Duke Research Blog

Following the people and events that make up the research community at Duke.

Category: Animals (Page 1 of 13)

Meet New Blogger Brian Du

Brian survives his week in the desert.

Hi! My name is Brian Du, and I’m a sophomore from Texas. I’m a pre-med majoring in computer science. I like vacations, hiking, and hiking on vacation. Besides these hobbies, I also love learning about science and hearing a good story. These latter two are exactly why I’m excited to be writing for the Duke Research Blog.

My first exposure to science happened in third grade because my goldfish kept getting sick and dying. This made me sad and I became invested in making them well again. I would measure pH levels regularly with my dad and keep notes on the fishes’ health. Eventually the process turned into a science fair project. I remember I loved presenting because I got to point out to the judges the ‘after’ pictures of my fish, which showed them alive, healthy, and happy (I think? it’s hard to tell with fish).

One happy fish!
Source: Reddit

My fish and I go way back.

After that third-grade experiment, I kept doing science projects — almost year after year actually — since I love the research process. From framing the right questions and setting up the experiment, to running the trials and writing up and sharing my work, my enthusiasm grew with each step. Come competition day, I noticed that in interviews that went well, my excitement was contagious, so that judges grew more eager too as they listened. And so I understood: a huge part to science is communication. Science, like food or a good story, is meant to be shared with others. The scientist is a storyteller, adjusting his presentation to captivate different audiences. With judges, I spoke jargon, but during public exhibition, where I chatted with anyone who came up to me, I got creative when asked about my research. Analogies helped me link strange concepts to everyday objects and experiences. An important protein channel became a pipe, and its inhibitor molecule a rock which would clog the pipe to make it unusable.

protein channel “pipe”
edited from CThompson02

Now that I’m at Duke, there’s so many stories to tell of the rich variety of research being done right on campus! I’ve written a few articles for the Chronicle covering some of the new medicine or proteins Duke professors have been involved in developing. As I keep an ear out for more stories, I hope to share a few of them in my upcoming posts, because I know they’ll be exciting!

New Blogger Rebecca Williamson: The Moon and Some Stars

Hello! My name is Rebecca Williamson, and I am a freshman here at Duke University. Coming into college, I plan to major in economics, but that could very well change. As for my interests outside of the classroom, I enjoy singing and theater and am a member of Out of the Blue, one of the all-female a cappella groups here at Duke!

Rebecca Williamson, Duke 2022

Rebecca Williamson, Duke 2022

I fell in love with Duke the second I stepped on campus. I am excited to see what Duke has to offer me, but more importantly, what I can offer to Duke.

My interest in science, specifically astronomy, was piqued at a very young age. By age six, I had not one, but three,  Moon in my Room light up toys (remote controlled models of the Moon that scrolled through the waxing and waning phases of the Moon at the touch of a button) mounted in my bedroom. By nine, I had the entire planetary system (yes, including Pluto) hanging from my ceiling. Though I cannot say that my interests remain with astronomy, it is what first got me invested in science. I have since gained interest in the natural sciences and animal sciences, though every so often I do press some of the buttons on my Moon in my Room remote.

Some random boy imagines he's as cool as six-year-old Rebecca.

Some random boy imagines he’s as cool as six-year-old Rebecca.

My love of writing, however, was spawned by my love of theater. As an active member of my high school’s theater community, I was roped into being a part of, and eventually became the president, of my school’s Cappies Critics team. As a Cappie, I was expected to watch local high school plays and musicals and write critical, holistic reviews of them. This program jump-started my love for writing and helped me to develop my own unique journalistic voice.

solar system mobile. www.luxrysale.comI hope to combine my interest in the natural and animal sciences with my love for writing and chronicle some of the amazing research going on in these fields both on campus and around Durham! I also hope to incorporate my interests in music and theater into my inquiries and document scientific research surrounding music and the arts in the Duke community.

Duke University Research Blog, look out, because here I come!

