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FALL 2011
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Feature

On Our Be(a)st Behavior

Why do we need sleep? How do we control movement? How could societies be more cooperative? Researchers in the Department of Neurobiology and Behavior are gaining remarkable insights into these questions and more through their study of our fellow animals.

By Stacey Shackford

Zebrafish
Credit: Jay Patel and Tom Hawkins, University College of London

Zebrafish: Dorsal view of the zebrafish brain showing axons and neuropil

What can a simple, sinewy four-millimeter-long fish larva possibly tell us about complex conditions like Parkinson’s disease? How about the humble honeybee—and politics? Or the cacophonous cricket —and courtship.

Plenty.

From basic biology to befuddling behavior, it turns out there’s an awful lot we can learn from our fellow animals, if only we know where to look.

Scientists in the Department of Neurobiology and Behavior (NBB) peer into the spines of zebrafish, hover over the hives of honeybees, and venture into the wild to watch other animals in their natural habitats.

Their discoveries have shed light on the way we walk, talk, and walk the talk. And their unique collaborations have helped transform the field, which is one reason why their classes are consistently full of curious undergraduates. Around 250 choose it as their focus, making NBB the most popular concentration among biology majors.

Neurobiology and behavior is a synthesis of many disciplines: physiology and anatomy, ecology, vertebrate and invertebrate zoology, biological psychology and anthropology, genetics, developmental biology, chemistry and biochemistry, physics, and mathematics. The interests of the department’s 23 faculty members and 29 graduate students span a broad spectrum. Some study how behavior works on the neurological level, others how it evolves. The common glue is a shared interest in what animals do—and what that might mean for humans, who are animals too.

Cypripedium acaule
Credit: Kent Loeffler

Pollinating a flower can be a daunting task for bees and other insects. Luckily, the plants often offer some tactile and olfactory chemical assistance.

FishFish talk
From hoots and grunts to cringe-inducing cries, it turns out that fish and humans have a lot in common when it comes to communication. Like other vertebrates, fish vocalize to communicate important information—such as health and reproductive status—to potential mates and neighbors. In the case of the toadfish, they use their “swim bladders,” air-filled sacs that allow fish to alter their buoyancy. By vibrating nearby muscles, the sacs also become sonic instruments. Boris Chagnaud—a postdoctoral researcher in Professor Andrew Bass’s lab who is now at the University of Munich—identified two distinct groups of neurons that control the duration and frequency of such vocalizations. The finding could provide a road map for understanding how our own brains build neural codes to control our larynx, and how birds control their syrinx, Bass says.

BirdDon’t call me Polly
They’re talkative birds, with impressive, humanlike linguistic abilities, and thanks to graduate student Karl Berg, we now know that parrots learn their first calls just as human infants do—from their parents. Berg ventured to Venezuela to study green-rumped parrotlets and found that the birds make signature contact calls, sounds that function much like a name, that are used to find and recognize mates and identify chicks. He swapped eggs around to see if the chicks would pick up calls resembling those of their foster parents or their biological ones. He found the foster parents were their role models.

MouseRun, mouse, run
When you’re being chased by a hawk, you’re better off scampering than galloping, even though galloping is faster—dexterity wins over speed. That’s just one lesson Professor Ronald Harris-Warrick learned by studying the way mice run. He identified a group of spinal cord nerve cells responsible for locomotion in the animals and studied how they worked at different speeds to maintain a normal running pattern and prevent the switch to galloping at high speed. It’s the first such research to examine the mouse spinal cord at more than a single locomotion speed, and it involved various methods, including meticulously inserting microscopic electrodes into single nerve cells and electrically stimulating nerves to simulate signals from the brain.

