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Tag: Neuroscience

While You Were Sleeping

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Could we be one step closer to verifying whether a seemingly unconscious person is truly unaware of his or her surroundings?

A new TAU discovery may provide a key to a great scientific enigma: How does the awake brain transform sensory input into a conscious experience? The researchers were surprised to discover that the brain’s response to sound remains powerful during sleep in all parameters but one: the level of alpha-beta waves associated with attention to the auditory input and related expectations. This means that during sleep, the brain analyzes the auditory input but is unable to focus on the sound or identify it, and therefore no conscious awareness ensues.

The study was led by Dr. Hanna Hayat and with major contribution from Dr. Amit Marmelshtein, at the lab of Prof. Yuval Nir from the School of Medicine of the Sackler Faculty of Medicine, the Sagol School of Neuroscience, and the Department of Biomedical Engineering, and co-supervised by Prof. Itzhak Fried from the UCLA Medical Center. Other participants included: Dr. Aaron Krom and Dr. Yaniv Sela from Prof. Nir’s group, and Dr. Ido Strauss and Dr. Firas Fahoum from the Tel Aviv Sourasky Medical Center (Ichilov). The paper was published in the prestigious journal Nature Neuroscience.

A Deep Dive into the Human Brain

Prof. Nir explains that this study is unique in that it builds upon rare data from electrodes implanted deep inside the human brain, enabling high-resolution monitoring, down to the level of individual neurons, of the brain’s electrical activity.

While electrodes cannot be implanted in the brain of living humans just for the sake of scientific research, in this case the researchers were able to utilize a special medical procedure in which electrodes were implanted in the brains of epilepsy patients, monitoring activity in different parts of their brain for purposes of diagnosis and treatment. The patients volunteered to help examine the brain’s response to auditory stimulation in wakefulness versus sleep.

The researchers placed speakers emitting various sounds at the patients’ bedside and compared data from the implanted electrodes – neural activity and electrical waves in different areas of the brain – during wakefulness and during various stages of sleep. Altogether, the team collected data from over 700 neurons (about 50 neurons in each patient) over the course of 8 years.

 

Dr. Hanna Hayat

Measuring the Strength of Alpha-beta Waves

“After sounds are received in the ear, the signals are relayed from one station to the next within the brain,” explains Dr. Hayat. “Until recently it was believed that during sleep these signals decay rapidly once they reach the cerebral cortex.  But looking at the data from the electrodes, we were surprised to discover that the brain’s response during sleep was much stronger and richer than we had expected. Moreover, this powerful response spread to many regions of the cerebral cortex. The strength of brain response during sleep was similar to the response observed during wakefulness, in all but one specific feature: the level of activity of alpha-beta waves.”

The researchers explain that alpha-beta waves (10-30Hz) are linked to processes of attention and expectation that are controlled by feedback from higher regions in the brain. As signals travel ‘bottom-up’ from the sensory organs to higher regions, a ‘top-down’ motion also occurs: the higher regions, relying on prior information that had accumulated in the brain, act as a guide, sending down signals to instruct the sensory regions as to which input to focus on, which should be ignored, etc. Thus, for example, when a certain sound is received in the ear, the higher regions can tell whether it is new or familiar, and whether it deserves attention or not.

“We hope that our findings will serve as a basis for developing effective new methods for measuring the level of awareness of individuals who are supposedly in various states of unconsciousness.”

This kind of brain activity is manifested in the suppression of alpha-beta waves, and indeed, previous studies have shown a high level of these waves in states of rest and anesthesia. According to the current study, the strength of alpha-beta waves is the main difference between the brain’s response to auditory inputs in states of wakefulness vs. sleep.

Decoding Consciousness

Prof Nir summarizes: “Our findings have wide implications beyond this specific experiment. First, they provide an important key to an ancient, fascinating enigma: What is the secret of consciousness? What is the ‘X-factor’, the brain activity that is unique to consciousness, allowing us to be aware of things happening around us when we are awake, and disappearing when we sleep? In this study we discovered a new lead, and in future research we intend to further explore the mechanisms responsible for this difference. 