Post by Rebecca Williamson

The Complicated Balance of Predators and Prey

If you knew there was a grizzly bear sitting outside the door, you might wait a while before going to fill up your water bottle, or you might change the way you are communicating with their other people in the room based on your knowledge of the threat.

Ecologists call this “predation risk,” in which animals that could potentially fall prey to a carnivore know this risk is present, and alter their habits and actions accordingly.

A yellow slider turtle.

A yellow slider turtle.

One way in which animals do this is through habitat use, such as a pod of dolphins that changes where they spend most of their time depending on the presence or absence of predators. Animals might also change their feeding habits and diving behavior because of predation risk.

Animals do this all of the time in the wild, but when predators are removed from ecosystems by hunting or over-fishing, the effect of their absence is felt all the way down the food chain.

For example, large amounts of algae growth on coral reefs can be traced back to over-fishing of large ocean predators such as sharks, who then don’t hunt smaller marine mammals like seals. As seal numbers increase, there are more of them to hunt smaller fish that feed on vegetation, which means fewer smaller fish or plankton to keep algal growth in check, and algae begins to grow unchecked.

Meagan Dunphy-Daly

Meagan Dunphy-Daly

This is a “trophic cascade” and it has large effects on ecosystems, Duke Marine Lab instructor Meagan Dunphy-Daly  t0ld the Sustainable Oceans Alliance last Thursday. She has performed research both in labs and in the field to study the effects that removing large predators have on marine ecosystems.

Dunphy-Daly discussed one lab experiment where 10 yellow-bellied slider turtle hatchlings were kept in tanks where they couldn’t see people or anything else on the outside. In real life, blue herons and other large birds prey on these turtle hatchlings, so the researchers made a model skull of a blue heron that they painted and covered with feathers.

Turtles are air-breathing, so each hatchling was given the option to sit where they could be at the surface of their tank and breathe, but this spot was also where the turtle hatchlings thought the bird beak might shoot down at any time to try to “eat” them.

Their options were to get air and risk getting hit by the bird beak, or diving down to the bottom of the tank to get food. During this experiment, Dunphy-Daly found that turtle hatchlings actually decreased their dive time and spent more time at the surface. If the turtles are continuously diving, they are expending lots of energy swimming back and forth between the surface and the bottom, she said, which means if the predator were to actually attack, they would have less energy left to use for a rapid escape.

Even when there is food at the bottom, when a predator is present, these turtles alter their activity by taking deep dives less frequently so as to not max out their aerobic limit before they actually need to escape a predator.

This is one way in which animals alter their behavior due to predation risk.

But let’s say that predators were disappearing in their real habitats, so turtles didn’t feel the need to build up these emergency energy reserves to escape them. They might dive down and feed more frequently, which would then decrease the amount of the vegetation they eat.

This in turn could have an effect on oxygen levels in the water because there would be fewer plants photosynthesizing. Or another species that feeds on the same plant could be out-competed by turtles and run out of food for their own populations.

The absence of large or small predators can have large impacts on ocean ecosystems through these complicated trophic cascades.

Victoria PriesterPost by Victoria Priester

New Blogger: Victoria Priester Loves Animals and Books

Hi! My name is Victoria Priester, and I’m a sophomore at Duke and one of this year’s new Duke Research bloggers.

Victoria meeting a very intelligent mammal.

I’m pre-vet, but I’ve always been a bookworm and have a love for expressing myself through writing that has given me a strained relationship with word counts. I’ll try to keep this intro post brief!

I’m majoring in English in addition to taking pre-veterinary classes, so my time in the library so far this year has been spent alternating between drawing resonance structures for organic chemistry and reading Jane Eyre in the Gothic Reading Room, which is my favorite study spot on campus.

Effective puppy medicine includes hugging and kissing.

I grew up in the suburbs of Washington, D.C. and now I work in the veterinary department at Duke Lemur Center. I’m also an editor and opinion columnist for The Chronicle. My favorite part of the academic scene at Duke is that pursuing such different interests at the same time is encouraged.

