A team of researchers from the Keck School of Medicine of USC have now begun to document the actual impact of electric vehicle adoption in the first study to use real-world data to link electric cars, air pollution and health. Leveraging publicly available datasets, the researchers analyzed a “natural experiment” occurring in California as residents in the state rapidly transitioned to electric cars, or light-duty zero emissions vehicles (ZEVs). The results were just published in the journal Science of the Total Environment.

The team compared data on total ZEV registration, air pollution levels and asthma-related emergency room visits across the state between 2013 to 2019. As ZEV adoption increased within a given zip code, local air pollution levels and emergency room visits dropped.

“When we think about the actions related to climate change, often it’s on a global level,” said Erika Garcia, PhD, MPH, an assistant professor of population and public health sciences at the Keck School of Medicine and the study’s lead author. “But the idea that changes being made at the local level can improve the health of your own community could be a powerful message to the public and to policy makers.”

The researchers also found that while total ZEVs increased over time, adoption was considerably slower in low-resource zip codes — what the researchers refer to as the “adoption gap.” That disparity points to an opportunity to restore environmental justice in communities that are disproportionately affected by pollution and related health problems.

“The impacts of climate change on health can be challenging to talk about because they can feel very scary,” said Sandrah Eckel, PhD, an associate professor of population and public health sciences at the Keck School of Medicine and the study’s senior author. “We’re excited about shifting the conversation towards climate change mitigation and adaptation, and these results suggest that transitioning to ZEVs is a key piece of that.”

Benefits for health and the climate

To study the effects of electric vehicle adoption, the research team analyzed and compared four different datasets. First, they obtained data on ZEVs (which includes battery electric, plug-in hybrid, and hydrogen fuel cell cars) from the California Department of Motor Vehicles and tabulated the total number registered in each zip code for every year between 2013 and 2019.

They also obtained data from U.S. Environmental Protection Agency air monitoring sites on levels of nitrogen dioxide (NO₂), an air pollutant related to traffic, and zip code level asthma-related visits to the emergency room. Asthma is one of the health concerns long linked with air pollutants such as NO₂, which can also cause and exacerbate other respiratory diseases, as well as problems with the heart, brain and other organ systems.

Finally, the researchers calculated the percentage of adults in each zip code who held bachelor’s degrees. Educational attainment levels are frequently used as an indicator of a neighborhood’s socioeconomic status.

At the zip code level, for every additional 20 ZEVs per 1,000 people, there was a 3.2% drop in the rate of asthma-related emergency visits and a small suggestive reduction in NO₂ levels. On average across zip codes in the state, ZEVs increased from 1.4 to 14.6 per 1,000 people between 2013 and 2019. ZEV adoption was significantly lower in zip codes with lower levels of educational attainment. For example, a zip code with 17% of the population having a bachelor’s degree had, on average, an annual increase of 0.70 ZEVs per 1,000 people compared to an annual increase of 3.6 ZEVs per 1,000 people for a zip code with 47% of the population having a bachelor’s degree.

Past research has shown that underserved communities, such as lower-income neighborhoods, tend to face worse pollution and associated respiratory problems than more affluent areas. If ZEVs replace gas-powered cars in those neighborhoods, they could stand to benefit substantially.

“Should continuing research support our findings, we want to make sure that those communities that are overburdened with the traffic-related air pollution are truly benefiting from this climate mitigation effort,” Garcia said.

More to learn

While climate change is a massive health threat, mitigating it offers a massive public health opportunity, Eckel said. As one of the first studies to quantify the real-world environmental and health benefits of ZEVs, the research can help demonstrate the power of this mitigation measure, including possibly reduced health care utilization and expenditures.

The findings are promising, Garcia said, but many questions remain. Future studies should consider additional impacts of ZEVs, including emissions related to brake and tire wear, mining of materials for their manufacture, and disposal of old cars. The researchers also hope to study additional types of pollutants and other classes of vehicles, in addition to conducting a follow-up study of the effects of the ever-growing share of ZEVs in the state.

