Science

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Researchers at University of California have demonstrated the ability to create memories, erase them and create them again. The researchers used light-sensitive proteins and optical fibers to enact long-term potentiation between neurons, creating new associations.

“We could do it over and over, once we knew how to do it,” University of California lead researcher Roberto Malinow told The Speaker. 

In the study, researchers prepared the rats by injecting their brains with a virus that had been modified by a gene that produces a light-sensitive protein. The gene, once translated into protein, could be activated by a pulse of blue light delivered by an optical fiber the researchers had implanted in the rats’ brains.

Researchers fired a beam of light to the neurons that connect the sound processing region of the brain with a fear-related region, and then shocked the rats with electricity. The action created a memory of fear of sound.

“We can make a memory of something that the animal never experienced before,” Malinow said of the procedure.

The experiment was based on classic conditioning, wherein a tone is played to an animal followed by an electric shock. The animals develop a fear reaction to the tone.

The researchers then sought to erase the fear of sound they had created. They exposed the rats to a sequence of light pulses, which enacted long-term depression between the effected neurons. The rats no longer showed fear when a tone was simulated in the brain.

Fear could be created and erased over and over again, the researchers found. “We were playing with memory like a yo-yo,” stated Malinow.

Although in the study the researchers focused specific instance of memory, Malinow told us that the research had broader, though limited applications. “In our case, we focussed on a very specific memory–one we created artificially. In theory, one could do it to any memory.” However, Malinow told us, in practice it would be very difficult.

Regarding other types of memories, Malinow elaborated, “We don’t know which synapses are modified for any specific natural memory. Even if we did, it would be very difficult to control selectively the activity of just those synapses.”

The method used in the study, long-term potentiation (LPT), was discovered during research experiments in the 1960s and 70s when repeated bursts of electricity to a neuron in the hippocampus seemed to increase the cell’s ability to communicate with a neighboring neuron. Scientists have long theorized that LPT is the basis of memory.

The research has significance in the areas of health, particularly in the treatment of Alzheimer’s. Malinow mentioned several questions the team sought to answer with their research.

“Scientifically, we can use this methodology to probe many unanswered questions about memory,” Malinow said. “Does the material that builds up in Alzheimer’s disease actively remove memories? Can this be prevented? How can we inactivate (unwanted) memories? Is there a combination of drugs and behavioral protocols that could inactivate memories? What is the relation between protocol details and duration of memory?”

The University of California team is currently pursuing some of these issues.

By James Haleavy

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Tel-Aviv University researchers have found that agreeing with people on controversial issues causes them to reconsider their opinions, becoming more accepting of differing points of view.

The study, “Paradoxical thinking as a new avenue of intervention to promote peace,” was completed by Boaz Hameiria, Roni Poratc, Daniel Bar-Tald, Atara Bielerb, and Eran Halperinb, and was published in Proceedings of the National Academy of Sciences this month.

The researchers subjected study participants to videos of extreme versions of their beliefs–“consistent, though extreme, information” in the words of the researchers–and found that the participants sometimes came to view their opinions as irrational or absurd.

One hundred and fifty Israelis were repeatedly exposed to video clips that related to Palestinians, from the perspective of an extremist Israeli set of values. A control group watched neutral TV commercials.

The videos illustrated how the conflict with Palestine was consistent with many Israeli beliefs.

“For example, the fact that they are the most moral society in the world is one of the most basic beliefs of Israeli society,” said Eran Halperin, a psychologist at the Interdisciplinary Center Herzliya in Israel and one of the authors of the study. So when the researchers showed participants a video that claimed Israel should continue the conflict so that its citizens could continue to feel moral, people reacted angrily.

“You take people’s most basic beliefs and turn them into something that is absurd. For an outsider, it can sound like a joke, but for them, you are playing with their most fundamental belief.”