This year, I’m a part of the Bass Connections team that is studying how using expressive writing for resilience can help cancer patients process their experiences during treatment. I love finding new ways to connect my passion for writing with my interest in science, conservation and zoology.

One of the reasons I want to be a veterinarian is because I think veterinarians can and do play a crucial role in species conservation in zoos and animal sanctuaries. However, there is still a lot left to be learned about the animal species they care for.

For example, there is a species of lemur that consistently develops dental problems in captivity that lead to tooth loss, so there must be something about its diet in captivity compared to its diet in Madagascar that affects the health of its teeth. I care a lot about research concerning animals, conservation and pets, in addition to the health benefits of cathartic writing.

Victoria REALLY likes books.

I follow National Geographic on Twitter and read their articles as often as I can, but I usually end up just telling all of the cool facts I just learned to my parents, close friends or anyone else who is close enough to me to feel a slight obligation to listen and feign interest.

Through blogging, I hope to find a platform to synthesize new scientific findings surrounding animals, marine life or cathartic writing and post them to a place where people who care about and want to read about these topics can find them.

Post by Victoria Priester

Medicine, Research and HIV

Duke senior Jesse Mangold has had an interest in the intersection of medicine and research since high school. While he took electives in a program called “Science, Medicine, and Research,” it wasn’t until the summer after his first year at Duke that he got to participate in research.

As a member of the inaugural class of Huang fellows, Mangold worked in the lab of Duke assistant professor Christina Meade on the compounding effect of HIV and marijuana use on cognitive abilities like memory and learning.

The following summer, Mangold traveled to Honduras with a group of students to help with collecting data and also meeting the overwhelming need for eye care. Mangold and the other students traveled to schools, administered visual exams, and provided free glasses to the children who needed them. Additionally, the students contributed to a growing research project, and for their part, put together an award-winning poster.

Mangold’s (top right) work in Honduras helped provide countless children with the eye care they so sorely needed.

Returning to school as a junior, Mangold wanted to focus on his greatest research interest: the molecular mechanisms of human immunodeficiency virus (HIV). Mangold found a home in the Permar lab, which investigates mechanisms of mother-to-child transmission of viruses including HIV, Zika, and Cytomegalovirus (CMV).

From co-authoring a book chapter to learning laboratory techniques, he was given “the opportunity to fail, but that was important, because I would learn and come back the next week and fail a little bit less,” Mangold said.

In the absence of any treatment, mothers who are HIV positive transmit the virus to their infants only 30 to 40 percent of the time, suggesting a component of the maternal immune system that provides at least partial protection against transmission.

The immune system functions through the activity of antibodies, or proteins that bind to specific receptors on a microbe and neutralize the threat they pose. The key to an effective HIV vaccine is identifying the most common receptors on the envelope of the virus and engineering a vaccine that can interact with any one of these receptors.

This human T cell (blue) is under attack by HIV (yellow), the virus that causes AIDS. Credit: Seth Pincus, Elizabeth Fischer and Austin Athman, National Institute of Allergy and Infectious Diseases, National Institutes of Health

This human T cell (blue) is under attack by HIV (yellow), the virus that causes AIDS. Credit: Seth Pincus, Elizabeth Fischer and Austin Athman, National Institute of Allergy and Infectious Diseases, National Institutes of Health

Mangold is working with Duke postdoctoral associate Ashley Nelson, Ph.D., to understand the immune response conferred on the infants of HIV positive mothers. To do this, they are using a rhesus macaque model. In order to most closely resemble the disease path as it would progress in humans, they are using a virus called SHIV, which is engineered to have the internal structure of simian immunodeficiency virus (SIV) and the viral envelope of HIV; SHIV can thus serve to naturally infect the macaques but provide insight into antibody response that can be generalized to humans.