Moving forward, transitioning to ZEVs is just one part of the solution, Eckel said. Shifting to public transport and active transport, including walking and biking, are other key ways to boost environmental and public health.

This work was supported by the University of Southern California Office of Research Strategic Directions for Research Award and the National Institute of Environmental Health Sciences [P30ES007048, P2CES033433].

The authors of the study are Rut Sánchez-Bragado and Josep Lluís Araus-Ortega, from the UB Faculty of Biology and Agrotecnio-UdL; Gustavo A. Slafer, ICREA researcher at the UdL School of Agrifood and Forestry Science and Engineering, and Gemma Molero, from the International Maize and Wheat Improvement Center in Mexico, currently a researcher at KWS Seeds Inc.

A cereal that changed human history

The cultivation of wheat — a grass that became basic food — represented a turning point in the progress of human civilisation. Today it is the world’s most important crop in terms of food security, but EU data warn that the impact of climate change could significantly increase its price and modify its production process in certain areas of the world.

Throughout the domestication process of wheat, the plant phenotype has undergone both rapid (within a few hundred years) and slow (thousands of years) changes, such as the weakening of the rachis, the increase in seed size, and the reduction or disappearance of the awns. In particular, awned and awnless wheat varieties are found all over the world, although the latter tend to be abundant in regions with arid climates, especially during the final stages of cultivation in late spring, a condition typical of Mediterranean environments.

“It is important to conduct studies that show which wheat varieties are best adapted to different environmental growing conditions, especially in a context of climate change. Studying the past retrospectively can give us an idea of the evolution of wheat cultivation over the millennia since agriculture appeared in ancient Mesopotamia,” says Rut Sánchez-Bragado, first author of the study, who got a PhD at the UB.

“Awns are organs of the spike that have traditionally been associated with the plant’s adaptations to drought conditions,” says Josep Lluís Araus, professor at the Department of Evolutionary Biology, Ecology and Environmental Sciences of the Faculty of Biology.

“However, archaeological and historical records show that the wheat spike has existed predominantly with awns for more than ten millennia after the domestication of wheat. It is not until the last millennium that evidence shows in many cases the absence of awns, indicating a selection by farmers — probably in an undirected way — against this organ,” stresses Araus, one of the most cited authors in the world according to Clarivate Analytics’ Highly Cited Researchers (2022).

“The role of wheat awns in their performance remains controversial despite decades of studies,” says researcher Gustavo A. Slafer, corresponding author of the study.

Spike awns: beneficial for the plant?

Is the presence of awns on the spike beneficial for the plant and the crops? Although there is no scientific consensus, “everything suggests that in conditions where the plant does not suffer from water stress, the extra photosynthetic capacity of the awns does not compensate for other potential negative effects (reduced susceptibility to fungal diseases, limitation in the total number of large ones that an ear supports, etc.),” says Araus.

“However, in wetter climates the awns accumulate moisture and can promote the spread of diseases,” says Rut Sánchez-Bragado. “So, as the world’s population is continuously growing, it is necessary to investigate the role of the awned spikes in the changing conditions of our climate in order to meet the world’s demand for a primary food commodity such as wheat.”

In arid conditions, the spikes — including the awns — “have better physiological characteristics than the leaves. In addition, the awns allow the light captured by the crop to be more diffused, which facilitates a better distribution of light energy and allows the crop to photosynthesise more. Therefore, in arid conditions, the awns can still be beneficial for the crop, or at most, neutral,” concludes Professor Josep Lluís Araus.

