How the brain focuses on what’s in mind

Remembering directions someone just gave you is an example of working memory. In a new study, MIT researchers show that the brain's focus on the contents of what its holding in mind derives from bursts of gamma frequency rhythms in the front of the brain.
Photo credit: George Pak

Working memory, that handy ability to consciously hold and manipulate new information in mind, takes work. In particular, participating neurons in the prefrontal cortex have to work together in synchrony to focus our thoughts, whether we’re remembering a set of directions or tonight’s menu specials. A new study by researchers based at The Picower Institute for Learning and Memory at MIT shows how that focus emerges.

The key measure in the study in Scientific Reports is the variability of the neurons’ activity. Scientists widely agree that less variability activity means more-focused attunement to the task. Measures of that variability have indeed shown that it decreases when humans and animals focus during working memory games in the lab.

In several studies between 2016 and 2018, lead author Mikael Lundqvist and co-senior author Earl K. Miller showed through direct measurements of hundreds of neurons and rigorous modeling that bursts of gamma frequency rhythms in the prefrontal cortex coordinate neural representation of the information held in mind. The information representation can be measured in the synchronized spiking of populations of individual neurons. Bursts of beta frequency rhythms, meanwhile, implement the brain’s manipulation of that information. The theory, which Miller dubbed “Working Memory 2.0” challenged a long-held orthodoxy that neurons maintain working memory information through steady, persistent activity. Proponents of that older model, which emerged from averaged measurements made in relatively few neurons, used computer-based modeling of brain activity to argue that reduced variability cannot emerge from intermittent bursts of rhythmic activity.

New method for comparing neural networks exposes how artificial intelligence works

Researchers at Los Alamos are looking at new ways to compare neural networks. This image was created with an artificial intelligence software called Stable Diffusion, using the prompt “Peeking into the black box of neural networks.”
Source: Los Alamos National Laboratory

A team at Los Alamos National Laboratory has developed a novel approach for comparing neural networks that looks within the “black box” of artificial intelligence to help researchers understand neural network behavior. Neural networks recognize patterns in datasets; they are used everywhere in society, in applications such as virtual assistants, facial recognition systems and self-driving cars.

“The artificial intelligence research community doesn’t necessarily have a complete understanding of what neural networks are doing; they give us good results, but we don’t know how or why,” said Haydn Jones, a researcher in the Advanced Research in Cyber Systems group at Los Alamos. “Our new method does a better job of comparing neural networks, which is a crucial step toward better understanding the mathematics behind AI.”

Jones is the lead author of the paper “If You’ve Trained One You’ve Trained Them All: Inter-Architecture Similarity Increases With Robustness,” which was presented recently at the Conference on Uncertainty in Artificial Intelligence. In addition to studying network similarity, the paper is a crucial step toward characterizing the behavior of robust neural networks.

These pesticides may increase cancer risk in children

Julia Heck, associate research professor of epidemiology
in the UCLA Fielding School of Public Health.
Source: UCLA

Past research has shown that pesticide exposure increases the risk of cancer. Now, UCLA-led research has exposed which specific pesticides increase the risk of retinoblastoma — a rare eye tumor — in children.

The study, published in the August International Journal of Hygiene and Environmental Health, found that children prenatally exposed to the chemicals acephate and bromacil had an increased risk of developing unilateral retinoblastoma, or cancer in one eye, and that exposure to pymetrozine and kresoxim-methyl increased the risk of all types of retinoblastoma.

“What’s important is looking at specific bad actors and identifying them,” said Julia Heck, an adjunct associate professor in the department of epidemiology at the UCLA Fielding School of Public Health, who studies environmental causes of childhood cancers.

Identifying specific pesticides correlated with cancer is the first step toward banning or replacing them with less harmful options.

The researchers studied land use data and pesticide use reports — which provide information on where, when and in what quantity the chemicals are applied — to determine locations of possible pesticide exposure. They considered 132 pesticides that are associated with cancer.

They compared children with retinoblastoma to random children with California birth certificates and found that those with cancer were more likely to have been born in neighborhoods near applications of specific pesticides.

