Author: Roheeni Saxena

If you glance at your desk or bedroom, you’ll probably immediately know if something is out of place, even if you’re not able to put your finger on what exactly is wrong without a closer inspection. That’s because humans have the ability to rapidly get the gist of a situation using only a quick glance.

A recent study published in PNAS shows that this ability goes way beyond day-to-day practicalities. Radiologists who specialize in the detection of breast cancer can discriminate between normal and abnormal mammograms in as little as half a second. But they may not even need to look at the cancerous tissue to do so.

The authors of the paper were interested in a phenomenon known as global processing, in which a quick glance at a large image gives insight into its meaning. They gave radiologists just a moment to glance at breast tissue images and compared the results of the radiologists’ insights to carefully analyzed images.

A new report published by the EOCD describes the world of 2050 sustaining 9.2 billion people. (credit: NASA/NOAA/GSFC/Suomi NPP/VIIRS/Norman Kuring)

If you look at a graph of our instrumental temperature records (like this one) you’ll see that temperatures seem to bounce around idly until after 1900, at which point a sustained rise becomes apparent. As a result, the pre-industrial temperature is typically pegged at the value it had in the late 1800s.

But a recent study published in Nature uses paleoclimate records from the 1500s to show that industrial-era warming first became apparent in the Northern Hemisphere in the mid-1800s. This paper suggests that humanity’s climate influence can be seen earlier than previously thought, so current models may underestimate the magnitude of human-caused climate change.

Paleoclimate data is reconstructed by combining observed climate data with known geochemical or biological markers of temperature. This information is analyzed using a statistical model that allows scientists to estimate temperatures for unobserved time points. For example, scientists can combine information from tree rings for years that have temperature readings to learn about how the temperatures affect tree growth. They can then use tree rings to make inferences about the climate in time periods before we started recording climate data, based on the changes that they see in the rings.

(credit: Walter Reed National Military Medical Center)

Recent advances in imaging have revealed that false memories can be held by the very same cells that hold accurate ones, but we don't have much information about how false memories get there in the first place. A recent study published in PNAS provides some insight into this issue, finding that false memories may arise from similarities among the items being remembered.

In neuroscience, false memories don’t necessarily refer to a sensational memory that might land you on a daytime talk show. Typically, neuroscientists are more interested in banal false memories. For example, a classic experiment in false memories involves showing a subject a series of words related to the winter season, like ice, snow, wind, etc. In this paradigm, even if subjects aren’t shown the word “cold,” they are still likely to remember having seen it. This is a classic false memory.

Neuroscientists have suspected that this type of false memory arises because the word “cold” is similar conceptually to the list of winter words that the subject did see. Even though the cognitive mechanism that causes this phenomenon (called conceptual similarity) is theoretically understood, however, its neural underpinnings have not been widely explored. Using a combination of the word-recall experiment described above and fMRI scans that could track the brain activity of the participants, the authors of this paper have begun to identify some of what’s behind the false memory effect.

In the US, carbon emissions connected with consumer purchases are twice as high as those related to home energy use and personal travel. Unfortunately, it’s challenging for consumers to get information about these emissions, even when they want to make environmentally friendly choices. A recent study in PNAS uses a series of tech interface experiments to assess whether carbon offset information will influence consumer behavior, finding that manufacturers can improve consumer satisfaction and reduce their environmental impact by providing consumers with environmentally friendly options.

These researchers were interested in techniques that make environmentally friendly choices easy for consumers to identify and whether those affect consumer choices. The choices were tested in the context of shipping options, ridesharing services, and online video streaming.

The first two experiments looked at Amazon Prime shipping. One of the benefits of Amazon Prime membership is free two-day shipping, so many consumers automatically select this even if they do not need their items within two days. To incentivize the selection of slower shipping, Amazon offers Prime customers a $1 credit if they select a no-rush shipping option instead.

(credit: http://www.colorado.feb.gov/index.php?content=17&page=Alternative%20Dispute%20Resolution)

Working collaboratively in small groups is one of the primary ways that modern humans accomplish anything. But what explains whether a group succeeds? Previous research on group dynamics has considered things like the demographic and psychological characteristics of individual group members. But a recent study published in PNAS indicates that their biology matters, too. Groups with collectively high testosterone and low cortisol (a stress hormone) show the highest performance in group tasks.

To examine the effects of hormones on group performance, the researchers collected saliva samples from 370 MBA students, then assigned them into groups of three to six members. The groups were then given a group decision-making task, and their performance was evaluated in light of the testosterone and cortisol levels in their saliva samples.

The decision-making task was a computerized exercise that asked the group to manage a fictional computerized laboratory for seven days, with the goal of maximizing profitability. The groups competed against each other to devise the most profitable management scheme. Since the lab required 24-hour monitoring and was too complicated for one person to manage on their own, the task required members to be interdependent and rely on each other to maximize their performance. However, team members were allowed to use any decision-making process they preferred to complete the task.