The study involves infecting 12 female monkeys with the virus, waiting 12 weeks for the infection to proceed, and treating the monkeys with antiretroviral therapy (ART), which is currently the most effective treatment for HIV. Following the treatment, the level of virus in the blood, or viral load, will drop to undetectable levels. After an additional 12 weeks of treatment and three doses of either a candidate HIV vaccine or a placebo, treatment will be stopped. This design is meant to mirror the gold-standard of treatment for women who are HIV-positive and pregnant.

At this point, because the treatment and vaccine are imperfect, some virus will have survived and will “rebound,” or replicate fast and repopulate the blood. The key to this research is to sequence the virus at this stage, to identify the characteristics of the surviving virus that withstood the best available treatment. This surviving virus is also what is passed from mothers on antiretroviral therapy to their infants, so understanding its properties is vital for preventing mother-to-child transmission.

As a Huang fellow, Mangold had the opportunity to present his research on the compounding effect of HIV and marijuana on cognitive function.

Mangold’s role is looking into the difference in viral diversity before treatment commences and after rebound. This research will prove fundamental in engineering better and more effective treatments.

In addition to working with HIV, Mangold will be working on a project looking into a virus that doesn’t receive the same level of attention as HIV: Cytomegalovirus. CMV is the leading congenital cause of hearing loss, and mother-to-child transmission plays an important role in the transmission of this devastating virus.

Mangold and his mentor, pediatric resident Tiziana Coppola, M.D., are authoring a paper that reviews existing literature on CMV to look for a link between the prevalence of CMV in women of child-bearing age and whether this prevalence is predictive of the number of children suffer CMV-related hearing loss. With this study, Mangold and Coppola are hoping to identify if there is a component of the maternal immune system that confers some immunity to the child, which can then be targeted for vaccine development.

After graduation, Mangold will continue his research in the Permar lab during a gap year while applying to MD/PhD programs. He hopes to continue studying at the intersection of medicine and research in the HIV vaccine field.

Post by undergraduate blogger Sarah Haurin

Post by undergraduate blogger Sarah Haurin

 

Better Butterfly Learners Take Longer to Grow Up

Emilie Snell-Rood studies butterflies to understand the factors that influence plasticity.

The ability of animals to vary their phenotypes, or physical expression of their genes, in different environments is a key element to survival in an ever-changing world.

Emilie Snell-Rood, PhD, of the University of Minnesota, is interested in why this phenomena of plasticity varies. Some animals’ phenotypes are relatively stable despite varying environmental pressures, while others display a wide range of behaviors.

Researchers have looked into how the costs of plasticity limit its variability. While many biologists expected that energetic costs should be adequate explanations for the limits to plasticity, only about 30 percent of studies that have looked for plasticity-related costs have found them.

Butterflies’ learning has provided insight into developmental plasticity.

With her model of butterflies, Snell-Rood has worked to understand why these researchers have come up with little results.

Snell-Rood hypothesized that the life history of an animal, or the timing of major developmental events like weaning, should be of vital importance in the constraints on plasticity, specifically on the type of plasticity involved in learning. Much of learning involves trial and error, which is costly – it requires time, energy, and exposure to potential predators while exploring the environment.

Additionally, behavioral flexibility requires an investment in developing brain tissue to accommodate this learning.

Because of these costs, animals that engage in this kind of learning must forgo reproduction until later in life.

To test the costs of learning, Snell-Rood used butterflies as a subject. Butterflies require developmental plasticity to explore their environments and optimize their food finding strategies. Over time, butterflies get more efficient at landing on the best host plants, using color and other visual cues to find the best food sources.

Studying butterfly families shows that families that are better learners have increased volume in the part of the brain associated with sensory integration. Furthermore, experimentally speeding up an organism’s life history leads to a decline in learning ability.

These results support a tradeoff between an organism’s developmental plasticity and life history. While this strategy is more costly in terms of investment in neural development and energy investment, it provides greater efficacy in adaptation to environment. However, further pressures from resource availability can also influence plasticity.

Looking to the butterfly model, Snell-Rood found that quality nutrition increases egg production as well as areas of the brain associated with plasticity.