Bird

Avian divorce
Bird families have more structural parallels to human families than most primates, according to Emeritus Professor Stephen Emlen, who has spent 25 years observing avian species that engage in bi-parental care and cooperative breeding. When a stable pair bond is broken (through death or separation), and a new replacement pair bond is formed, it often leads to increased conflict among family members. These changes closely parallel changes reported after divorce and remarriage in human families. Predicting these changes in birds has implications for understanding stepfamily dynamics, Emlen says. Family counselors have taken note, incorporating many of his theories into their practices.

FlyThe flies have it
Some species of flies have ears that are smaller than the head of a pin yet can localize sounds as well as ours can. Studies by Professor Ronald Hoy into how they solve problems of acoustical physics have led to collaborations with engineers to design a new generation of hearing aid microphones that “biomimic” fly ears. Fruitflies have also proven a good model to study epilepsy, as they suffer from seizures similar to humans. Associate Professor David Deitcher uses the insects to help identify the pathways that regulate the relevant neuron activity. A group of undergraduates affiliated with the nonprofit student group FACES (Facts, Advocacy, and Control of Epileptic Seizures) also operate their own lab, in which they study the effects of epileptic drugs on the flies.

Rules of Attraction

Imagine visiting a flower as a bee. It would be a lot like entering a big, bright bouncy castle with a ball pit in the center, sensory overload giving way to confusion as you try to locate a single straw hidden in the dark depths in search of a few mouthfuls of sweet, sustaining sugar water—while also expending a lot of energy hovering and manipulating your bulbous body into strange configurations. You’d probably appreciate a few tactile or olfactory cues.

Luckily, plants provide such assistance, often through complex chemical processes that have only recently been unraveled – by NBB professor Rob Raguso and a few others worldwide – through the field of chemical ecology. Founded by Raguso’s predecessor, Professor Thomas Eisner (see sidebar), chemical ecology is the study of chemicals involved in the interaction of organisms such as insects and plants.

Traditionally, it’s been the bold colors and shapes of flowers that have attracted the attention of ecologists, and the assumption was that those were also the most important characteristics for insects.

But Raguso has found that this is not always the case. So much else has to be considered: scent, flavor, location, environment, population, and timing.

“All the bright displays and odor in the world may not convince insects to pollinate,” Raguso says. “They interpret their world through environmental cues and context.”

Raguso, who joined the department in 2007, has done groundbreaking work in understanding odors. For instance, he discovered that strawberry pollen has an attractive scent, that the same odors dissolved in the nectar of sky pilot flowers can be used to simultaneously attract pollinators and repel enemies, and that some plants communicate with their preferred pollinators through a “secret handshake” of chemicals.

A discovery that tobacco hornworm moths have carbon dioxide receptors on their lips led him to explore what role the compound might play in pollination. He found that the large flowers let out a big breath of CO2 when they exploded open at night.

Although the flowers remained open and visually attractive all night, the moths were more likely to visit when the presence of CO2 was strongest, perhaps because it indicated the flower was newly opened and thus more likely to contain nectar.

“That was a riveting discovery. It’s something really basic and it makes sense to everybody in retrospect, but no one had thought to look for it,” Raguso says.

Raguso’s work has some very practical implications for humans. Understanding why insects are attracted to certain colors and odors could lead to the development of more effective traps, transforming pest management practices. And his research sheds a lot of light in other applied industries where chemistry matters, such as wine. 

Moving Testimonies

Two floors down, on the ground floor of Corson-Mudd, Professor Joseph Fetcho spends his days surrounded by fish, something he didn’t imagine he’d be doing 10 years ago. He started out as a snake person. But he’s grown quite fond of the tiny swimmers whose transparent bodies enable him to directly observe their inner workings.

A fully sequenced and easily manipulated genetic system adds to the attraction, as does the availability of “brainbow” gene technology that allows for the creation of color-coded nervous systems and dynamic mapping of changing neural activity in live animals.

Thanks to the humble fish – and Fetcho’s visionary observations - we now know a great deal more than we once did about how the nervous system produces and controls movement.

We know that our circuits are built in a highly organized, temporal order, for example.