Major depressive disorder is a significant health problem, but its biological underpinnings aren't well understood. That's in part because there’s variability in both the disease's symptoms and its heritability. A recent study published in Nature Genetics identified five independent gene variants from four genome regions that are associated with depression, raising hopes that we can get a better handle on the disorder.

The study used a meta analysis of data collected by consumer genetics company 23andMe as well as previously published studies of depression. These studies can identify regions of the chromosome—and sometimes individual genes—that are frequently inherited along with the disorder. A correlation can imply causation.

The most significantly associated gene was OFLM4, which encodes for olfactomedin-4, a protein that promotes tumor growth and cell adhesion. This gene has not been previously associated with any psychiatric disorders, but it is known to be expressed in some brain regions, including the amygdala and the temporal lobe.

A cartoon representing neurotransmitters crossing a synapse. (credit: University of Connecticut)

Neurons communicate by sending chemical signals called neurotransmitters across synapses, specialized connections between two individual cells. This communication requires a delicate and intricate molecular architecture. A recent paper published in Nature has now shown that the structure of this intercellular space is more complicated than previously thought, and it probably helps boost the efficiency of the signaling.

The authors of this paper imaged three proteins found in the cell that start the signaling process. (Generically called presynaptic proteins, the ones looked at here are RIM1, RIM2, Munc13, and bassoon.) Each of these proteins was specifically tagged, and the authors plotted the density of their distribution across the active zones of the synapse.

The team then developed an algorithm that allowed it to identify small clusters of proteins based on their local density. These nanoclusters were more likely to be located near the center of each synapse than near the synaptic edges. This wasn’t true of all the proteins, but at least two were tightly restricted and a third less so (bassoon was almost uniform throughout the synapse).

Spread it with fire (credit: USDA)

Tuberculosis (TB), a bacterial infection, is currently the most deadly single pathogen in the world. How did this bacterium become a global scourge? A recent paper published in PNAS posits that when early humans began to utilize fires, they generated conditions ideal for the emergence of TB. If this hypothesis is correct, it could have serious implications for the study of emergent infectious diseases and how they interact with cultural and technological advances.

Evolutionary data, including whole genome sequencing, suggests that TB first became a human pathogen tens of thousands of years ago during the Neolithic period on the continent of Africa. It’s thought to have come from land mammals (especially bovines). There is also data suggesting that, in the Americas, TB hopped into infected humans from sea mammals. For the purposes of this paper, however, the authors chose to focus on the Africa-based ancestors of modern TB.

For an environmental pathogen to become an endemic human disease, it must first undergo a series of profound evolutionary transformations. The pathogen must adapt to the biological environment of their human hosts and must be able to readily move among them. The authors of the new paper discuss ways in which fire may have promoted these necessary transformations.

(credit: By Petr Pakandl - Own work, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=1176962)

In southern Italy, a plant pathogen called Xylella fastidiosa has been ushering in an agricultural, environmental, and political crisis. The infection is affecting olive trees, which are a critical part of Italian culture and heritage. Containment of this epidemic would require cutting down trees to prevent the spread of the disease. But that recommendation has been met with resistance by the locals, who have produced various conspiracy theories to explain why people are trying to get rid of their trees.

If this crisis is not resolved soon, the infection could spread throughout the region and cause serious plant losses in Europe and the Mediterranean, according to a new perspective in Science Magazine.

X. fastidiosa is a bacterial species that feeds on the xylem of plants and is spread by insects. In the past, the most severe economic effects of the X. fastidiosa were felt in the US and Brazil. These countries now have control plans that are deployed to reduce the spread of this disease, including reducing the insect population that spreads the disease and removing infected plants from areas with outbreaks. Currently, France has implemented similar procedures in response to the presence of the disease in Italy, but no such actions have been taken in southern Italy.

Bicycle racers—even those on different teams—often cooperate to allow the entire group to go faster. (credit: Flickr user Hans905)

Human cooperation is thought to have evolved because it benefits everyone involved. But we also know that cooperation doesn’t always make sense when subjected to a cost-benefit analysis. For example, people will often do favors for others when there is no expectation of a personal reward—or without even bothering to think about whether there might be a reward.

A recent study published in PNAS presents evidence that humans may engage in these types of uncalculating cooperative activities because it helps their reputation. By cooperating in the moment, people signal to others that they can be trusted to cooperate in the future.

The authors of the paper used a two-stage incentivized economic game to study this phenomenon. The first stage of the game asked participants to decide if they wanted to pay to benefit another player. Players could decide to help without looking at the cost, which was considered to be an uncalculating behavior, or they could check the cost before deciding to assist, which was interpreted as a calculating behavior. This calculating behavior was thought to be analogous to the type of cost-benefit analysis people often do before deciding to be cooperative.