Understanding factors that influence an animal’s plasticity is becoming increasingly important. Not only does it allow us to understand the role of plasticity in evolution up to this point, but it allows us to predict how organisms will adapt to novel and changing environments, especially those that are changing because of human influence. For the purposes of conservation, these predictions are vital.

By Sarah Haurin

Researcher Turns Wood Into Larger-Than-Life Insects

Duke biologist Alejandro Berrio creates larger-than-life insect sculptures. This wooden mantis was exhibited at the Art Science Gallery in Austin, Texas in 2013.

Duke biologist Alejandro Berrio creates larger-than-life insect sculptures. This wooden mantis was exhibited at the Art Science Gallery in Austin, Texas in 2013.

On a recent spring morning, biologist Alejandro Berrio took a break from running genetic analyses on a supercomputer to talk about an unusual passion: creating larger-than-life insect sculptures.

Berrio is a postdoctoral associate in professor Greg Wray’s lab at Duke. He’s also a woodcarver, having exhibited his shoebox-sized models of praying mantises, wasps, crickets and other creatures in museums and galleries in his hometown and in Austin, Texas, where his earned his Ph.D.

The Colombia-born scientist started carving wood in his early teens, when he got interested in model airplanes. He built them out of pieces of lightweight balsa wood that he bought in craft shops.

When he got to college at the University of Antioquia in Medellín, Colombia’s second-largest city, he joined an entomology lab. “One of my first introductions to science was watching insects in the lab and drawing them,” Berrio said. “One day I had an ‘aha’ moment and thought: I can make this. I can make an insect with wings the same way I used to make airplanes.”

Beetle carved by Duke biologist Alejandro Berrio.

His first carvings were of mosquitoes — the main insect in his lab — hand carved from soft balsa wood with an X-Acto knife.

Using photographs for reference, he would sketch the insects from different positions before he started carving.

He worked at his kitchen table, shaping the body from balsa wood or basswood. “I might start with a power saw to make the general form, and then with sandpaper until I started getting the shape I wanted,” Berrio said.

He used metal to join and position the segments in the legs and antennae, then set the joints in place with glue.

“People loved them,” Berrio said. “Scientists were like: Oh, I want a fly. I want a beetle. My professors were giving them to their friends. So I started making them for people and selling them.”

Soon Berrio was carving wooden fungi, dragons, turtles, a snail. “Whatever people wanted me to make,” Berrio said.

He earned just enough money to pay for his lunch, or the bus ride to school.

Duke biologist Alejandro Berrio carved this butterfly using balsa wood for the body and legs, and paper for the wings.

His pieces can take anywhere from a week to two months to complete. “This butterfly was the most time-consuming,” he said, pointing to a model with translucent veined wings.

Since moving to Durham in 2016, he has devoted less time to his hobby than he once did. “Last year I made a crab for a friend who studies crustaceans,” Berrio said. “She got married and that was my wedding gift.”

Still no apes, or finches, or prairie voles — all subjects of his current research. “But I’m planning to restart,” Berrio said. “Every time I go home to Colombia I bring back some wood, or my favorite glue, or one of my carving tools.”

Insect sculptures by Duke biologist Alejandro Berrio.

Insect sculptures by Duke biologist Alejandro Berrio.

Explore more of Berrio’s sculpture and photography at https://www.flickr.com/photos/alejoberrio/.

by Robin Smith

by Robin Smith

How A Zebrafish’s Squiggly Cartilage Transforms into a Strong Spine

A column of green cartilage cells divides into an alternating pattern of green cartilage and red vertebra

Our spines begin as a flexible column called the notochord. Over time, cells on the notochord surface divide into alternating segments that go on to form cartilage and vertebrae.

In the womb, our strong spines start as nothing more than a rope of rubbery tissue. As our bodies develop, this flexible cord, called the notochord, morphs into a column of bone and cartilage sturdy enough to hold up our heavy upper bodies.

