Tag: Neuroscience

How Do Bats Get Street-Smart?

TAU researchers find that baby fruit bats acquire their boldness from their adoptive mothers.

Tel Aviv University researchers conducted the first ever “cross-adoption” behavioral study in bats, whereby pups of urban fruit bats were adopted by rural mothers and vice versa in order to learn whether the relative boldness of city bats is a genetic or acquired trait. Prof. Yovel: “We wanted to find out whether boldness is transferred genetically or learned somehow from the mother. Our findings suggest that this trait is passed on to pups by the mothers that nurse and raise them, even when they are not their biological mothers.” Thus, the bat species’ willingness to take risks is an acquired rather than hereditary trait, passed on in some way from mother to young pup

The study was led by TAU’s Prof. Yossi Yovel, Head of the Sagol School of Neuroscience, member of the School of Zoology at The George S. Wise Faculty of Life Sciences and The Steinhardt Museum of Natural History, and recipient this year of the Blavatnik Young Scientists Award in Israel and the Kadar Family Award for Outstanding Research at TAU. It was conducted by Dr. Lee Harten, Nesim Gonceer, Michal Handel and Orit Dash from Prof. Yovel’s laboratory, in collaboration with Prof. H. Bobby Fokidis from Rollins College in Florida. The paper was published in BMC Biology.

Rural Bats More Risk Adverse

Dr. Harten explains: “While most animals do not live in an urban environment, some species thrive in it. We are trying to understand how they do this. Fruit bats are an excellent example of a species that has adapted well to the human environment of the city. Bat colonies thrive in Tel Aviv and other cities, while other colonies still live in rural areas. Research has shown that city-adapted fruit-bats tend to be bolder and take more risks than those living in the wild. We wanted to examine, under laboratory conditions, whether this trait is genetic or acquired.

In a preliminary experiment the researchers placed food inside a box that required adult bats to land and enter in order to get the food. They found that urban bats solved the problem immediately, while rural bats hesitated and took several hours to learn the trick. Prof. Yovel: “Similar results were observed in past experiments with birds: birds living in the city take more risks than birds of the same species residing in rural areas. Our study was the first to test this issue in bats.”

Bat Boldness: Genetic or Acquired?

The next step was testing whether this boldness is a hereditary trait, or a quality acquired by experience. To this end, the researchers conducted the same experiment with young bat pups, still fed by their mothers, who had never searched for food independently. They found that the urban pups, just like their parents, are bolder and learn faster than their rural counterparts.

Prof. Yovel: “These findings first led us to think that boldness is hereditary – passed on genetically from the urban parents to their pups. However, we know that young pups are still exposed to their mothers after birth. We decided to check whether pups learn from their mothers or are influenced by them in some other way.”

To answer this question, the researchers introduced a cross-adoption method: pups born to urban mothers were raised by rural mothers, and vice versa. They note that this was the first experiment of this type ever conducted in bats, and also the first ‘nature vs. nurture’ study for boldness in urban animals.

Liquid Courage?

Dr. Harten: “We found that the pups behaved like their adoptive mothers, not like their biological mothers. This means that boldness is an acquired rather than hereditary trait, passed on in some way from mother to young pup. We hypothesize that the agent may be some substance in the mother’s milk.” In an additional experiment the researchers discovered that the urban mothers’ milk contains a higher level of the hormone cortisol than the milk of rural mothers. It has not yet been ascertained, however, that this is the agent for the inter-generational transfer of boldness.

Prof. Yovel concludes: “The urban environment presents animals with more challenges and a greater variety of situations. It is therefore plausible that bats and other animals living in the city require more boldness and higher learning skills. In our study we focused on bat pups, examining whether bold behavior is the result of genetics, environment, or some combination between the two. In light of our findings, we hypothesize that the trait is passed on to pups in early stages of development, through some component of their mothers’ milk.” Dr. Harten adds: “We believe that a better understanding of the needs and behaviors of urban animals can help us protect them and adapt urban development to their needs.” 

Featured image: “Baby bat with its adoptive mother (Photo: Yuval Barkai)”

Can’t Multitask Anymore?