This has potential implications for Parkinson’s disease, which is characterized by a slowing of movement. Fast movements seem to be the first to go; those are also the first ones the body produces, the “oldest” in the system, according to Fetcho’s research, so there may be some correlations.

“If you don’t understand how speed of movement works, it’s very difficult to begin to understand what happens in Parkinson’s disease,” Fetcho says. “We hadn’t even thought to look until we saw this pattern in age-related order tied to function in zebrafish.”

The small fish are also helping Fetcho unlock clues about what happens in the brain while we sleep – and why we sleep at all.

“One of the biggest questions in neurobiology is why we need sleep, which you’d think we would have answered by now,” says Fetcho.

“Animals that are deprived of sleep die. Something fundamental is going wrong with their nervous system function, yet we still don’t know what that is.”

By observing changes in neural activity at different times of the day, in different states of sleep, Fetcho hopes that zebrafish will once again provide critical answers to this fundamental, universal question.

“I think to some extent society is losing sight of the relevance of all animals for human biology. It’s very important to appreciate that we can learn a lot about human biology by studying non-human animals,” states Fetcho.

Cooperative Attention

Fetcho’s colleague Professor Thomas Seeley doesn’t just consider himself a scientist; he’s a “social physiologist.” His subject: bees.

“The hive is an exquisite piece of biomachinery that runs as smoothly as our bodies,” Seeley says. “It’s like a superorganism, with all of the bees cooperating and working together to make a functioning whole.”

“I want to understand how they work so well to solve problems, such as controlling internal temperatures, gathering enough nutrient-rich food, deciding when to expand the nest, and where to live when setting up a new home. These are all questions we face ourselves as organisms, but bees have to do it together, as a society,” he adds.

An example of this is outlined in his bestselling book, Honeybee Democracy. When bees relocate to a new home, they leave the hive in a swarm of some 10,000 bees. The vast majority of them rest quietly in a beard-like cluster that hangs from a tree branch, while about 500 fly off to scout out potential dwelling places.

When they return, each tries to sell her discovery through a series of signals that form a “waggle dance.” The bees then select the winning site together by conducting a popularity contest – much like our own political process, Seeley says. “The one difference is that the bees are completely honest, and to the best of our knowledge they don’t resort to negative campaigning.”

Honeybees have good reason to be so harmonious: everyone’s working towards the same reproductive goal, with a single queen bee generating all the offspring, and the worker bees acting as policemen, eating any errant eggs laid by common workers.

That’s not the case for wasps, says Professor Hudson Kern Reeve, Ph.D. ‘91. Their nests often contain more than one female. Some are more dominant than others, and they seem to exercise this dominance at different levels. If they sense one of the subordinate females may leave the colony and venture out to set up her own competing nest, for instance, they may cede some of their reproductive control in order to entice her to stay.

“The workers have lots of incentives for being selfish in a wasp society, and that’s why I’m interested in them. How do they balance the degree of selfishness and cooperation within these societies?” Reeve says.

It can create conflict, but not always. There’s often a tug-of-war between individual and group needs, and it seems to be driven by competition. Internal competition is often overcome by the need to band together to stave off external competition. Introduce a new
neighboring colony, and suddenly production and cooperation skyrocket, Reeve has found. Sound familiar?

One of Reeve’s students, Jessica Barker, tested this tug-of-war theory on Cornell undergraduates. She handed $100 to the students and gave them the option to either keep the entire sum or contribute it to a pot whose contents would be multiplied by some factor and then divided equally among the group’s members. The majority contributed to the pot. When an element of competition was added – participants were told they could pay for increased shares – cooperation dropped, and was only restored when they were reassured there would be no cheating.

Reeve believes many similarities can be drawn between insect and human societies, especially when it comes to cooperation and conflict.

“They’re not just small-brained robots with wings. They’re making sophisticated social decisions from moment to moment,” he says. “The same principles might also apply on the molecular level, within cells and genomes.