Platform for building quantum networks

The two quantum systems were set up in in two laboratories, one in the building that houses the Department of Experimental Physics and one in the building that houses the Institute of Quantum Optics and Quantum Information of the Austrian Academy of Sciences. “Until now, trapped ions were only entangled with each other over a few meters in the same laboratory. Those results were also achieved using shared control systems and photons (light particles) with wavelengths that aren’t suitable for travelling over much longer distances,” Ben Lanyon explains. After years of research and development, the Innsbruck physicists have now managed to entangle two ions across campus. “To do this, we sent individual photons entangled with the ions over a 500-meter fiber optic cable and superimposed them on each other, swapping the entanglement to the two remote ions,” says Tracy Northup, describing the experiment. “Our results show that trapped ions are a promising platform for realizing future distributed networks of quantum computers, quantum sensors and atomic clocks.”

Ben Lanyon’s and Tracy Northup’s teams are part of the Quantum Internet Alliance, an international project under the European Union’s Quantum Flagship. The latest results have been published in Physical Review Letters. The research was financially supported by the Austrian Science Fund FWF and the European Union, among others.

These are among the results of a new study co-authored by University of Kansas professor of Communication Studies and friendship expert Jeffrey Hall.

“Quality Conversation Can Increase Daily Well-Being” was published in the journal Communication Research by Hall and co-authors Amanda Holmstrom, Natalie Pennington, Evan Perrault and Daniel Totzkay. The study was informed by and provides further support for Hall’s Communicate Bond Belong (CBB) theory of relationships. Hall is the director of KU’s Relationships and Technology Lab.

“This paper was an attempt to define quality communication in the context of relationships,” Hall said.”The types of communication we chose to study were ones shown in past research to make people feel more bonded through conversation.”

There were seven:

• Catching up
• Meaningful talk
• Joking around
• Showing care
• Listening
• Valuing others and their opinions
• Offering sincere compliments

Over 900 study participants from five university campuses — before, during and after pandemic lockdowns — were directed to engage in one of the seven communication behaviors on a single day, and then reported back that night about their feelings of stress, connection, anxiety, well-being, loneliness and the quality of their day.

As it turned out, Hall said, it didn’t matter which of these quality conversations someone had. The very act of intentionally reaching out to a friend in one of these ways was what mattered most.

“One of the take-home messages of this study is that there are many paths toward the same goal,” Hall said.

He said the study was also designed to explore the impact of both the quality and quantity of daily communications.

“There’s a lot of good research that says the number of interactions you have as well as the quality of interactions are both associated with being a less lonely, happier and more connected person,” said Hall. This study found that once is enough, but more is better. Participants who chose to have more quality conversations had better days.

“This means the more that you listened to your friends, the more that you showed care, the more that you took time to value others’ opinions, the better you felt at the end of the day,” he said.

“The experimental design means that it’s not just people who are already having fulfilling lives who have higher-quality conversations,” Hall said. “This study suggests that anyone who makes time for high-quality conversation can improve their well-being. We can change how we feel on any given day through communication. Just once is all it takes.”

The study also brought in Hall’s past research on different ways to connect in the era of social and mobile media. The study found high quality face-to-face communication was more closely associated with well-being than electronic or social media contact.

“If at least one of their quality conversations was face-to-face, that mattered,” Hall said.

The paper also explains why quality communication makes people feel better. CBB theory claims that people use conversations with friends to help get their need to belong met.

“Across these three studies, quality conversation mattered most for connection and stress,” Hall said. “This supports the idea that we use communication to get our need to belong met, and, in doing so, it helps us manage our stress.”

What is exciting about this research, Hall said, is that it shows there are a host of good things that come along with just one good conversation with a friend. This drives home the point that making time for quality conversation makes our days better.

Researchers found that the white dwarf is 56 percent the mass of our Sun. This agrees with earlier theoretical predictions of the white dwarf’s mass and corroborates current theories of how white dwarfs evolve as the end product of a typical star’s evolution. The unique observation yields insights into theories of the structure and composition of white dwarfs.