Non-invasive brain stimulation may boost mobility in the elderly and prevent falls.

Walking while simultaneously carrying out a cognitive task, like talking on a cellphone or with a companion, happens frequently throughout the day for many of us. The concurrent performance of two tasks requires the ability to split attention. For older people, difficulties performing another task while walking or standing reflect an existing and/or a potential problem concerning both functions. It also means an increased risk of falling, which can have many severe and undesirable consequences for older adults.

Tel Aviv University researchers sought to examine the benefits of very low intensity, non-invasive electrical stimulation of various parts of the brain, on the capability of older adults to walk or stand while simultaneously carrying out a cognitive task, a common dual-task situation that can determine their overall functionality. They hoped that this might improve their ability to perform both tasks simultaneously in a safer manner. The researchers found that when stimulating the dorsal lateral pre-frontal cortex (DLPFC), a cognitive brain area responsible for dividing attention and executive functions, the immediate, negative impact of a dual-task on standing and walking performance was significantly reduced.

The study team under the leadership of Prof. Jeffrey Hausdorff of the Sackler Faculty of Medicine, the Sagol School of Neuroscience, and the Tel Aviv Sourasky Medical Center (Ichilov), and Dr. Brad Manor at Harvard Medical School, as well as researchers from Harvard University, research and medical institutions in the US and Spain, and the Tel Aviv Sourasky Medical Center (Ichilov). The study was published in the Annals of Neurology, the journal of the American Neurological Association. The research was funded by a grant from the US-Israel Binational Science Foundation.

Gentle Power

The study cohort included 57 subjects over the age of 70. Each of them was tested by 4 different treatments:

  • Sham, designed not to have any influence at all, but to rule out any placebo effects;
  • Stimulation of a cognitive area of the brain (DLPFC) that is responsible for dividing attention;
  • Stimulation of a sensory-motor area of the brain which contributes to the regulation of walking;
  • Simultaneous stimulation of both areas – motor and cognitive – together. 

Each treatment included non-invasive stimulation using a very low-intensity electric current for 20 minutes. Immediately upon the conclusion of the treatment, the walking and standing sway of each subject were evaluated, with and without the request to also perform a cognitive task.

The study showed that stimulation of the cognitive area, whether alone or together with the stimulation of the motor area, reduced the negative effects of the cognitive task on walking and standing stability by about 50%.  Stimulation of the sensory-motor area alone and sham stimulation did not improve the subjects’ performance. The researchers explain that, since the stimulation is gentle, it does not activate brain neurons but only increases their excitability; in other words, it facilitates the ability of the patient to activate those neurons in his or her brain.

“In our study, we demonstrated that a low-level, gentle stimulation of a specific cognitive area of the brain can improve the performance of older adults when they carry out the double task of walking or standing in place while at the same time performing a cognitive task, at least within the immediate time range,” says Prof. Hausdorff.  

“We hope that a series of treatments will lead to similar positive results over a more protracted period: to improve standing stability and walking capability, diminish the risks of falling, and perhaps also enhance cognitive function among the elderly population. This treatment is safe, and we hope that, in time, people will be able to undergo self-treatment in their own homes. Additionally, we foresee the possibility of combining this type of therapy with exercise and other modes of intervention that can help to improve walking, to enhance thinking, and to reduce the risk of falls. There is evidence that combined therapy could prove to be the most effective solution, but further research is required to examine this,” he concludes.

Tel Aviv Bats Have More Fun

More adventurous than their rural counterparts, fruit bats in Tel Aviv enjoy what the city has to offer.

Urbanization processes tend to lead animals to leave the city, but some animals are able to thrive in an urban domain. A new Tel Aviv University study found that fruit bats, just like humans, are able to adapt to a variety of environments, including the city and the countryside.

Prof. Yossi Yovel: “How animals cope with urbanization is one of the most central and important questions in ecological research today. Understanding the ways in which animals adapt to urban areas can help us in our conservation efforts. The urban environment is characterized by much fragmentation, and we currently have little understanding of how animals, especially small animals, like the bats, move and fly in such areas.”