After being shown videos over a months-long period, participants were found to exhibit a 30 percent increase in willingness to re-evaluate their opinions on the responsibility for the conflict. The effects persisted one year after the study concluded. The study participants also reported voting more often for moderate parties, suggesting changed behavior in addition to changed opinions.

The researchers noted, however, that some study participants were effected in the opposite way, taking the videos at face value and assimilating the extreme messages into their opinions.

The significance of this work, according to the researchers, lies in a premise of most interventions that aim to promote peacemaking–that information that is inconsistent with held beliefs causes tension, which may motivate alternative information seeking.

The researchers said that they supposed facts were not at the heart of disagreements. “We truly believe that in most intractable conflicts, the real problems are not the real issues,” Halperin said. Although both sides of a conflict may know how to find resolution, “psychological barriers… prevent societies from identifying opportunities for peace.”

By James Haleavy

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A recent study by Pennsylvania State and the University of Texas has looked at the varying levels of generosity exhibited by people around the world, and has found that, although some countries are much more generous than others, the issue is more complex than some might think.

The report, “Accepting Inequality Deters Responsibility: How Power Distance Decreases Charitable Behavior,” was completed by Pennsylvania State Smeal College of Business’ Karen Winterich, assistant professor of marketing, and Yinlong Zhang of the University of Texas-San Antonio, and will be published in the Journal of Consumer Research’s August edition.

“Our research examines whether cultural values can explain the different levels of charitable giving between different countries,” the authors stated. “Could power distance, which is the extent that inequality is expected and accepted, explain why some countries and consumers are more likely to engage in prosocial behavior, including donations of both money and time?”

The researchers looked at prosocial behaviors such as giving money, volunteering time and helping strangers, and found that some countries are much more generous than others. Across the world, 28 percent of people donate money, but in China, Greece and Russia, for example, only 10 percent or less do. In Australia, Ireland and Canada, over 60 percent donate money. Ten percent of Indians, Bulgarians and Singaporeans volunteer their time, while over 40 percent of Canadians, Americans and Liberians do.

The researcher found, however, that one notable factor had a marked influence on generosity in the least generous nations. The less generous nations were willing to aid victims of natural disasters and other circumstances deemed out of the personal control of the needy, but were not willing to help those people they considered to be “at fault” for their situation, such as the obese and sedentary.

The most generous nations were more willing to help all because, the researchers said, culturally they were less accepting or expectant of inequality in wealth and power.

“In a high power distance society, inequality is seen as the basis of societal order,” wrote the authors. “Uncontrollable need increases feelings of responsibility to offer aid among those who otherwise would not feel responsible to offer aid for a need that is controllable and may simply be part of the accepted inequality in society.”

By Day Blakely Donaldson

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A new joint collaboration between Tel Aviv University, Columbia University’s Medical Center, and the Cold Spring Harbor Laboratory (CSHL) has demonstrated that life events can effect the genetic heritage of an organism’s immediate descendants. The Columbia team was able to show that transgenerational memory is passed on through an organism’s short RNAs for at least three generations.

“It shows that our experiences shape our inheritance… and that’s there’s a memory of our ancestors’ lives,” Tel Aviv’s Oded Rechavi, lead researcher on the project, told The Speaker.

The study, “Starvation-Induced Transgenerational Inheritance of Small RNAs in C. elegans,” was completed by Leah Houri-Ze’evi, Sarit Anava, Wee Siong Sho Goh, Sze Yen Kerk, Gregory J. Hannon and Oliver Hobert, in addition to Rechavi. The study was supported by the Howard Hughes Medical institute and was published in the June 10 edition of Cell.

In its research, the team demonstrated that drastic environmental changes, such as famine, can cause genetic changes that are passed down through at least three consecutive generations.

The team demonstrated this using roundworms. The team starved roundworms for six days and examined their cells. The starved roundworms were found to have developed a specific set of small RNAs.

