. The highly selective program chooses fellows to develop and manage a portfolio of high-impact, exploratory research efforts to help identify breakthrough technologies for the U.S. Department of Defense.
   
• Tomás Lozano-Pérez, the School of Engineering Professor of Teaching Excellence in the Department of EECS, was elected to the National Academy of Engineering. Membership in the NAE is given to individuals who have made outstanding contributions to “engineering research, practice, or education.”
   
• Kristala L. Prather, the Arthur Dehon Little Professor and head of the Department of ChemE, was elected to the National Academy of Engineering. Membership in the NAE is given to individuals who have made outstanding contributions to “engineering research, practice, or education.”
   
• Frances Ross, the TDK Professor in DMSE, received the Joseph F. Keithley Award for Advances in Measurement Science. The award recognizes physicists who have been instrumental in developing measurement techniques or equipment that have impacted the physics community by providing better measurements.
   
• Henry “Hank” Smith, the Joseph F. and Nancy P. Keithley Professor of Electrical Engineering Emeritus in the Department of EECS, received the SPIE Frits Zernike Award for Microlithography. The award is presented for outstanding accomplishments in microlithographic technology, especially those furthering the development of semiconductor lithographic imaging and patterning solutions.
   
• Eric Swanson, research affiliate at the Research Laboratory of Electronics, was elected to the National Academy of Engineering. Membership in the NAE is given to individuals who have made outstanding contributions to “engineering research, practice, or education.”
   
• Evelyn N. Wang, MIT's vice president for energy and climate and Ford Professor of Engineering in the Department of MechE, was elected to the National Academy of Engineering. Membership in the NAE is given to individuals who have made outstanding contributions to “engineering research, practice, or education.”
   
• Bilge Yildiz, the Breene M. Kerr (1951) Professor in the Department of Nuclear Science and Engineering and the DMSE, received the Faraday Medal. The award is given to individuals for notable scientific or industrial achievement in engineering or for conspicuous service rendered to the advancement of science, engineering, and technology.
   
• Feng Zhang, the James and Patricia Poitras Professor of Neuroscience and professor of brain and cognitive sciences and biological engineering, received the National Medal of Technology and Innovation. The award is the nation’s highest honor for scientists and innovators.

The Hospital Preparedness Program helps hospitals and emergency managers save lives in wildfires, tornadoes, pandemics and other mass-casualty events.

Critics say the investment in climate-cooling research, like refreezing sea ice and brightening clouds, distracts from the need to cut planet-warming emissions.