The City Bat and the Country Bat

The urban environment is fundamentally different from the rural environment in terms of the diversity and accessibility of food. Although the city has a larger variety of trees per area, there are many challenges that bats have to face, such as buildings and humans. In rural areas, on the other hand, most of the trees are concentrated in orchards without barriers, but have less diversity – the trees are mostly of one type.

Because of the environmental differences between the city and the country with regards to the distribution and variety of fruit trees, the nature of the bats’ movement when foraging in these areas differs as well. In this new study, the researchers compared the nature of the movement of rural bats and city bats as they foraged for food, using tiny GPS devices to track the bats to see if the way they moved while searching for food was affected by their living environment, or the environment in which they were foraging.

The study was led by research student Katya Egert-Berg, under the guidance of aforementioned Prof. Yossi Yovel, head of Tel Aviv University’s Sagol School of Neuroscience and a faculty member of the School of Zoology in The George S. Wise Faculty of Life Sciences and The Steinhardt Museum of Natural History, as well as a recipient of the 2021 Kadar Family Award for Outstanding Research. The study was published in the journal BMC Biology.

Enjoying their Meals in the Big City

The researchers found that the fruit bats hunting for food in the city are much more exploratory, enjoy the abundance of the urban environment, visit a variety of fruit trees every night, and feed from a wide a variety of trees. In contrast, the rural bats focus on only one or two fruit trees each night. Moreover, the researchers found that among the rural bats who rest in the countryside, there were many who left their rural homes every night in search of food in the city, and then flew back to the country after their meal. During their stay in the city, such bats share the same flight patterns as those of the bats that live in the city around the clock.

The study’s findings led the researchers to assess that even bats that live in rural environments their entire lives will be able to orient themselves in an urban, industrialized environment. They explain that there are animal species that are flexible – for them, the ability to adapt to a new and unfamiliar environment such as an urban settlement is an acquired skill. Such species, of which the fruit bats are an example, will in many cases be able to adapt to life in urban areas.

Featured image: A Tel Aviv bat in action. Photo: S. Greif

Bats ‘Social Distance’ Too

TAU researchers find that bats also self-isolate when sick, helping prevent outbreaks of epidemics.

The Covid-19 pandemic has introduced us to expressions such as ‘lockdown’, ‘isolation’ and ‘social distancing’, which became part of social conduct all over the world. And while bats have been widely assumed to be source of coronavirus, apparently they too maintain social distancing, which might help prevent the spread of contagious diseases. Researchers from Tel Aviv University demonstrate that sick bats, just like us humans when we are sick, prefer to stay away from their communities. This is probably a means for recovery and possibly also a measure for protecting others. The study was conducted by postdoctoral researcher Dr. Kelsey Moreno and PhD candidate Maya Weinberg at the laboratory of Prof. Yossi Yovel, Head of the Sagol School of Neuroscience and a researcher at the School of Zoology at the George S. wise Faculty of Life Sciences. The study has been published in Annals of the New York Academy of Science.

“If we protect them, they will also protect us”

The study monitored two colonies of Egyptian fruit bats – one living in an enclosure and the other in its natural environment. To examine the behavior of bats when they get sick, the researchers injected several bats in each group with a bacteria-like protein, thereby stimulating their immune response without generating any real danger to the bats. Tests revealed symptoms such as a high fever, fatigue and weight loss, and the ‘ill’ bats’ behavior was tracked with GPS. The researchers discovered that the ‘sick’ bats chose to keep away from the colony. In the first group, they left the bat cluster of their own accord and kept their distance. In the second group the ‘ill’ bats likewise moved away from the other bats in the colony, and also stayed in the colony and did not go out in search of food for two successive nights. Research student Maya Weinberg explains that this social distancing behavior is probably caused by the need to conserve energy – by avoiding the energy-consuming social interactions in the group. Weinberg emphasizes, however, that this behavior can also protect the group and prevent the pathogen from spreading within the colony. Moreover, the fact that sick bats don’t leave the cave, prevents the disease from spreading to other colonies. “The bats’ choice to stay away from the group is highly unusual for these animals. Normally these bats are extremely social creatures, living in caves in very crowded conditions,” says Weinberg. “In fact, the ‘sick’ bats’ behavior is very reminiscent of our own during recovery from an illness. Just as we prefer to stay home quietly under the blanket when we are ill, sick bats, living in very crowded caves, also seek solitude and peace as they recuperate.” Prof. Yovel adds that the study’s findings suggest that the likelihood of bats passing pathogens to humans under regular conditions is very low, because sick bats tend to isolate themselves and stay in the cave. “We observed that during illness bats choose to stay away from the colony and don’t leave the cave, and thus avoid mixing with other bats. This suggests that in order to encounter a sick bat, people must actually invade the bats’ natural environment or eliminate their habitats. In other words, if we protect them, they will also protect us.”