Until now, previous white dwarf mass measurements have been gleaned from observing white dwarfs in binary star systems. By watching the motion of two co-orbiting stars, straightforward Newtonian physics can be used to measure their masses. However, these measurements can be uncertain if the white dwarf’s companion star is in a long-period orbit of hundreds or thousands of years. Orbital motion can be measured by telescopes only over a brief slice of the dwarf’s orbital motion.

For this companion-less white dwarf, researchers had to employ a trick of nature, called gravitational microlensing. The light from a background star was slightly deflected by the gravitational warping of space by the foreground dwarf star. As the white dwarf passed in front of the background star, microlensing caused the star to appear temporarily offset from its actual position on the sky.

The results are reported in the Monthly Notices of the Royal Astronomical Society. The lead author is Peter McGill, formerly of the University of Cambridge (now based at the University of California, Santa Cruz).

McGill used Hubble to precisely measure how light from a distant star bent around the white dwarf, known as LAWD 37, causing the background star to temporarily change its apparent position in the sky.

Kailash Sahu of the Space Telescope Science Institute in Baltimore, Maryland, the principal Hubble investigator on this latest observation, first used microlensing in 2017 to measure the mass of another white dwarf, Stein 2051 B. But that dwarf is in a widely separated binary system. “Our latest observation provides a new benchmark because LAWD 37 is all by itself,” Sahu said.

The collapsed remains of a star that burned out 1 billion years ago, LAWD 37 has been extensively studied because it is only 15 light-years away in the constellation Musca. “Because this white dwarf is relatively close to us, we’ve got lots of data on it — we’ve got information about its spectrum of light, but the missing piece of the puzzle has been a measurement of its mass,” said McGill.

The team zeroed in on the white dwarf thanks to ESA’s Gaia space observatory, which makes extraordinarily precise measurements of nearly 2 billion star positions. Multiple Gaia observations can be used to track a star’s motion. Based on this data, astronomers were able to predict that LAWD 37 would briefly pass in front of a background star in November 2019.

Once this was known, Hubble was used to precisely measure over several years how the background star’s apparent position in the sky was temporarily deflected during the white dwarf’s passage.

“These events are rare, and the effects are tiny,” said McGill. “For instance, the size of our measured offset is like measuring the length of a car on the Moon as seen from Earth.”

Since the light from the background star was so faint, the main challenge for astronomers was extracting its image from the glare of the white dwarf, which is 400 times brighter than the background star. Only Hubble can make these kinds of high-contrast observations in visible light.

“The precision of LAWD 37’s mass measurement allows us to test the mass-radius relationship for white dwarfs,” said McGill. “This means testing the theory of degenerate matter (a gas so super-compressed under gravity it behaves more like solid matter) under the extreme conditions inside this dead star,” he added.

The researchers say their results open the door for future event predictions with Gaia data. In addition to Hubble, these alignments can now be detected with NASA’s James Webb Space Telescope. Because Webb works at infrared wavelengths, the blue glow of a foreground white dwarf looks dimmer in infrared light, and the background star looks brighter.

Based on Gaia’s predictive powers, Sahu is observing another white dwarf, LAWD 66, with NASA’s James Webb Space Telescope. The first observation was done in 2022. More observations will be taken as the deflection peaks in 2024 and then subsides.

“Gaia has really changed the game — it’s exciting to be able to use Gaia data to predict when events will happen, and then observe them happening,” said McGill. “We want to continue measuring the gravitational microlensing effect and obtain mass measurements for many more types of stars.”

In his 1915 theory of general relativity, Einstein predicted that when a massive compact object passes in front of a background star, the light from the star would bend around the foreground object due to the warping of space by its gravitational field.

Exactly a century before this latest Hubble observation, in 1919, two British-organized expeditions to the southern hemisphere first detected this lensing effect during a solar eclipse on May 19th. It was hailed as the first experimental proof of general relativity — that gravity warps space. However, Einstein was pessimistic that the effect could ever be detected for stars outside our solar system because of the precision involved. “Our measurement is 625 times smaller than the effect measured at the 1919 solar eclipse,” said McGill.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, D.C.

