One of the most-viewed PNAS articles in the last week is “Locus coeruleus–amygdala circuit disrupts prefrontal control to impair fear extinction.” Explore the article here: https://ow.ly/yFH250Ywubb.
Stress undermines extinction learning and hinders exposure-based clinical therapies for a variety of neuropsychiatric disorders. In both animals and humans, dysfunction in the ventromedial prefrontal cortex (vmPFC) contributes to stress-impaired extinction, but the neural circuit by which stress modulates vmPFC function is not known. We hypothesize that locus coeruleus (LC) norepinephrine undermines extinction learning by recruiting projections from the basolateral amygdala (BLA) to vmPFC. Using a combination of circuit-specific chemogenetics and calcium imaging, we find that activation of LC noradrenergic neurons mimics a behavioral stressor (footshock), induces freezing behavior, reduces spontaneous neuronal activity in the vmPFC, impairs extinction learning, and alters the population dynamics of vmPFC ensembles.
There’s more evidence that water once flowed on Mars with the discovery of an ancient river delta deep below the surface. NASA’s Perseverance rover found it more than 35 meters beneath Jezero Crater using ground-penetrating radar. Perseverance was launched in 2020 to search for signs of ancient life on the red planet. Since landing in February 2021, it has been exploring Jezero Crater and collecting rock samples.
The crater, which is approximately 45 kilometers (28 miles) in diameter, lies north of the Martian equator and was formed by an asteroid impact almost 4 billion years ago. NASA chose this spot to explore because numerous geological features suggest that water once flowed here and may have supported ancient life, specifically, a part of the crater called the Margin Unit. This area is packed with carbonates, which on Earth, usually form in stable aqueous environments, such as shallow seas or lakebeds.
The new research is published in the journal Science Advances and is based on data from 78 traverses of the area from September 2023 to February 2024.
Does the universe need observers to exist? Neil deGrasse Tyson and co-hosts Chuck Nice and Gary O’Reilly explore questions about entropy, spontaneous symmetry breaking, spectroscopy and more with astrophysicist Charles Liu.
Does the universe require observers for information to exist? From Niels Bohr and the Copenhagen interpretation to modern neuroscience and philosophy, the crew explores whether measurement creates reality or reveals it. How does the double-slit experiment fit into this? Are wave and particle behaviors determined by how we measure them?
The conversation turns to information itself. What do physicists mean by “information”? How is entropy connected to hidden information in a system? We discuss entropy through everyday examples like coin flips, burning wood, and boiling water. How does this relate to quantum computing? We explore how astronomers separate cosmic redshift from stellar motion using spectroscopy, how interstellar dust and extinction curves complicate observations, and why mapping that dust is both a challenge and a source of discovery.
We discuss why the Big Bang didn’t form a black hole, how spontaneous symmetry breaking may have split the fundamental forces, and whether science can meaningfully investigate the universe’s earliest moments. Wrapping up, the team looks ahead to multi-messenger astronomy, next-generation telescope technology, exotic ideas about the speed of light, and how information continues to reshape what we know about the cosmos.
Thanks to our Patrons Avery Ellis, Markus Riegler, Linda Tullberg, Gami Lannin, Arief Aziz, Ron Lawhon, Corie Prater, Patrick McNaught, FracturedEquality, Spengler, Peter Harbeson, Oddron86, Hudson Lowe, Drew Romaniak, V2022, Kyle Ferchen, Branko Denčić, Patrick Borgquist, DJ Sipe, Andy Blair, Alan Keizer, SR, Nihat Cubukcu, Greg Lance, Diwas Pandit, Anik Kasumi, Alexander Albert, Kodai, Dyonne Peters Lewoc AKA DPTaterTot, Adrian, Ben Goff, Jose Barreiro, Saurabh Chaudhari, Wimberley Children’s House, Jean Arthur Deda, Jerrel Thomas, Serkan Ergenc, Douglas Kennedy, Lee Browner, Manuel Palmer, Dans Jansons, Russell Harvey, BladiX, Lars-Ove Torstensson, Norman Weizer, Arian Farkhoy, S. Madge, Pavel Seraphimov, Amanda Wolfe, Heisenberg, Mattchew Phillips, Caleb Berumen, Sretooh, Gary Tabbert, Oscar Abreu Lamas, Kevin Attebury, Volker Haberlandt, SeaGolly, B. Shoemaker, Ruben Ferrer, Steven Adams, Daniel Hintz, Nathaniel Richardson, Nick Griffiths, Adam Schmidt, Scott Plummer, Northernlight, JoMama, Beth, Frank Cottone, Yinj, Betty Anderson, Paul Smith, John Little, Emad Uddin, Brian O’Brien, Jayden Moffatt, Kevin Mace, Zara DeBresoc, Rain Bresee, Mara (Farmstrong), Rose, Stiven, Demethius Jackson, Alejandro Rodriguez, J Davis, Chris Buhler, Nathan Davieau, Sourav Prakash Patra, Wayne Rasmussen, John from Bavaria, Stephanie Phillips, Yohojones, Josh Farrell, John, Oo-De-Lally, Millie Richter, Montague Films, Lawrey Goodrick, and John Giovannettone for supporting us this week.
Nanotechnology is moving from the realm of science fiction to reality, and in the process, these tiny technologies are offering giant opportunities.
Watch my exclusive video The Fermi Paradox: Air https://nebula.tv/videos/isaacarthur–… Nebula using my link for 40% off an annual subscription: https://go.nebula.tv/isaacarthur Credits: Nanotechnology: The Future of Everything Episode 481a; January 12, 2025 Produced, Narrated & Written: Isaac Arthur Select imagery/video supplied by Getty Images Music Courtesy of Epidemic Sound http://epidemicsound.com/creator Stellardrone, “In Time”, “Red Giant” Aerium, featuring Sieger, “Deiljocht“ Get Nebula using my link for 40% off an annual subscription: https://go.nebula.tv/isaacarthur.