“In addition, having identified a specific brain feature that is different between states of consciousness and unconsciousness, we now have a distinct quantitative measure – the first of its kind – for assessing an individual’s awareness of incoming sounds. We hope that in the future, with improved techniques for measuring alpha-beta brain waves, and non-invasive monitoring methods such as EEG, it will be possible to accurately assess a person’s state of consciousness in various situations: verifying that patients remain unconscious throughout a surgical procedure, monitoring the awareness of people with dementia, or determining whether an allegedly comatose individual, unable to communicate, is truly unaware of his/her surroundings. In such cases, low levels of alpha-beta waves in response to sound could suggest that a person considered unconscious may in fact perceive and understand the words being said around him. We hope that our findings will serve as a basis for developing effective new methods for measuring the level of awareness of individuals who are supposedly in various states of unconsciousness. “

 

Outstanding Navigators, both Night and Day

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Researchers find that bats navigate well, also during the day, thanks to their unique sensory integration.

It is time to bust a myth about bats – bats actually see well during the day and they know how to navigate the space during daylight hours. A new Tel Aviv University study has found that fruit bats use their biological sonar during the day, even though their vision is excellent and would ostensibly eliminate the need for the bats to emit calls to the environment and use their echoes to locate objects (echolocation). The researchers believe that due to the high accuracy of the bats’ bio-sonar system in estimating how far objects are, echolocation offers an additional tool – on top of vision – to help ensure that the bats are navigating as effectively as possible. This is similar to a person crossing the street using their sense of hearing as well as sight to make sure the road is clear.

Enjoying the Tel Aviv Sun

The study was conducted under the supervision of Prof. Yossi Yovel, head of Tel Aviv University’s Sagol School of Neuroscience and a researcher at the School of Zoology in The George S. Wise Faculty of Life Sciences and the Steinhardt Museum of Natural History. The study was led by Ph.D. student Ofri Eitan in cooperation with Dr. Maya Weinberg, Dr. Sasha Danilovich, and Reut Assa, all from Tel Aviv University, and Yuval Barkai, an urban nature photographer. The study will be published in the journal Current Biology.

The researchers explain that in general, bats are active mainly at night, and echolocation is the tool they use to navigate their way in the dark. They also say, however, that in recent years a growing phenomenon has been witnessed in Israel, particularly in Tel Aviv but also in other cities, in which Egyptian fruit bats roam around even during the day. In the current study, the researchers sought to examine what happens when the bats are active during the day, and whether they are aided by their unique bio-sonar even in conditions of good visibility.

For the first time, the researchers studied the activity and sensory behavior of the fruit bat during the day. The research was conducted with the help of photography and audio recordings of the bats’ activities throughout the day, in three different situations: in the morning, as they went out to explore in Tel Aviv; later in the day, when they visited Tel Aviv’s sycamore trees; and while they were drinking water from an artificial pool. In each of these situations, the bats used echolocation.

Daytime Integration of Senses

Ofri Eitan explains: “We compared the bats’ landings and flights between the trees, and found that prior to landing, the bats increased the sounds they emitted in order to use the echoes to help estimate the distance to the ground. In addition, we found that even in the pools of water, bats increased the rate of their calls before coming into contact with the water and reduced it (and sometimes even ceased the calls completely) after ascending from the water to fly to an open area. On the other hand, there were cases in which the bats emerged from the pool and had a wall placed in front of them, and once again returned to the use of echolocation. So, all our results show that the fruit bats make functional use of echolocation.”

Prof. Yossi Yuval concludes: “Our results are unequivocal and show that fruit bats make frequent use of echolocation even during the day when visibility is good. We hypothesize that this is due to the fact that echolocation helps the bats to measure the distances of objects in the environment more accurately, and that their brains combine the visual information along with the auditory information. This study shows how important integration between different senses is, just as we humans integrate visual and auditory information when we cross a street, for example.”

TAU Researchers Find Gene Mechanism Linked to Autism and Alzheimer’s

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Experimental drug has potential to treat rare syndromes that impair brain functions.

Researchers at Tel Aviv University, led by Prof. Illana Gozes from the Department of Human Molecular Genetics and Biochemistry at the Sackler Faculty of Medicine and the Sagol School of Neuroscience, have unraveled a mechanism shared by mutations in certain genes which cause autism, schizophrenia, and other conditions. The researchers also found that an experimental drug previously developed in Prof. Gozes’ lab is effective in lab models for these mutations, and believe the encouraging results may lead to effective treatments for a range of rare syndromes that impair brain functions and cause autism, schizophrenia, and neurodegenerative diseases like Alzheimer’s.