Decades of research has shown that we can transplant individual human and rodent neurons into rodent brains, and, more recently, it has been demonstrated that human brain organoids can integrate with developing rodent brains. However, whether these organoid grafts can functionally integrate with the visual system of injured adult brains has yet to be explored.

“We focused on not just transplanting individual cells, but actually transplanting tissue,” says senior author H. Isaac Chen, a physician and Assistant Professor of Neurosurgery at the University of Pennsylvania. “Brain organoids have architecture; they have structure that resembles the brain. We were able to look at individual neurons within this structure to gain a deeper understanding of the integration of transplanted organoids.”

The researchers cultivated human stem cell-derived neurons in the lab for around 80 days before grafting them into the brains of adult rats that had sustained injuries to their visual cortex. Within three months, the grafted organoids had integrated with their host’s brain: becoming vascularized, growing in size and number, sending out neuronal projections, and forming synapses with the host’s neurons.

The team made use of fluorescent-tagged viruses that hop along synapses, from neuron to neuron, to detect and trace physical connections between the organoid and brain cells of the host rat. “By injecting one of these viral tracers into the eye of the animal, we were able to trace the neuronal connections downstream from the retina,” says Chen. “The tracer got all the way to the organoid.”

Next, the researchers used electrode probes to measure the activity of individual neurons within the organoid when the animals were exposed to flashing lights and alternating white and black bars. “We saw that a good number of neurons within the organoid responded to specific orientations of light, which gives us evidence that these organoid neurons were able to not just integrate with the visual system, but they were able to adopt very specific functions of the visual cortex.”

The team was surprised by the degree to which the organoids were able to integrate within only three months. “We were not expecting to see this degree of functional integration so early,” says Chen. “There have been other studies looking at transplantation of individual cells that show that even 9 or 10 months after you transplant human neurons into a rodent, they’re still not completely mature.”

“Neural tissues have the potential to rebuild areas of the injured brain,” says Chen. “We haven’t worked everything out, but this is a very solid first step. Now, we want to understand how organoids could be used in other areas of the cortex, not just the visual cortex, and we want to understand the rules that guide how organoid neurons integrate with the brain so that we can better control that process and make it happen faster.”

Researchers at Baylor College of Medicine, the University of Michigan and collaborating institutions working with animal models of GVHD report today in the journal Immunity that alterations in the gut microbiome are connected to an increase in oxygen levels in the intestine that follows immune-mediated intestinal damage. Pharmacologically reducing intestinal oxygen levels alleviated the microbial imbalance and reduced the severity of the intestinal disease.

“There is a lot of data showing that microbes change in many diseases, but we do not understand how that happens,” said leading author Dr. Pavan Reddy, professor and director of Baylor’s Dan L Duncan Comprehensive Cancer Center, who was at the University of Michigan during the development of this project. “This study is one of the first to provide an explanation and a potential solution for the imbalance in the gut microbiome that exacerbates GVHD and possibly other inflammatory intestinal conditions.”

GVHD is a potentially life-threatening complication of bone marrow transplantation. “It is the complication that can prevent us from using this therapy that has proven to be effective to treat many blood cancers and inherited blood diseases,” Reddy said. “The idea is to understand what makes GVHD worse so we can effectively control it. The study also is relevant to more common inflammatory bowel diseases, including Crohn’s disease and ulcerative colitis.”

Reddy and his colleagues discovered that the damage immune cells cause to intestinal cells prevents these cells from fully using oxygen to conduct their normal functions. Consequently, all the oxygen that is not being used by intestinal cells oozes into the intestine, changing the environment for the resident microbes.

“Most of the ‘good microbes’ we have in the intestine grow in oxygen-poor environments — oxygen is toxic to them. They are called anaerobic (without oxygen) bacteria,” Reddy said. “When oxygen levels in the intestine increase, these microbes tend to disappear, and oxygen-loving microbes tend to grow. An increase in oxygen level provides an explanation for the microbiome changes in the context of these inflammatory diseases.”