Graduate student Susan Wopat and her colleagues in Michel Bagnat’s lab at Duke are studying the notochords of the humble zebrafish to learn how this cartilage-like rope grows into a mature spine.

In a new paper, they detail the cellular messaging that directs this transformation.

It all comes down to Notch receptors on the notochord surface, they found. Notch receptors are a special type of protein that sits astride cell membranes. When two cells touch, these Notch receptors link up, forming channels that allow messages to rapidly travel between large groups of cells.

Notch receptors divide the outer notochord cells into two alternating groups – one group is told to grow into bone, while the other is told to grow into cartilage. Over time, bone starts to form on the surface of the notochord and works its way inward, eventually forming mature vertebrae.

X-ray images of four zebrafish spines

Meddling with cellular signaling on the notochord surface caused zebrafish spines to develop deformities. The first and third image show healthy spines, and the second and fourth image show deformed spines.

When the team tinkered with the Notch signaling on the surface cells, they found that the spinal vertebrae came out deformed – too big, too small, or the wrong shape.

“These results demonstrate that the notochord plays a critical role in guiding spine development,” Wopat said. “Further investigation into these findings may help us better understand the origin of spinal defects in humans.”

Spine patterning is guided by segmentation of the notochord sheath,” Susan Wopat, Jennifer Bagwell, Kaelyn D. Sumigray, Amy L. Dickson, Leonie F. Huitema, Kenneth D. Poss, Stefan Schulte-Merker, Michel Bagnat. Cell, February 20, 2018. DOI: 10.1016/j.celrep.2018.01.084

Post by Kara Manke

Student Ingenuity vs. Environmental Issues (like Cow Farts)

Lots of creative and potentially life changing ideas filled the Fitzpatrick CIEMAS atrium last weekend. From devices meant to address critical environmental issues such as global warming and lion fish invasiveness, to apps that help you become more sustainable, Duke’s Blueprint tech ideation conference showcased some awesome, good ol’ student-led ingenuity.

These bright students from around Durham (mostly from Duke) competed in teams to create something that would positively impact the environment. The projects were judged for applicability, daringness, and feasibility, among other things. During the Project Expo, all teams briefly presented to viewers like a school science fair.

One of the projects I liked a lot was called Entropy—a website with your own personal plant (I named mine “Pete”) that grows or dies depending on your sustainable actions throughout the day. The user answers simple yes or no questions, such as, “did you turn off the lights today?”

You can also complete daily goals to get accessories like a hat or mustache for your plant. The website connects to Facebook, so you can track your friends’ progress and see how green they’re living. Ultimately it’s just a good, fun way to keep your sustainability in check. Pete was looking super-cute after I spammed the yes button.

Another interesting innovation posed a solution to the difficulty of catching lion fish. Humans are a lion fish’s only predator, and we hunt them by spear fishing. Since lion fish are highly invasive, catching them en-masse could seriously benefit the biodiversity of the ocean (plus, they taste delicious). So one team came up with a canopy like contraption that attracts lion fish to hang out underneath it, and then snatches them all up at once like a net. Pretty neat idea, and if it was implemented on a large scale could be a huge benefit to the Earth’s oceans (and restaurants)!

After the expo, the top seven teams were selected and given three minutes to present to the judges and audience as a whole.

Every project was astounding. “Collide-o-scope” came up with a simple Arduino-based device to transmit elephant seismic activity to train drivers nearby in order to reduce the number of train-elephant collisions in India and Sri Lanka — currently a huge problem, for both us as humans and the elephant population.

Another team, “Manatee Marker,” proposed a system of solar powered buoys to detect manatees, with the hope of reducing frequent manatee-boat accidents. Considering that manatees are quiet, basically camouflaged, and thermally invisible, this was quite an ingenious task.