Small RNAs are a type of non-coding RNA (ncRNA), functional RNA molecules that are not translated into protein (as are DNA). Many ncRNAs have been newly identified in recent years, and have not yet been validated for their function. Small RNAs are involved in various aspects of genetic expression.

“Small RNA-induced gene silencing can persist over several generations via transgenerationally inherited small RNA molecules in C. elegans,” stated Rachavi. Starvation induced changes in the roundworms’ small RNA were inherited by subsequent generations. The genetic inheritance took place apparently independent of DNA involvement.

Based on evidence of human famines and animal studies, it had long been suspected that starvation can affect the health of descendants, but the means by which such genetic inheritance was conveyed was not known.

“[E]vents like the Dutch famine of World War II have compelled scientists to take a fresh look at acquired inheritance,” said Oliver Hobert, PhD, professor of biochemistry and molecular biophysics and Howard Hughes Medical Institute Investigator. Animal studies have been conducted showing that, like humans who give birth during famine, animals such as rats can be caused to produce thin or obese offspring.

Roundworms were used in another small RNA-related study in 2011, when they were used to show that virus immunity developed during a parent’s life could be passed on to offspring for many generations through small RNA viral-silencing.

Hobert suspected that the small RNAs were somehow finding their way into the worms’ sperm and egg cells. “When the worms reproduced, the small RNAs could have been transmitted from one generation to the next in the cell body of the germ cells, independent of the DNA.”

How small RNAs were entering germ cells, and what types of biological experiences were registered by small RNA changes, Rechavi told The Speaker, “is a completely uncharted area.”

Rechavi said that the response to an organism’s environment was, however, “not necessarily only dietary related. In theory… any response that would produce a strong systemic small RNA response could be heritable. It’s not clear exactly how small RNAs find their way to the germline, but in worms several genes that enable cell-to-cell transfer of small RNAs have been discovered.”

In Rechavi’s previous work he has demonstrated that human immune cells, such as T or NK cells, can exchange small RNAs with other cells, and that some small RNAs can be found circulating in human blood.

“In general, I would suspect that it would be worth ‘memorizing,’ or producing a heritable response,” Rechavi told us, “cues which are really important for the survival of the organism.”

The implications of the study include that the biology of inheritance is more complicated than previously thought.

“[They] suggest that we should be aware of other things—beyond pure DNA changes—that may have a long-term impact on the health of an organism,” said Dr. Hobert. “In other words, something that happened to one generation, whether famine or some other traumatic event, may be relevant to the health of its descendants for generations.”

The study has also been said to give weight to the long-dismissed Lamarckian theory of genetics, which proposed that organisms adapt to their environment and pass on adaptations to offspring. Lamarckian genetics has traditionally been contrasted with Darwinian genetics, which theorized that all mutations were random, and the randomly mutated offspring were selected by nature according to their success surviving and reproducing.

Next for Rechavi and his team is to further pursue an understanding of the effects of environment on genetics. “We are testing how stable these effects are,” Dr. Rechavi told us. “exactly how the small RNAs are produced, and which regulated genes are most important in the process. We are also interested in examining the generality of this mechanism. This could be an important mechanism that acts side by side along with the traditional DNA-based inheritance mechanism.”

By Day Blakely Donaldson

Researchers testing the amount of plastic garbage polluting the earth’s oceans have discovered a mystery. Instead of finding evidence of the millions of tons of durable plastic garbage expected to litter the ocean surface, they found only tens of thousands.

In the 1970s, the National Academy of Sciences estimated that 45,000 tons of plastic garbage reached the world’s oceans every year. Today the world produces five times as much plastic as it produced in the 70s, so researches expected to find evidence of millions of tons of plastic garbage in the oceans. They were surprised that after looking at over 3,000 samples, they found only 7,000 – 35,000 tons of plastic garbage.