The findings suggested that restoring the normal environment by reducing the oxygen level in the intestine could help reestablish the balance of the microbial community and lead to attenuation of GVHD.

“Indeed, we discovered that reducing the intestinal oxygen level actually made a difference in the progression of GVHD in the animal models,” Reddy said. “We found that a commonly used drug to reduce iron overload, an iron chelator, mitigated the microbial imbalance and reduced the severity of GVHD.”

Iron chelators have been used for many years to treat conditions in which excess iron causes tissue damage, such as hemochromatosis. Iron chelators are compounds that bind to iron, pulling it out and removing it from the body. “We discovered that iron chelators also can act as oxygen sinks,” Reddy said. “In our animal models, iron chelators removed iron from the intestine and that facilitated the restoration of an oxygen-poor environment that gave anaerobic bacteria an opportunity to bloom. Importantly, this reduced the severity of GVHD.”

The researchers’ next steps include conducting studies to determine whether iron chelation can help control the severity of GVHD in patients who have received a bone marrow transplant.

Another advantage of iron chelation would be that it may reduce or avoid the use of immune suppressor medications that are usually used to control GVHD. Suppressing the immune system may control GVHD, but also favors infections, which can be life-threatening. “If iron chelation helps control the condition in patients, it would be a novel non-immunosuppressive approach to treat GVHD with seemingly little side effects,” Reddy said.

Other contributors to this work include Keisuke Seike, Anders Kiledal, Hideaki Fujiwara, Israel Henig, Marina Burgos da Silva, Marcel R.M. van den Brink, Robert Hein, Matthew Hoostal, Chen Liu, Katherine Oravecz-Wilson, Emma Lauder, Lu Li, Yaping Sun, Thomas M. Schmidt, Yatrik M. Shah, Robert R. Jenq and Gregory Dick. The authors are affiliated with one or more of the following institutions: Baylor College of Medicine, University of Michigan, Okayama University Hospital, Rambam Health Care Campus-Israel, Memorial Sloan Kettering Cancer Center, Yale University School of Medicine and MD Anderson Cancer Center.

This work was supported by the US National Institutes of Health grants P01HL149633, HL152605, CA217156, R01CA148828, 4 R01CA245546 and R01DK095201. Further support was provided by National Cancer Institute award numbers R01-CA228358, R01-CA228308, P30 CA008748 MSK Cancer Center Support Grant/Core Grant and P01-CA023766; National Heart, Lung, Blood Institute award number R01-HL123340 and R01- 8 HL147584; Tri-Institutional Stem Cell Initiative and NIH grant CA46592.

“How the thalamus communicates with the cortex in a fundamental feature of how the brain interprets the world,” said Elly Nedivi, William R. and Linda R. Young Professor in The Picower Institute for Learning and Memory at MIT. Despite the importance of thalamic input to the cortex, neuroscientists have struggled to understand how it works so well given the relative paucity of observed connections, or “synapses,” between the two regions.

To help close this knowledge gap, Nedivi assembled a collaboration within and beyond MIT to apply several innovative methods. In a new study in Nature Neuroscience, the team reports that thalamic inputs into superficial layers of the cortex are not only rare, but also surprisingly weak, and quite diverse in their distribution patterns. Despite this, they are reliable and efficient representatives of information in the aggregate, and their diversity is what underlies these advantages.

Essentially, by meticulously mapping every thalamic synapse on 15 neurons in layer 2/3 of the visual cortex in mice and then modeling how that input affected each neuron’s processing of visual information, the team found that wide variations in the number and arrangement of thalamic synapses made them differentially sensitive to visual stimulus features. While individual neurons therefore couldn’t reliably interpret all aspects of the stimulus, a small population of them could together reliably and efficiently assemble the overall picture.