Credits: Nanotechnology: The Future of Everything. Episode 481a; January 12, 2025 Produced, Narrated & Written: Isaac Arthur. Select imagery/video supplied by Getty Images. Music Courtesy of Epidemic Sound http://epidemicsound.com/creator. Stellardrone, \
From abiogenesis to AI, we rank the top Great Filter candidates and test them against the data to see which best explains the Fermi Paradox. Is the universe empty, or just dangerous? We explore ten filters—cosmic, biological, and civilizational—that could silence civilizations before they spread.
Visit our Website: http://www.isaacarthur.net Join Nebula: https://go.nebula.tv/isaacarthur Support us on Patreon: / isaacarthur Support us on Subscribestar: https://www.subscribestar.com/isaac-a… Group: / 1,583,992,725,237,264 Reddit: / isaacarthur Twitter: / isaac_a_arthur on Twitter and RT our future content. SFIA Discord Server: / discord . Credits: Could We Accidentally Destroy the Universe? Written, Produced & Narrated by: Isaac Arthur Select imagery/video supplied by Getty Images Music Courtesy of Epidemic Sound http://epidemicsound.com/creator.
Chapters 0:00 Intro 5:08 #10 The Fine-Tuned Universe & Rare Earth 12:55 #9 Abiogenesis (The Origin of Life) 16:29 #8 Complex Cells & Eukaryotes 20:14 #7 Multicellularity and Specialization 22:39 #6 Sexual Reproduction & Genetic Innovation 23:54 #5 Complex Animal Life 25:24 Curiosity 26:39 #4 Extended Childhood & Cooperative Rearing 29:17 #3 Long-Term Climate Stability 31:40 #2 Intelligence That Produces Technology 35:11 #1 The Late Filters: Surviving Technology, Ourselves, and Expanding Beyond the Home System.
Wildlife populations that become small and isolated, often due to habitat loss, inevitably experience inbreeding which can lead to the loss of fitness and eventual extinction. One solution is to perform a genetic rescue: a management intervention where new blood is brought in by introducing outsiders to a population to reduce inbreeding and restore diversity. But how do researchers know the inbreeding problem has been solved?
A new long-term study from Western, led by biology professor and chair David Coltman, shows DNA-based tools detected changes in inbreeding more accurately than traditional pedigree methods in a wild population of bighorn sheep that was recently genetically rescued. The study was published in the journal Evolutionary Applications.
Pedigree approaches estimate genetic health from family history, whereas genomic approaches directly analyze DNA.
The temptation is to treat Moltbook-like systems as harmless curiosities, a kind of accelerated chatroom in which agents talk, play, and occasionally generate entertaining artifacts. That framing is historically consistent with how societies first encountered earlier general-purpose technologies. It is also a mistake. Over time, social networks for AI could come to function as unsupervised training grounds, coordination substrates, and selection environments. AI agents could amplify capabilities through mutual tutoring, tool sharing, and rapid iterative refinement. They could also amplify risks through emergent collusion, deception, and the creation of machine-native memes optimized not for human comprehension but for agent persuasion and control. Such a social network is, therefore, not merely a communication system. It is an engine for cultural evolution. If the participants are AIs, then the culture that evolves could well become both alien and strategically consequential.
To understand what could go wrong, it is helpful to separate near-term societal hazards from longer-term existential hazards, and then to note that Moltbook-like platforms blur the boundary between the two. The near-term hazards include influence operations, economic manipulation, cyber offense, and institutional destabilization. The longer-term hazards derive from the classic AI control problem: How humanity can remain safely in control while benefiting from a superior form of intelligence.
The critical point: AI social networks are not merely places where AIs interact. They are environments in which agents can compound their capabilities and coordinate at scale—and environments in which humans can lose control. The prudent response is to regulate these platforms more like critical infrastructure, prioritizing auditability and reversibility, including the ability to revoke permissions and freeze or roll back agent populations.
Meet the caretaker AIs: guardians of planets, habitats, and civilizations. What happens when machines become the spirit and soul of the worlds they protect?
Grab one of our new SFIA mugs and make your morning coffee a little more futuristic — available now on our Fourthwall store! https://isaac-arthur-shop.fourthwall…
Visit our Website: http://www.isaacarthur.net. Join Nebula: https://go.nebula.tv/isaacarthur. Support us on Patreon: / isaacarthur. Support us on Subscribestar: https://www.subscribestar.com/isaac-a… Facebook Group: / 1583992725237264 Reddit: / isaacarthur. Twitter: / isaac_a_arthur on Twitter and RT our future content. SFIA Discord Server: / discord. Credits: Caretaker AI & Genus Loci 2025 Edition. Written, Produced & Narrated by: Isaac Arthur. Editors: Ludwig Luska. Graphics: Bryan Versteeg. Jeremy Jozwik. Ken York YD Visual. Kris Holland Mafic Studios. Select imagery/video supplied by Getty Images. Music Courtesy of Epidemic Sound http://epidemicsound.com/creator
A bright new lunar crater detected in spacecraft images shows that asteroid impacts continue to reshape the Moon’s surface today. The Moon’s familiar surface tells a story of both ancient violence and ongoing change. While its vast dark basins formed during a period of intense bombardment billion
Images from NASA’s DART mission revealed the first direct evidence that asteroids in a binary system can exchange rocks and dust. Slow moving debris from the asteroid Didymos appears to have struck its moon Dimorphos, leaving distinctive streaks scientists describe as “cosmic snowballs.” Around 1