The research was conducted by ecologists at the University of Cadiz in Spain. The report, “Plastic debris in the open ocean,” was completed by Andrés Cózara, Fidel Echevarríaa, Ignacio González-Gordilloa, Xabier Irigoienb, Bárbara Úbedaa, Santiago Hernández-Leónd, Álvaro T. Palmae, Sandra Navarrof, Juan García-de-Lomasa, Andrea Ruizg, María L. Fernández-de-Puellesh, and Carlos M. Duartei, and was published by the National Academy of Sciences.

The researchers do not know where the missing garbage has gone. The researchers did find clues, however. A primary piece of evidence was that far fewer plastic fragments under 5 millimeters were found than larger fragments.

The researchers guessed that somehow the smallest pieces of plastic were finding their way to deeper waters.

Another guess was that mesopelagic fish, which inhabit the oceans at 660-3,300 feet below the surface, were feeding on the plastic fragments when they came to the surface at night. The researchers pointed out that the normal food of these fish is roughly the same size–zooplankton. When the fish excrete the debris, it may sink deeper, or the debris may be carried deeper when the fish die.

Another finding was that bacteria was growing on the plastic fragments. The bacteria’s weight may be pushing the fragments down, the researchers suggested.

These guesses were phrased by the researcher this way: “Our observations of the size distribution of floating plastic debris point at important size-selective sinks removing millimeter-sized fragments of floating plastic on a large scale. This sink may involve a combination of fast nano-fragmentation of the microplastic into particles of microns or smaller, their transference to the ocean interior by food webs and ballasting processes, and processes yet to be discovered.”

The surprising finding led the researchers to conclude a further question was pending. “Resolving the fate of the missing plastic debris is of fundamental importance to determine the nature and significance of the impacts of plastic pollution in the ocean,” the researchers stated.

By Sid Douglas

PNAS

Global Ocean Commission

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Two marine researchers have published a report on two prominent near-bottom fish species of the northern seas, looking at how the two species fared in the warming waters of the past decade. The researchers looked at Bering Sea walleye pollock and Atlantic cod, and proposed that the differences in how the two species fared may be indicative of how other species will variously thrive or suffer during global warming.

The northern waters of both the cod and the pollock have warmed over the past decade, but one of the species appears to have prospered, while the other has diminished. “These response patterns appear to be linked to a complex suite of climatic and oceanic processes that may portend future responses to warming ocean conditions,” stated the researchers.

The report, “Distinct impact of tropical SSTs on summer North Pacific high and western North Pacific subtropical high,” was written by Anne B. Hollowed of the Alaska Fisheries Center’s National Marine Fisheries Service and Svein Sundby of the Institute of Marine Research, and was published in Science Magazine.

The report explained that Atlantic cod stock biomass has steadily increased since the 1980s, paralleling an increase in northern oceanic tempertures. Atlantic Cod, which spawn in the southern end of their territory, are thought to require warm temperatures to produce strong year classes. “During warming phases,” the report read, “the spawning stock biomass gradually builds up and the cod spawn rather north,” whereas in cooler phases spawning takes place further south. A similar trend of increasing fish stocks accompanied the warming period between the 1920s and the 1940s. The recent success of Atlantic cod stocks is thought to be the result of warmer weather, in addition to the effects of fishing limitations.

On the other hand, Bering Sea pollock–the largest fish stock in the northeast Pacific Ocean–declined in the early 2000. The stock began rising again before 2010, but did not reach pre-2000 levels.

The habitat and diet of pollock is thought to account for the difference. Bering Sea pollock feed throughout the middle and outer shelf regions and generally avoid bottom waters below 0 degrees Celsius–and so are usually found in the southern Bering Sea. The fish expand across the shelf in warmer years. The pollock stock is made up of several age groups, each of which has been affected by prey availability and the ability to accumulate winter stores of energy.

The pollock are thought to be affected by temperature most significantly in the first year of their life–due to the effects of temperature on their first summer.