Time Flies and So Do Bats

Bats map the world in units of time, an innate ability.

Bats know the speed of sound from birth. Unlike humans, who map the world in units of distance, bats map the world in units of time. This means that the bat actually perceives an insect as being at a distance of nine milliseconds, and not one and a half meters, as previously thought. TAU researchers proved this, by raising bats from the time of their birth in a helium-enriched environment in which the speed of sound is higher than normal. The study was published in PNAS.

Born this way

In order to determine where things are in a space, bats use sonar – they produce sound waves that hit objects and are reflected back to the bat. Bats can estimate the position of the object based on the time that elapses between the moment the sound wave is produced and the moment it is returned to the bat. This calculation depends on the speed of sound, which can vary in different environmental conditions, such as air composition or temperature. For example, there could be a difference of almost 10% between the speed of sound at the height of the summer, when the air is hot and the sound waves spread faster, and the winter season. Since the discovery of sonar in bats 80 years ago, researchers have been trying to figure out whether bats acquire the ability to measure the speed of sound over the course of their lifetime or are born with this innate, constant sense. Now, researchers led by Prof. Yossi Yovel, head of the Sagol School of Neuroscience and a faculty member of the School of Zoology in The George S. Wise Faculty of Life Sciences and his former doctoral student Dr. Eran Amichai have succeeded in answering this question. The researchers conducted an experiment in which they were able to manipulate the speed of sound. They enriched the air composition with helium to increase the speed of sound, and under these conditions raised bat pups from the time of their birth, as well as adult bats. Neither the adult bats nor the bat pups were able to adjust to the new speed of sound and consistently landed in front of the target, indicating that they perceived the target as being closer – that is, they did not adjust their behavior to the higher speed of sound. Because this occurred both in the adult bats that had learned to fly in normal environmental conditions and in the pups that learned to fly in an environment with a higher-than-normal speed of sound, the researchers concluded that the rate of the speed of sound in bats is innate – they have a constant sense of it. “Because bats need to learn to fly within a short time of their birth,” explains Prof. Yovel, “we hypothesize that an evolutionary ‘choice’ was made to be born with this knowledge in order to save time during the sensitive development period.”

With Time as Their Compass

Another interesting conclusion of the study is that bats do not actually calculate the distance to the target according to the speed of sound. Because they do not adjust the speed of sound encoded in their brains, it seems that they also do not translate the time it takes for the sound waves to return into units of distance. Therefore, their spatial perception is actually based on measurements of time and not distance. Prof. Yossi Yovel says, “What most excited me about this study is that we were able to answer a very basic question – we found that in fact bats do not measure distance, but rather time, to orient themselves in space. This may sound like a semantic difference, but I think that it means that their spatial perception is fundamentally different than that of humans and other visual creatures, at least when they rely on sonar. It’s fascinating to see how diverse evolution is in the brain-computing strategies it produces.”

Fireflies’ Protective ‘Musical Armor’ Against Bats

Trailblazing TAU study reveals that fireflies produce strong ultrasonic sounds that may potentially work to deter bats.