“Some cases of autism are caused by mutations in various genes,” explains Gozes. “Today, we know of more than 100 genetic syndromes associated with autism, 10 of which are considered relatively common (though still extremely rare). In our lab, we focus mainly on one of these, the ADNP syndrome. The ADNP syndrome is caused by mutations in the ADNP gene, which disrupt the function of the ADNP protein, leading to structural defects in the skeleton of neurons in the brain. In the current study, we identified a specific mechanism that causes this damage in mutations in two different genes: ADNP and SHANK3 – a gene associated with autism and schizophrenia. According to estimates, these two mutations are responsible for thousands of cases of autism around the world.”

To start with, the researchers obtained cells from patients with ADNP syndrome. They discovered that when the ADNP protein is defective, neurons with faulty skeletons (microtubules) are formed, impairing brain functions. They also found, however, that ADNP mutations take different forms, some of which cause less damage.

Gozes explains that in some mutations, a section added to the protein protects it and reduces the damage by connecting to a control site of the neuron’s skeletal system and that this same control site is found on SHANK3 – a much studied protein, with mutations that are associated with autism and schizophrenia. “We concluded that the ability to bond with SHANK3 and other similar proteins provides some protection against the mutation’s damaging effects,” she says.

At the next stage of the study, the researchers found additional sites on the ADNP protein that can bond with SHANK3 and similar proteins. One of these sites is located on NAP, a section of ADNP which was developed into an experimental drug, called Davunetide, by Prof. Gozes’ lab.

Moreover, the researchers demonstrated that extended treatment with Davunetide significantly improved the behavior of lab animals with autism caused by SHANK3.

“In previous studies we showed that Davunetide is effective for treating ADNP syndrome models. The new study has led us to believe that it may also be effective in the case of Phelan McDermid syndrome, caused by a mutation in SHANK3, as well as other syndromes that cause autism through the same mechanism,” explains Gozes.

Participants in the study: Dr. Yanina Ivashko-Pachima, Maram Ganaiem, Inbar Ben-Horin-Hazak, Alexandra Lobyntseva, Naomi Bellaiche, Inbar Fischer, Gilad Levy, Dr. Shlomo Sragovich, Dr. Gidon Karmon, and Dr. Eliezer Giladi from the Sackler Faculty of Medicine and Sagol School of Neuroscience at TAU, Dr. Boaz Barak from The School of Psychological Sciences, Gershon H. Gordon Faculty of Social Sciences and the Sagol School of Neuroscience at TAU, and Dr. Shula Shazman from the Department of Mathematics and Computer Science at the Open University. The paper was published in the scientific journal Molecular Psychiatry.

Can Higher Temperatures Accelerate the Rate of Evolution?

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TAU researchers use worms to demonstrate that epigenetic inheritance of sexual attractiveness can impact the evolutionary process.

Can environment impact genetic diversity in face of changing conditions, such as higher temperatures (think global warming)? Researchers at Tel Aviv University have discovered that epigenetic inheritance – inheritance which does not involving changes in the DNA sequence – can affect the genetic composition of the population for many generations. The environment can actually impact genetic diversity under certain conditions and the researchers believe that it’s a way for the environment to adjust genetic diversity.

Worms Get It from their Mama’s Mama’s Mama’s… 

Females of the worm species C. elegans produce both egg cells (or “oocytes”) and sperm, and can self-reproduce (hence are considered hermaphrodites). They produce their sperm in a limited amount, only when they are young. At the same time, there are also rare C. elegans males in the population that can provide more sperm to the female worms through mating.

In normal conditions, the female hermaphrodites secrete pheromones to attract males for mating only when they grow old and run out of their own sperm (at this point mating becomes the only way for them to continue and reproduce). Therefore, when the hermaphrodite is young, and still has sperm, she can choose whether to mix her genes by sexually reproducing with a male, or not.

In the new study, exposure to elevated temperatures was found to encourage more hermaphrodites to mate, and this trait was also preserved in the offspring for multiple generations, even though they were raised in comfortable temperatures and did not experience the stress from the increased heat.