The report concluded, “The response of seafloor fish species in the border regions between the boreal and Arctic domains to climate variability may provide clues to how future antrhopogenic climate change will influence fish stocks and marine ecosystems at high latitudes.”

The report also made more specific predictions about the future of Atlantic cod and Bering Sea pollock. The cod, which have already reached the shelf break and the deep polar basin, can advance no further north, and so may now advance eastward along the Siberian shelf as new habitats open up due to the loss of sea ice at the Siberian shelf and the Northeast Passage. The pollock face an uncertain future, because the suite of interacting processes that govern their health is more complex, and because sea ice is expected to continue to form in fall and winter, leaving a cold remnant in summer, making the cold pools inhospitable to the fish.

by Sid Douglas

Nature

Neuroscientists and engineers at North Carolina’s Duke University have pioneered a method with which the effects of transcranial magnetic stimulation (TMS) on the brain can be measured. The Duke team has made it possible to measure the response of a single neuron to an electromagnetic charge–something that has not before been possible. The work offers the potential to improve and initiate novel TMS therapy approaches.

“This report focused on the innovative methodology that allowed us to record from single neurons,” Duke professor of biomedical engineering, electrical and computer engineering, and neurobiology and lead researcher on the team, Warren Grill, told The Speaker. The team was able to record an increase in a neuron’s firing rate in the wake of the short, rapidly varying magnetic field created by TMS. The increase in firing lasted approximately 100 ms after the TMS pulse, according to Grill.

The report, “Simultaneous transcranial magnetic stimulation and single-neuron recording in alert non-human primates,” was authored by Jerel K Mueller, Erinn M Grigsby, Vincent Prevosto, Frank W Petraglia III, Hrishikesh Rao, Zhi-De Deng, Angel V Peterchev, Marc A Sommer, Tobias Egner, Michael L Platt, in addition to Grill, was published in Nature and was supported by a Duke Institute for Brain Sciences Research Incubator Award and by a grant from the National Institute of Neurological Disorders and Stroke of the National Institutes of Health.

Transcranial magnetic stimulation is a widely-used procedure wherein electromagnetic coils are held up to the skull and short electromagnetic pulses are run through the coil. It has long been understood that neurons react to TMS, and the procedure has been used to treat psychiatric disorders, substance abuse and other health conditions. Although preferable to other treatment methods because TMS is noninvasive, its mechanisms have always been poorly understood, making improvements difficult.

In part, the barrier to understanding the mechanisms of TMS is due to the difficulty of measuring neural responses during the procedure. The neural response is electric,and the current charging the TMS bears an overwhelmingly stronger electric charge.

Grill said of the difficulty in understanding TMS without measuring its effects, “Nobody really knows what TMS is doing inside the brain, and given that lack of information, it has been very hard to interpret the outcomes of studies or to make therapies more effective. We set out to try to understand what’s happening inside that black box by recording activity from single neurons during the delivery of TMS in a non-human primate. Conceptually, it was a very simple goal. But technically, it turned out to be very challenging.”

Although thousands of times smaller than the charge of the TMS, the neural response can be measured by the research team’s hardware. The team also overcame the obstruction posed by the recording device, which also emitted an electric current.

“Studies with TMS have all been empirical,” said Grill. “You could look at the effects and change the coil, frequency, duration or many other variables. Now we can begin to understand the physiological effects of TMS and carefully craft protocols rather than relying on trial and error. I think that is where the real power of this research is going to come from.”

The Duke team’s research is open to anyone with a lab, according to the researchers. “[A]ny modern lab working with non-human primates and electrophysiology can use this same approach in their studies,” said Grill. The team said they hope others would pursue this line of research, and contribute to improvements in TMS therapy.

“This research will allow us first to quantify and understand the effects of TMS on neurons, and subsequently to design novel approaches, including stimulation waveforms and stimulation coil design to amplify or modify those effects,” Grill told us.

By Day Blakely Donaldson

Nature