They sure know how to put on a show at nights – fireflies are striking with their glow-in-the-dark feature. But have you ever stopped and wondered how these glowing insects defend themselves against predators? A trailblazing TAU study reveals that fireflies produce strong ultrasonic sounds that may potentially work to deter bats, serving as a ‘musical armor’ against these predators. The discovery of such a ‘musical battle’ between fireflies and bats may pave the way for further research, and the discovery of a new defense mechanism developed by animals against their predators. According to the study, the fireflies produce strong ultrasonic sounds soundwaves that the human ear, and more importantly the fireflies themselves, cannot detect. The researchers hypothesize that these sounds are, in fact, meant for the ears of the bats, keeping them away from the poisonous fireflies, and thereby serving as a kind of ‘musical armor’. The study was led by Prof. Yossi Yovel, Head of the Sagol School of Neuroscience, and a member of the School of Mechanical Engineering and the School of Zoology at the George S. Wise Faculty of Life Sciences. It was conducted in collaboration with the Vietnam Academy of Science and Technology (VAST) and has been published in iScience. Fireflies are known for their unique, all-year glow, which is effective as a mating signal. Their bodies contain poison, and so the light flashes probably also serve as an aposematic signal, a warning to potential predators. At the same time, this signal is also the firefly’s weakness, as it makes it an easy target for predators. Bats are among the fireflies’ most prevalent potential predators, and some bats have poor vision, rendering the flashing signal ineffective. This prompted the researchers to check whether fireflies were equipped with an additional layer of protection against bats.

Accidental Discovery of ‘Musical Battle’

The idea for this study came up accidentally, during a study that tracked bats’ echolocation. Ksenia Krivoruchku, the PhD student who led the study recalls, “We were wandering around a tropical forest with microphones capable of recording bats’ high frequencies, when suddenly, we detected unfamiliar sounds at similar frequencies, coming from fireflies. “In-depth research, using high-speed video, revealed that the fireflies produce the sound by moving their wings, and that the fireflies themselves are incapable of hearing this frequency. Consequently, we hypothesized that the sound is not intended for internal communication within the species.” Following this discovery, the team at Prof. Yovel’s laboratory examined three different species of fireflies that are common in Vietnam (Curtos, Luciola and Sclerotia), in addition to one Israeli species (Lampyroidea). It was found that they all produce these unique ultrasonic sounds, and that they are all unable hear them. Prof. Yovel says that it is premature to conclude that fireflies have developed a special defense mechanism specifically targeting bats, there are indications that this may be the case. The fact that the fireflies themselves are unable to hear the sound, while bats can both hear it and use it to detect the fireflies, makes it more likely that these ultrasonic sounds serve as a warning signal. The discovery of ultrasonic sounds in fireflies is in itself an important contribution to the study of predator-prey relations. The idea of warning signals that the sender itself cannot detect is known from the world of plants, but is quite rare among animals. Krivoruochku says “Our discovery of the ‘musical battle’ between fireflies and bats may pave the way for further research, and possibly the discovery of a new defense mechanism developed by animals against potential predators.”

Why Do Bats Fly Into Walls?

A sensory misperception – like people bumping into a glass wall

Why do bats fly into walls, even though they can hear them? Researchers at Tel Aviv University conducted an experiment in which they released dozens of bats in a corridor blocked by objects of different sizes, made of different materials. To their surprise, the researchers discovered that the bats collided with large sponge walls (that produce a weak echo) as if they did not exist. The bats’ behavior suggested that they did this even though they had detected the wall with their sonar system, indicating that the collision did not result from a sensory limitation, but rather from an acoustic misperception. The researchers hypothesize that the unnatural combination of a large object (wall) and a weak echo disrupts the bats’ sensory perception and causes them to ignore the obstacle (much like people who bump into transparent walls).

The study was led by Dr. Sasha Danilovich then a PhD student in the lab of Prof. Yossi Yovel, Head of the Sagol School for Neuroscience and faculty member at the School of Zoology at the George S. Wise Faculty of Life Sciences. Other participants included Dr. Arian Bonman and students Gal Shalev and Aya Goldstein of the Sensory Perception and Cognition Laboratory at the School of Zoology and the Sagol School of Neuroscience. The paper was published in PNAS.