The study, which was published today in the journal Development Cell, was led by Prof. Oded Rechavi and Dr. Itai Toker, as well as Dr. Itamar Lev and MD-PhD student Dr. Yael Mor, who did their doctorates under Prof. Rechavi’s supervision at the School of Neurobiology, Biochemistry & Biophysics, George S. Wise Faculty of Life Sciences, and the Sagol School of Neuroscience. The study was conducted in collaboration with the Rockefeller University in New York.

Securing Genetic Diversity

Why did the higher temperatures result in the C. elegans worms becoming more attractive, mating more with males? Dr. Itai Toker explains that “The heat conditions we created disrupted the inheritance of small RNA molecules that control the expression of genes in the sperm, so the worm’s sperm was not able to fertilize the egg with the efficiency that it normally would. The worm sensed that the sperm it produced was partially damaged, and therefore began to secrete the pheromone and attract males at an earlier stage, while it was still young.”

If that wasn’t enough, Dr. Rechavi points out that the really fascinating finding was that the trait of enhanced attractiveness was then passed on for many generations to offspring who did not experience the conditions of higher temperatures. The researchers found that heritable small RNA molecules, not changes in the DNA, transmitted the enhanced attractiveness between generations. Small RNAs control gene expression through a mechanism known as RNA interference or gene silencing – they can destroy mRNA molecules and thus prevent specific genes from functioning in a given time at a given tissue or cell.

Dr. Itai Toker adds that, “In the past, we discovered a mechanism that passes on small RNA molecules to future generations, in parallel and in a different way from the usual DNA-based inheritance mechanism. This enables the transmission of certain traits transgenerationally. By specifically inhibiting the mechanism of small RNA inheritance, we demonstrated that the inheritance of increased attractiveness depends on the transmission of small RNAs that control sperm activity.”

Mating, as opposed to fertilizing themselves, comes at a price for the female, hermaphroditic worms, as it allows them to pass on only half of their genome to the next generation. This “dilution” of the parents’ genetic contribution is a heavy price to pay. The benefit, however, is that it increases genetic diversity. By conducting lab evolution experiments we indeed discovered that it may be a useful adaptive strategy.

The researchers later experimented with evolution: They tracked the offspring of mothers who passed on the trait of attractiveness to males with the help of small RNAs, and allowed them to compete for males, for many generations, against normal offspring from a control group. The researhers observed how the inheritance of sexual attractiveness led to more mating in these competitive conditions, and that as a result the attractive offspring were able to spread their genes in the population more successfully.

 

Prof. Oded Rechavi (photo: Yehonatan Zur Duvdevani)

Environment’s Response to Global Warming?

In general, living things respond to their environment by changing their gene expression, without changing the genes themselves. The understanding that some of the epigenetic information, including information about the parents’ responses to environmental challenges, is encoded in small RNA molecules and can be passed down from generation to generation has revolutionized our understanding of heredity, challenging the dogma that has dominated evolution for a century or more. However, to date researchers have not been able to find a way in which epigenetic inheritance can affect the genetic sequence (DNA) itself.

“Epigenetics in general, and the inheritance of parental responses facilitated by small RNAs in particular, is a new field that is garnering a lot of attention,” says Dr. Lev. “We have now proven that the environment can change not only the expression of genes, but, indirectly, also genetic heredity, and for many generations.”

“Generally, epigenetic inheritance of small RNA molecules is a transient matter: the organism is exposed to a particular environment, and preserves the epigenetic information for 3-5 generations. In contrast, evolutionary change occurs over hundreds and thousands of generations. We looked for a link between epigenetics and genetics and found that a change in the environment, that is relevant to global warming, induces transgenerational secretion of a pheromone to attract males, and thus affects the evolution of the worms’ genome.”

Dr. Mor adds, “We think that it’s a way for the environment to adjust genetic diversity. After all, evolution requires variability and selection. The classical theory is that the environment can influence selection, but cannot affect variability, which is created randomly as a result of mutations. We found that the environment can actually impact genetic diversity under certain conditions.”

How Do Bats Get Street-Smart?

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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?

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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

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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

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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

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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

Written by AUFTAU on . Posted in Newsroom.

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.”
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