Saturday Citations: Neurology of boring sounds; one huge croc; Travels With Sol

14 Mar 2026, 13:00 by Chris Packham

Chris Packham

staff contributor

Meet our staff & contributors
Learn about our editorial standards

Gaby Clark

scientific editor

Meet our editorial team
Behind our editorial process

Robert Egan

associate editor

Meet our editorial team
Behind our editorial process
Editors' notes

This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility:

fact-checked

trusted source

proofread

The GIST
Add as preferred source

Researchers led by the University of Iowa have described and named a new crocodile species that roamed a region in Africa more than 3 million years ago. The species is named Lucy's hunter, because it overlapped with the famed Lucy and her hominin kin and would have hunted them. Credit: Tyler Stone, University of Iowa

The More You Know: This week, researchers successfully reconstructed videos from the brain activity of mice. According to a new study, female birds are more likely to sing when their extended families help with childcare. And mathematicians have disproven a decades-old classical geometry rule by constructing two compact, self-contained torus objects that have the same metric and mean curvature but are structurally different on a global scale. So that's neat.

Additionally: scientists have determined how the brain filters out normal sounds in familiar environments; the sun moved to its current position from the inner galaxy with a bunch of nearly identical stars; and paleontologists have identified a massive new crocodile species that would definitely have feasted on our ancestors 3.2 million years ago.

Brain filters boring sounds

Humans gradually become accustomed to the normal sounds in a familiar environment through neural processes that, although poorly understood, are called habituation. Over time, people gradually begin ignoring normal, nonthreatening stimuli, like a humming refrigerator compressor, in order to focus on novel sounds, like a roaring bear or a pompadoured 1950s miscreant gunning the engine of a hot rod. To understand the neural underpinnings of habituation, researchers at the University of North Carolina Chapel Hill conducted a study with mice to explore two theories.

Predictive filtering theory suggests that the brain learns to predict the occurrence of regularly experienced sounds. Researchers hypothesize that this occurs when higher brain areas—specifically, the orbitofrontal cortex—send signals to brain regions that process sensory signaling, prompting them to cancel out familiar noise. The second theory, called novelty amplification theory, holds that new stimuli prompt additional brain activity that gradually fades over time with exposure.

In their experiments with mice, the researchers found that suppressing the orbitofrontal cortex reversed habituation processes, confirming its role in filtering expected sounds. The authors write, "After daily sound exposure, neural habituation in the primary auditory cortex (A1) was reversed by inactivating the OFC. Top-down projections from the OFC, but not other frontal areas, carried predictive signals that grew with daily sound experience and suppressed A1 via somatostatin-expressing inhibitory neurons. Thus, prediction signals from the OFC cancel out anticipated stimuli by generating their 'negative images' in sensory cortices."

The migratory sun

By creating an accurate catalog of stars and their properties using data from the European Space Agency's Gaia satellite, researchers found evidence that the sun was part of a mass migration of highly similar stars from the core regions of the Milky Way 4 to 6 billion years ago. This poses a problem for astronomers, who have noted an unfathomably large bar structure at the galactic center that creates a "corotation barrier" preventing stars from escaping to the outer galaxy.

Using ESA's data, they compiled a catalog of about 6,500 stellar twins. They calculated the ages of these stars and noticed within the distribution a peak for stars around 4 to 6 billion years old, including the sun, which are now positioned around the same distance from the galactic center. This places the sun squarely among a large migration of highly similar stars. The researchers hypothesize that these stars formed around the same time as the so-called corotation barrier and were able to migrate before it became a galactic gatekeeper, and could therefore suggest a timeline for the evolution of the Milky Way to the state we presently observe.

Discover the latest in science, tech, and space with over 100,000 subscribers who rely on Phys.org for daily insights. Sign up for our free newsletter and get updates on breakthroughs, innovations, and research that matter—daily or weekly.

Croc shock

Lucy is an early australopithecine hominid whom we know from a jumble of fossilized bones discovered in Ethiopia in 1974. She is believed to have lived in deciduous woodlands 3.2 million years ago, and her species adapted over millennia to multiple climates. What was her life like? Did she have a lot of friends? Did she eat fermented fruit to get intoxicated, like modern chimpanzees? Did she, as a group of researchers at the University of Iowa explicitly suggests, have to dodge a gigantic crocodile with a prominent hump on its snout?

Remains of these crocodiles have been unearthed over the years, residing in an Ethiopian museum since their discovery, and Professor Christopher Brochu first studied them in 2016. Now, he and his team have categorized it as a new species and named it Crocodylus lucivenator, meaning "Lucy's hunter." The crocodile ranged from 12 to 15 feet and would have weighed from 600 to 1,300 pounds. Its dominance of the Hadar region's food chain is evidenced by the absence of any other crocodile species.

Brochu says, "It was the largest predator in that ecosystem, more so than lions and hyenas, and the biggest threat to our ancestors who lived there during that time. It's a near certainty this crocodile would have hunted Lucy's species. Whether a particular crocodile tried to grab Lucy, we'll never know, but it would have seen Lucy's kind and thought, 'dinner.'"

Written for you by our author Chris Packham, edited by Gaby Clark, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.