At the next stage of the experiment, the researchers methodically changed the features of the echoing objects along the corridor in terms of size, texture and echo intensity. They concluded that the bats’ acoustic perception depends on a coherent, typical correlation of the dimensions with objects in nature. For example: large object- strong echo; small object – weak echo.

“Bats excel in acoustic perception. They are able to detect objects as tiny as mosquitoes, using sound waves,” explains Prof. Yovel. “Using echolocation they can calculate the 3-dimensional location of both small and large objects, perceiving their shape, size and texture. To this end a bat’s brain processes various acoustic dimensions from the echoes returning from the object (such as frequency, spectrum and intensity). This perception is based on several senses that combine many different dimensions, such as color and shape.”

In addition, the researchers at TAU discovered that bats are not born with this ability. Repeating the experiment with young bats they found that they do not fly into walls.  The study also found that adult bats can quickly learn the new correlations among the dimensions.

“By presenting the bats with objects whose acoustic dimensions are not coherent, we were able to mislead them, creating a misconception that caused them to repeatedly try to fly through a wall, even though they had identified it with their sonar. The experiment gives us a peek into how the world is perceived by these creatures, whose senses are so unique and different from ours,” says Sasha Danilovich.

TAU Prof. Wins Schmidt Science Polymath Award

Prof. Oded Rechavi one of first winners of prestigious prize, which is defined as “an experiment in extreme curiosity-driven innovation”

A great honor for Israeli science: Schmidt Futures, a philanthropic initiative founded by Eric and Wendy Schmidt,  has decided to establish a new $2.5m award entitled Polymaths, for researchers exhibiting rare interdisciplinarity. Only two scientists have been chosen to receive the first Polymaths Award: Prof. Jeff Gore of MIT and Prof. Oded Rechavi of the Neurobiology Department at the George S. Wise Faculty of Life Sciences and the Sagol School of Neuroscience at Tel Aviv University. Each of the two scientists will receive an annual unrestricted grant of $500,000 for five years, to pursue any direction of research. “I am proud to have been chosen and excited about the opportunity to open new fields of research,” says Prof. Rechavi. “Typically scientists receive funds for research projects that are already underway. The Polymaths Award is different. They tell you: ‘Here are the resources. Do something completely new, take risks. Investigate wild ideas you never would have dreamed of proposing to other research foundations.'”

The Schmidt Science Polymath program is an initiative created under Schmidt Futures, which finds exceptional people and helps them achieve more for others by applying advanced science and technology thoughtfully and by working together across fields. The program aims to provide outstandingly interdisciplinary researchers with the means to expand their research even further. In the future, a prestigious network of the award’s laureates will be established. “An experiment in extreme curiosity-driven innovation,” proclaims the program. “Instead of focusing on specific research ideas, the goal for the program is to bet on people, their special talents, and their teams.” 

The laboratory of the first Polymath Award laureate, Prof. Oded Rechavi, excels in promoting interdisciplinary research. In recent years Prof. Rechavi has studied a very vast range of topics, achieving scientific breakthroughs in fields that are not necessarily connected to one another. Thus, for example, Rechavi discovered a mechanism enabling transgenerational inheritance of parental responses, showing for the first time that small RNAs are inherited alongside DNA, and deciphering the laws of epigenetic heredity. In another study, Rechavi and his team assisted in decoding the Dead Sea Scrolls through the DNA of the parchments on which they were written, shedding more light on the history of the late Second Temple period. Rechavi also explored the neuronal basis of irrationality, finding a simple law for altering the nervous system of worms so that they become less or more rational. In a completely different area, Rechavi’s group genetically engineered parasites to turn them into protein-secreting machines enabling repair of genetic diseases of the nervous system.

Prof. Oded Rechavi. Photo: Yehonatan Zur.

How the parents’ environment impacts the lives of their offspring

Three rules that dictate transgenerational epigenetic inheritance in worms – independently of changes in DNA sequences.

Researchers at Tel Aviv University have discovered three rules that dictate epigenetic inheritance – meaning transgenerational inheritance through means other than changes in DNA sequences. Published today in the leading scientific journal Cell, the study was led by Prof. Oded Rechavi and his research student Dr. Leah Houri-Zeevi of the Department of Neurobiology at the Faculty of Life Sciences and the Sagol School of Neuroscience at Tel Aviv University.