“It seems this heterogeneity is not a bug, it’s a feature that provides not only a cost benefit, but also confers flexibility and robustness to perturbation” said Nedivi, corresponding author of the study and a member of MIT’s faculty in the Departments of Biology and Brain and Cognitive Sciences.

Aygul Balcioglu, the research scientist in Nedivi’s lab who led the work, added that the research has created a way for neuroscientists to track all the many individual inputs a cell receives as that input is happening.

“Thousands of information inputs pour into a single brain cell. The brain cell then interprets all that information before it communicates its own response to the next brain cell,” Balcioglu said. “What is new and we feel exciting is we can now reliably describe the identity and the characteristics of those inputs, as different inputs and characteristics convey different information to a given brain cell. Our techniques give us the ability to describe in living animals where in the structure of the single cell what kind of information gets incorporated. This was not possible until now.”

‘MAP’ping and modeling

Nedivi and Balcioglu’s team chose layer 2/3 of the cortex because tthis layer is where there is relatively high flexibility or “plasticity,” even in the adult brain. Yet, thalamic innervation there has rarely been characterized. Moreover, Nedivi said, even though the model organism for the study was mice, those layers are the ones that have thickened the most over the course of evolution, and therefore play especially important roles in the human cortex.

Precisely mapping all the thalamic innervation onto entire neurons in living, perceiving mice is so daunting it’s never been done.

To get started the team used a technique established in Nedivi’s lab that enables observing whole cortical neurons under a two-photon microscope using three different color tags in the same cell simultaneously, except in this case, they used one of the colors to label thalamic inputs contacting the labeled cortical neurons. Whereever the color of those thalamic inputs overlapped with the color labeling excitatory synapses on the cortical neurons that revealed the location of putative thalamic inputs onto the cortical neurons.

Two-photon microscopes offer deep looks into living tissues, but their resolution is not sufficient to confirm that the overlapping labels are indeed synaptic contacts. To confirm their first indications of thalamic inputs, the team turned to a technique called MAP invented in The Picower Institute lab of MIT Chemical Engineering Associate Professor Kwanghun Chung. MAP physically enlarges tissue in the lab, effectively increasing the resolution of standard microscopes. Rebecca Gillani, a postdoc in the Nedivi lab, with help from Taeyun Ku, a Chung Lab postdoc, was able to combine the new labeling and MAP to definitely resolve, count, map, and even measure the size of all thalamic-cortical synapses onto entire neurons.

The analysis revealed that the thalamic inputs were rather small (typically presumed to also be weak and maybe temporary), and accounted for between 2 and 10 percent of the excitatory synapses on individual visual cortex neurons. The variance in thalamic synapse numbers was not just at a cellular level, but also across different “dendrite” branches of individual cells, accounting for anywhere between zero and nearly half the synapses on a given branch.

“Wisdom of the crowd”

These facts presented Nedivi’s team with a conundrum. If the thalamic inputs were weak, sparse and widely varying, not only across neurons but even across each neuron’s dendrites, then how good could they be for reliable information transfer?

To help solve the riddle, Nedivi turned to colleague Idan Segev, a professor at Hebrew University in Jerusalem specializing in computational neuroscience. Segev and his student Michael Doron used the Nedivi lab’s detailed anatomical measurements and physiological information from the Allen Brain Atlas to create a biophysically faithful model of the cortical neurons.

Segev’s model showed that when the cells were fed visual information (the simulated signals of watching a grating go past the eyes) their electrical responses varied based on how their thalamic input varied. Some cells perked up more than others in response to different aspects of the visual information, such ascontrast or shape, but no single cell revealed much about the overall picture. But with about 20 cells together, the whole visual input could be decoded from their combined activity — a so-called “wisdom of the crowd.”