Perhaps my favorite project, “Algenie” stole the show. Methane gas is a huge factor to global warming — around twenty-five times more potent as a heat-trapping gas than Carbon Dioxide — and a lot of it comes from cow farts. However, we’ve recently discovered that putting seaweed in cow feed actually lowers methane emissions almost entirely! So this team came up with a vertical, three-dimensional way to grow algae — opposed to “two-dimensionally” growing across a pond — that would maximize production. Global warming is obviously a massive issue right now and Algenie is looking to change that. They ended up getting first place, and winning a prize of $1,000 along with GoPros for every team member.

Algenie’s prototype

At the end of the day, it wasn’t about the prize money. The competition was meant to generate creative and practical ideas, while promoting making a difference. After  attending the expo I felt more aware of all the environmental issues and influenced to help out. Even if you don’t feel like spending the time drafting up a crazy buoy manatee-detecting system, you can still do your part by living sustainably day to day.

Blueprint has done an awesome job of spurring young, enthusiastic students towards helping this planet — one cow fart at a time.

Post by Will Sheehan; Will SheehanPictures from Duke Conservation Tech

How A Bat’s Brain Navigates

Most of what we know about how the hippocampus, a region of the brain associated with memory formation and spatial representations, comes from research done on rodents. Rat brains have taught us a lot, but researchers in Israel have found an interesting alternative model to understanding how the hippocampus helps mammals navigate: Bats.

The Egyptian fruit bat proved the perfect subject for studies of mammalian navigation.

Weizmann Institute neurophysiologist Nachum Ulanovsky, PhD, and his team have looked to bats to understand the nuances of navigation through space. While previous research has identified specific cells in the hippocampus, called place cells, that are active when an animal is located in a specific place, there is not much literature describing how animals actually navigate from point A to point B.

Nachum Ulanovsky

Ulanovsky believes that bats are an ingenious model to study mammalian navigation. While bats have the same types of hippocampal neurons found in rats, the patterns of bats’ neurons’ firings more closely match that of humans than rats do.

Ulanovsky sought to test how bats know where they are going. Using GPS tracking equipment, his team found that wild bats that lived in a cave would travel up to 20 kilometers to forage fruit from specific trees. Night after night, these bats followed similar routes past perfectly viable food sources to the same tree over and over again.

The understanding of hippocampal place cells firing at specific locations doesn’t explain the apparent guided travel of the bat night after night, and other explanations like olfactory input do not explain why the bats fly over good food sources to their preferred tree.

The researchers designed an experiment to test how bats encode the 3D information necessary for this navigation. By letting the bats fly around and recording brain activity, Ulanovsky and team found that their 3D models are actually spherical in shape. They also found another type of hippocampal cells that encode the orientation the bat is facing. These head direction cells operate in a coordinate system that allows for a continuity of awareness of its orientation as the animal moves through space.

http://www.cell.com/cms/attachment/2091916945/2076305003/gr1_lrg.jpg

Ulanovsky found bats relied on memory to navigate toward the goal.

To understand how the bats navigate toward a specific goal, the researchers devised another experiment. They constructed a goal with a landing place and a food incentive. The bat would learn where the goal was and find it. In order to test whether the bats’ ability to find the goal was memory-based, or utilized the hippocampus, the researchers then conducted trials where the goal was hidden from the bats’ view.

To test whether the bats’ relied on memory, the Ulvanosky team measured the goal direction angle, or the angle between the bat’s head orientation and the goal. After being familiarized with the location of the goal, the bats tended toward a goal-direction angle of zero, meaning they oriented themselves toward the goal even when the goal was out of sight.

Continued research identified cells that encode information about the distance the bat is from the goal, the final piece allowing bats to navigate to a goal successfully. These hippocampal cells selectively fire when the bat is within specific distances of the goal, allowing for an awareness of location over distance.

While Ulanovsky and his team have met incredible success in identifying new types of cells as well as new functions of known cells in the hippocampus, further research in a more natural setting is required.

“If we study only under these very controlled and sterile environments, we may miss the very thing we are trying to understand, which is behavior,” Ulanovsky concluded.

By Sarah Haurin

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