The gene to which we owe our big brain

A section of a brain organoid made from stem cells of a human. In magenta are actively proliferating brain stem cells, in yellow a subset of brain stem cells.
Photo Credit: Jan Fischer

ARHGAP11B - this complex name is given to a gene that is unique to humans and plays an essential role in the development of the neocortex. The neocortex is the part of the brain to which we owe our high mental abilities. A team of researchers from the German Primate Center (DPZ) - Leibniz Institute for Primate Research in Göttingen, the Max Planck Institute for Molecular Cell Biology and Genetics (MPI-CBG) in Dresden, and the Hector Institute for Translational Brain Research (HITBR) in Mannheim has investigated the importance of ARHGAP11B in neocortex development during human evolution. 

To do this, the team introduced for the first time a gene that exists only in humans into laboratory-grown brain organoids from our closest living relatives, chimpanzees. In the chimpanzee brain organoid, the ARHGAP11B gene led to an increase in brain stem cells relevant to brain growth and an increase in those neurons that play a critical role in the extraordinary mental abilities of humans. If, on the other hand, the ARHGAP11B gene was switched off in human brain organoids, the quantity of these brain stem cells fell to the level of a chimpanzee. Thus, the research team was able to show that the ARGHAP11B gene played a crucial role in the evolution of the brain from our ancestors to modern humans.

Insects struggle to adjust to extreme temperatures making them vulnerable to climate change

Cardinal beetle 
Credit: Erik Karits from Pixabay

Insects have weak ability to adjust their thermal limits to high temperatures and are thus more susceptible to global warming than previously thought.

As more frequent and intense heat waves expose animals to temperatures outside of their normal limits, an international team led by researchers at the University of Bristol studied over 100 species of insect to better understand how these changes will likely affect them.

Insects – which are as important as pollinators, crop pests and disease vectors - are particularly vulnerable to extreme temperatures. One-way insects can deal with such extremes is through acclimation, where previous thermal exposure extends their critical thermal limits. Acclimation can trigger physiological changes such as the upregulation of heat shock proteins, and result in changes to phospholipid composition in the cell membrane.

The team discovered that insects struggle to do this effectively, revealing acclimation of both upper and lower critical thermal limits was weak – for each 1°C shift in exposure, limits were adjusted by only 0.092°C and 0.147°C respectively (i.e. only a small compensation of 10 or 15%).

Little Ice Age study reveals North Atlantic reached a tipping point

Ocean quahog clam.
Credit Paul Kay

Scientists have used centuries-old clam shells to see how the North Atlantic climate system reached a "tipping point" before the Little Ice Age.

The Little Ice Age – a period of regional cooling, especially in the North Atlantic – lasted several centuries, ending in about 1850.

A long-standing theory suggests initial cooling in this period was sustained by "sea-ice to ocean feedbacks" – sea ice expanded and this slowed ocean currents which in turn reduced the flow of warm water from the south.

The new study, by the University of Exeter, used the shells of quahog clams – which can live for several hundred years – to understand how the ocean has evolved and responded to external changes over recent centuries.

The findings show that the North Atlantic climate system destabilized and lost resilience (the ability to recover from external changes) prior to the Little Ice Age, possibly causing it to "tip" into a new, colder state.

And the researchers say the North Atlantic could be approaching a new tipping point, with major consequences for the region's climate.

Optical rule was made to be broken

A scanning electron microscope image of an iron pyrite metasurface created at Rice University to test its ability to transcend the Moss rule, which describes a trade-off between a material’s optical absorption and how it refracts light. The research shows potential to improve screens for virtual reality and 3D displays along with optical technologies in general.
Credit: The Naik Lab/Rice University

If you’re going to break a rule with style, make sure everybody sees it. That’s the goal of engineers at Rice University who hope to improve screens for virtual reality, 3D displays and optical technologies in general.

Gururaj Naik, an associate professor of electrical and computer engineering at Rice’s George R. Brown School of Engineering, and Applied Physics Graduate Program alumna Chloe Doiron found a way to manipulate light at the nanoscale that breaks the Moss rule, which describes a trade-off between a material’s optical absorption and how it refracts light.

Apparently, it’s more like a guideline than an actual rule, because a number of “super-Mossian” semiconductors do exist. Fool’s gold, aka iron pyrite, is one of them.

For their study in Advanced Optical Materials, Naik, Doiron and co-author Jacob Khurgin, a professor of electrical and computer engineering at Johns Hopkins University, find iron pyrite works particularly well as a nanophotonic material and could lead to better and thinner displays for wearable devices.

More important is that they’ve established a method for finding materials that surpass the Moss rule and offer useful light-handling properties for displays and sensing applications.