Notably, Segev compared the performance of cells with the weak, sparse and varying input akin to what Nedivi’s lab measured, to the performance of a group of cells that all acted like the best single cell of the lot. Up to about 5,000 total synapses, the “best” cell group delivered more informative results but after that level, the small, weak and diverse group actually performed better. In the race to represent the total visual input with at least 90 percent accuracy, the small weak and diverse group reached that level with about 6,700 synapses while the “best” cell group needed more than 7,900.

“Thus heterogeneity imparts a cost reduction in terms of the number of synapses required for accurate readout of visual features,” the authors wrote.

Nedivi said the study raises tantalizing implications regarding how thalamic input into the cortex works. One, she said, is that given the small size of thalamic synapses they are likely to exhibit significant “plasticity.” Another is that the surprising benefit of diversity may be a general feature, not just a special case for visual input in layer 2/ 3. Further studies, however, are needed to know for sure.

In addition to Nedivi, Balcioglu, Gillani, Ku, Chung, Segev and Doron, other authors are Kendyll Burnell and Alev Erisir.

The National Eye Institute of the National Institutes of Health, the Office of Naval Research, and the JPB Foundation funded the study.

The researchers, from the University of Cambridge, along with colleagues from the US, Israel and Austria, developed a theory describing a new state of light, which has controllable quantum properties over a broad range of frequencies, up as high as X-ray frequencies. Their results are reported in the journal Nature Physics.

The world we observe around us can be described according to the laws of classical physics, but once we observe things at an atomic scale, the strange world of quantum physics takes over. Imagine a basketball: observing it with the naked eye, the basketball behaves according to the laws of classical physics. But the atoms that make up the basketball behave according to quantum physics instead.

“Light is no exception: from sunlight to radio waves, it can mostly be described using classical physics,” said lead author Dr Andrea Pizzi, who carried out the research while based at Cambridge’s Cavendish Laboratory. “But at the micro and nanoscale so-called quantum fluctuations start playing a role and classical physics cannot account for them.”

Pizzi, who is currently based at Harvard University, worked with Ido Kaminer’s group at the Technion-Israel Institute of Technology and colleagues at MIT and the University of Vienna to develop a theory that predicts a new way of controlling the quantum nature of light.

“Quantum fluctuations make quantum light harder to study, but also more interesting: if correctly engineered, quantum fluctuations can be a resource,” said Pizzi. “Controlling the state of quantum light could enable new techniques in microscopy and quantum computation.”

One of the main techniques for generating light uses strong lasers. When a strong enough laser is pointed at a collection of emitters, it can rip some electrons away from the emitters and energise them. Eventually, some of these electrons recombine with the emitters they were extracted from, and the excess energy they absorbed is released as light. This process turns the low-frequency input light into a high-frequency output radiation.

“The assumption has been that all these emitters are independent from one another, resulting in output light in which quantum fluctuations are pretty featureless,” said Pizzi. “We wanted to study a system where the emitters are not independent, but correlated: the state of one particle tells you something about the state of another. In this case, the output light starts behaving very differently, and its quantum fluctuations become highly structured, and potentially more useful.”

To solve this type of problem, known as a many body problem, the researchers used a combination of theoretical analysis and computer simulations, where the output light from a group of correlated emitters could be described using quantum physics.

The theory, whose development was led by Pizzi and Alexey Gorlach from the Technion, demonstrates that controllable quantum light can be generated by correlated emitters with a strong laser. The method generates high-energy output light, and could be used to engineer the quantum-optical structure of X-rays.

“We worked for months to get the equations cleaner and cleaner, until we got to the point where we could describe the connection between the output light and the input correlations with just one compact equation. As a physicist, I find this beautiful,” said Pizzi. “Looking forward, we would like to collaborate with experimentalists to provide a validation of our predictions. On the theory side of things, our work suggests many-body systems as a resource for generating quantum light, a concept that we want to investigate more broadly, beyond the setup considered in this work.”

The research was supported in part by the Royal Society. Andrea Pizzi is a Junior Research Fellow at Trinity College, Cambridge.