Most experiences we acquire in our lifetime will not be passed on to our descendants. For example, our workout in the gym today will not make our children stronger. However, studies conducted in recent years on epigenetic inheritance in worms challenge our traditional concepts regarding the limits of inheritance and evolution, indicating that some acquired traits are in fact passed on to subsequent generations. Prof. Rechavi explains: “Epigenetic inheritance of responses to the environment occurs independently of changes to the DNA sequence, through other inherited molecules. In many organisms, responses to environmental changes, such as stress, involve small RNA molecules that silence or block the expression of certain genes.” In recent years, research on C. elegans worms – an important and widely used model animal – has shown that small RNA molecules can be transmitted to subsequent generations, thereby passing on certain traits.

In previous research projects, Prof. Rechavi discovered that worms transfer to their offspring small RNA molecules containing information on the parent’s environment, such as viral infections, nutrition, and even brain activity, thereby contributing to the survival of subsequent generations. In the current study, Prof. Rechavi and his team tried to understand whether transgenerational epigenetic inheritance via small RNA molecules is governed by specific rules, or alternately, occurs passively and randomly.

According to Prof. Rechavi, “C. elegans is the preferred model organism for research on transgenerational epigenetic inheritance, for several  reasons: Its generation time is three and a half days, allowing us to study many generations in a short period of time; every worm produces hundreds of descendants, providing strong statistical validity; environmental exposure can be fully controlled; and each worm fertilizes itself, so that differences in DNA are almost completely neutralized.”

Dr. Houri-Zeevi explains that “Many laboratories have noted that at the level of a population epigenetic inheritance through small RNA endures for about three to five generations in worms. In a previous study, we discovered a mechanism that controls the duration of the inheritance, proving, in effect, that this type of inheritance is a regulated process. But still the question remains: Why are some worms strongly affected by their ancestor’s environmental responses, while others do not inherit the epigenetic effect at all – despite the fact that all offspring are almost identical genetically. This partial inheritance has been known for some time, but how epigenetic material is distributed among the offspring remained a mystery. We wanted to find out whether there was any pattern in the inheritance, that might explain and allow us to predict who would inherit the epigenetic features – and for how long.”

The researchers used a genetically engineered worm carrying a gene that produces a fluorescent protein – making the worm itself glow under fluorescent light. The researchers then initiated a heritable small RNA silencing response against the fluorescent gene and observed which descendants had inherited the silencing response and stopped glowing, and which descendants ‘forgot’ the parental response and started expressing the fluorescent gene once again after several generations. Dr. Houri-Zeevi repeated this process over and over again, in an attempt to understand the rules governing the epigenetic effect. Altogether she examined dozens of worms lineages, including more than 20,000 individual worms. But the most challenging part, according to Prof. Rechavi, was deciphering the different inheritance patterns and understanding the rules behind them.

Ultimately, through in-depth investigation of the inheritance mechanism, the researchers discovered three laws that can explain and even enable the prediction of who inherits the epigenetic information:

  • First law: Inheritance is uniform in worms descending from the same mother – namely worms of the same lineage. The researchers were surprised to learn that differences in inheritance observed in previous studies were in fact ‘concealed’ due to the method of examining whole worm populations rather than distinct lineages.
  • Second law: Inheritance is very different in worms derived from different mothers, even though the mothers themselves are supposedly identical, because the worm fertilizes itself. The researchers characterized the mechanism that creates the differences between mothers who are genetically identical and found that differences between descendants stem from varying ‘internal states’ randomly adopted by the mothers. Essentially, the mother’s internal state, the level of activity of the inheritance mechanism in each mother, determines the duration of inheritance, and thus the fate of subsequent generations.
  • Third law: The longer the duration of the epigenetic inheritance – namely, the greater the number of generations in a specific lineage who inherits the trait – the greater the probability that it will continue on to the next generation as well, “in something like transgenerational momentum, resembling the ‘Hot Hand’ rule in basketball.”