Study finds white children more likely to be overdiagnosed for ADHD

A new study by Professor Paul Morgan finds that white children are more likely to be overdiagnosed for ADHD than children of color.
Photo credit: Ben White on Unsplash

A new study led by Paul Morgan, Harry and Marion Eberly Faculty Fellow and professor of education (educational theory and policy) and demography, and published in the Journal of Learning Disabilities, examines which sociodemographic groups of children are more likely to be overdiagnosed and overtreated for ADHD. The researchers analyzed data from 1,070 U.S. elementary school children who had previously displayed above-average behavioral, academic or executive functioning the year before their initial ADHD diagnoses. The team said those children were considered unlikely to have ADHD by the researchers because children diagnosed and treated for ADHD should displaychronically inattentive, hyperactive or impulsive behaviors that impair their functioning and result in below-average academic or social development.

A problem with ADHD overdiagnosis, Morgan said, is that it contributes to stigma and skepticism toward those experiencing more serious impairments.

“It undermines a confidence in the disorder,” he said. “If anyone can be diagnosed with ADHD, then what is ADHD? For those who have significant impairments, they may experience greater skepticism about the condition. Mental health resources are already scarce, those with serious impairments could lose out.”

Live Intracellular Imaging with New, Conditionally Active Immunofluorescence Probe

Figure 1
Schematic (a) and mechanism (c) of p53 Intra Q-body. (b) p53-dependent fluorescence signal and (d) microscopy images. (a) The double labelled fluorescent dye in the antigen fragment-based Q-body is de-quenched on binding with the target antigen, thus displaying fluorescent signaling for visualizing the intracellular target. (b) p53 peptide concentration-dependent variation in fluorescence signal intensity. (c) Q-body displays a high fluorescent signal on binding with the target in cells expressing p53, as compared to the 'p53' negative human cells. (d) Confocal microscopy images of HCT116 p53 and SK-BR-3. Cells which do not express p53, i.e., HCT116 p53(-/-) exhibit no TAMRA-based fluorescence while others (including images stained with Hoechst dye for illuminating nucleus and under bright-field to show the cells) display significant fluorescence.
Source/Credit: Tokyo Institute of Technology

Furthering the visualization of intracellular dynamics for therapeutic applications, a Tokyo Tech research team has now demonstrated precise imaging of endogenous proteins in live cells using an antigen-binding fragment (Fab)-based Quenchbody (Q-body). The Q-body probe shows antigen-dependent response and a switchable (on-off) fluorescent signaling, enabling the visualization and sorting of cells expressing p53, a tumor suppressor biomarker protein.

Recent advances in imaging technology have made it possible to visualize intracellular dynamics, which offers a better understanding of several key biological principles for accelerating therapeutic development. Fluorescent labeling is one such technique that is used to identify intracellular proteins, their dynamics, and dysfunction. Both internal as well as external probes with fluorescent dyes are used for this purpose, although external probes can better visualize intracellular proteins as compared to the internal probes. However, their application is limited by non-specific binding to intracellular components, resulting in a low target specific signaling and higher background noise.

Simulation helps in the search for the origin of cosmic radiation

The colorful lines show how cosmic radiation is deflected in magnetic fields. The white straight lines represent a large-scale magnetic field. In addition, small-scale magnetic fields not shown here act on the orbits of the particles (colorful lines).
Credit: RUB, Dr. Lukas Merten

The cosmic radiation seems to be all around us. That is exactly what makes it difficult to find their sources. It would be helpful if you could trace your way back through space. A new program helps with this.

An international research team has developed a computer program that can be used to simulate the transport of cosmic radiation through space. The scientists hope to be able to solve the puzzle about the sources of cosmic radiation. So far it is unknown which celestial objects emit the high-energy radiation that patterns the earth from space. In order to be able to explain experimental data, theoretical models are required; the new computer simulation can deliver this. A team of researchers from the Ruhr University Bochum (RUB) describes the software in the journal of Cosmology and Astroparticle Physics, published online on September 12, 2022.

Like a uniformly illuminated sky during the day

Since their discovery of 100 years, researchers have been trying to decipher where the cosmic radiation comes from. The problem: viewed from Earth, it looks like heaven by day with the naked eye: it is illuminated almost everywhere where you look. Because the light of the sun is scattered in the earth's atmosphere and is distributed evenly over the entire sky. Cosmic radiation is also scattered on its way to earth - through interactions with cosmic magnetic fields. Only a uniformly illuminated picture can be seen from the earth; the origin of the radiation remains hidden.