“Can we explain the variation of conflicts in a way that will enable us to minimize conflict in human groups and ultimately design more cooperative societies? That’s my long-range goal, but we are not going to do it right unless we understand the underlying behavior based on sound evolutionary principles,” Reeve adds.

Singing Clues

Kimberly McArthur
Credit: Kent Loeffler

Post doctoral associate Kimberly McArthur, above, takes a close-up look at a zebrafish in Professor Joe Fetcho's lab.

tanks of zebrafish
Credit: Kent Loeffler

Technician Nicole Gilbert, left, tends to the hundreds of tanks of zebrafish in the basement of Mudd Hall.

Professor Kerry Shaw is also interested in evolutionary principles, particularly what drives new species to form.

She observes crickets, and in particular, closely related cricket species in the genus Laupala endemic to Hawaii – an ideal place to study evolution in action because the Big Island is a contained geographic area with a well-documented and visible geologic history that goes back just 500,000 years.

Environmental adaptation does not explain the speciation of crickets on the islands, but changes propelled by sexual selection might.

The male crickets Shaw studies produce a simple song, and the females are very attuned to variations in that song, with a remarkable ability to distinguish pulse rates between different species.

Fortunately, those simple songs are also pretty simple to synthesize on a computer. Placed on a table between two speakers, a female cricket will walk toward the source of sound she finds most appealing, making it easy to measure her preferences as researchers introduce different songs.

Shaw suspects some of those preferences may be genetically driven. Much is unknown about cricket genetics, but Shaw has been able to map the genes believed to be connected to the crickets’ communications and has found that the simple songs are actually controlled by a complex assortment of genes. These genes seem to be located in the same region of the genome, in both the male and female, which suggests that which drives the call also drives the response.

“If those genes are linked, it’s easy to imagine how changes in one trait could lead to changes in mating,” Shaw says.

As the signals and preferences among different groups of crickets change, they become less likely to breed outside their groups, and the gene flow between them declines until it becomes completely severed, and separate species emerge.

“Although we don’t completely understand the reasons, we can see the consequences,” she says.

In addition to studying cricket behavior, Shaw also does research into the basic biology of her subject.

“Understanding how species exist in the world is a fundamentally important question that enriches our experience,” she explains. “Where would we be if we didn’t have a knowledge of biodiversity? I think we would be much poorer.”

Inspiring Behavior

Corson-Mudd Hall is one of the only places in the world where you can find such breadth of behavioral research.

“We are pretty special,” Seeley says. “Most programs have neurobiology in one department, and behavior tucked elsewhere, such as ecology and evolutionary biology.

“We envisioned in the 1960s that neurobiology and behavior were converging, and that proved correct,” he adds. “Traditionally, the field has been interested in investigating the activities of individual neurons, on a cellular basis. The hot area now is in the circuitry that underlies behavior, how the nervous system processes emotions or handles decision-making. The field has kind of caught up to us.”

Raguso definitely sees the benefit in being constantly challenged to think beyond the science and consider it in context of behavior, adaptation, and evolution.

Fetcho agrees. He believes context is everything. When confronted with a fever, for instance, your instinct is to try to attack and alleviate it; but you may reconsider when you realize why the fever evolved – as a means for the body to kill bacteria.

“We must keep in mind these functional roles,” Fetcho says. “Having people who think about what the behavior means for the organism in its environment helps us understand the neurobiology.”

It’s also led to some unexpected collaborations.

When Fetcho noticed a correlation between IQ and the ability to tap out a consistent, measured metronome rhythm, he suspected it might have something to do with good neural wiring and body control.

He shared his hypothesis with Reeve, who wondered whether there was further correlation among animal calls and the timing efficiency of their nervous systems, theorizing that the steadier songs would be more attractive because they suggested the creature would also have other favorable neural-controlled characteristics, such as quick reaction times.

They then turned to Shaw, who used her crickets to test the theory. Early results seem to support their hypothesis, and the trio plan to continue the collaboration.


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