According to Prof. Rechavi, we do not yet know whether the exact same transgenerational epigenetic inheritance mechanism exists in humans as well: “We hope that the mechanism we have discovered exists in other organisms as well, but we’ll just have to be patient. We must remember that genetic research also began with Friar Gregor Mendel’s observations in peas, and today we use Mendel’s laws to predict whether our children will have smooth or curly hair.”

“The idea of acquired traits passed on to descendants is as old as it is outrageous. Even before Darwin and Lamarck, the ancient Greeks argued about it, and it seems to be incompatible with genetic inheritance through DNA,” adds Prof. Rechavi. “The worms changed the rules by showing us that inheritance outside the genetic sequence does exist, via small RNA molecules, enabling parents to prepare their offspring for the difficulties they have encountered in their lifetime. From one study to the next we shed light on the molecular mechanisms and mysterious dynamics of epigenetic inheritance, with the present study providing laws and introducing some ‘order into the chaos’.”

Does our Brain like risk?

A new study attempts to find out whether our brains are prone to over caution or to underestimating risk

A new Tel Aviv University study examined the brain’s reactions in conditions of uncertainty and stressful conflict in an environment of risks and opportunities. The researchers identified the areas of the brain responsible for the delicate balance between desiring gain and avoiding potential loss along the way.

The study was led by Tel Aviv University researchers Prof. Talma Hendler, Prof. Itzhak Fried, Dr. Tomer Gazit, and Dr. Tal Gonen from the Sackler Faculty of Medicine, the School of Psychological Sciences and the Sagol School of Neuroscience, along with researchers from the the Tel Aviv Sourasky Medical Center (Ichilov) and the University of California, Los Angeles School of Medicine. The study was published in July 2020 in the prestigious journal Nature Communications.

Prof. Hendler explains that in order to detect reactions in the depths of the brain, the study was performed among a unique population of epilepsy patients who had electrodes inserted into their brains for testing prior to surgery to remove the area of the brain causing epileptic seizures. Patients were asked to play a computer game that included risks and opportunities, and the electrodes allowed the researchers to record, with a high level of accuracy, neural activity in different areas of the brain associated with decision-making, emotion and memory.

Your brain suggests – play it safe

Throughout the game, the researchers recorded the electrical activity in the subjects’ nerve cells immediately after they won or lost money. The subjects were asked to try to collect coins while taking the risk of losing money from their pool. It was found that the neurons in the area of ​​the inner prefrontal cortex responded much more to loss (punishment) than to the gaining (reward) of coins.

Moreover, the researchers found that the avoidance of risk-taking in the players’ next move was affected mainly by post-loss activity in the area of the hippocampus, which is associated with learning and memory, but also with anxiety. This finding demonstrates the close relationship between memory processes and decision-making when risk is present (stressful situations). That is, the loss is encoded in the hippocampus (the region of the brain associated with ​​memory), and the participant operating in a high-risk stressful situation preferred to be cautious and avoid winning the coins (forfeiting the gain).

The experience of winning, however, was not encoded in the memory in a way that influenced the choice of future behavior in conditions of uncertainty. An interesting point is that this phenomenon was found only when the subject was the once influencing the result of the game, and only in the presence of a high risk in the next move, which indicates a possible connection to anxiety.

Prof. Hendler summarizes: “Throughout life, we ​​learn to balance the fear of risking loss with the pursuit of profit, and we learn what is a reasonable risk to take in relation to the gain based on previous experiences. The balance between these two tendencies is a personality trait but is also affected by stress (like the current pandemic). A disorder in this trait increase sensitivity to stress and can cause non-adaptive behavior such as a high propensity for risk-taking or excessive avoidance.

“Our research shows for the first time how the human brain is affected by the experience of failure or loss when it is our responsibility, and how this inclination produces avoidance behavior under particularly stressful uncertainty. An understanding of the neural mechanism involved may guide future neuropsychiatric therapies for disorders featuring excessive avoidance, such as depression, anxiety, and PTSD, or disorders associated with excessive risk-taking, such as addiction and mania.”

Featured image: Prof. Talma Hendler

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