Seeing may not be perceiving—the neurobiology of perception

The elephant-nosed electric fish

The elephant-nosed electric fish

By Olivia Zhu

Larry Abbott argues that sensation is not perception. In a lecture presented on March 25th to the Department of Neurobiology at Duke, Dr. Abbott, of the Center for Neurobiology and Behavior at Columbia University, presented his model of integrated perception.

Dr. Abbott went into particular depth about how an organism can tell itself apart from its surroundings. Though we may take it for granted, self-identification is extremely important in many instances: for example, when a young, male zebra finch learns how to sing by copying his tutor, he must be able to distinguish his own song from other birds’ songs in order to properly listen to it and refine it.

Dr. Abbott studies self-perception in elephant-nosed electric fish. Electric fish have an organ in their body that sends out strong electric pulses. However, the fish also have a sensory organ to detect electric pulses from potential prey, which are several orders of magnitude lower than their own signals. Their own electric fields should diminish their sensitivity to external electricity; this interference, though, is prevented because their electricity-generating organ sends impulses to the sensory organ to inform it when it is firing. Essentially, the fishes’ neural circuits are tuned to cancel out the input they receive from their own electric pulses.

Ultimately, Dr. Abbott claimed that when you look at your friend, you’re not exactly seeing your friend: your mental image is a product of various mental manipulations of the original sensory input your brain receives. His mathematical, model-based approach attempts to redefine the way in which we view ourselves and our relation to the world.

Why are Dogs Skinny in Costa Rica?

By: Nonie Arora

Duke student Mary Chavarria had the opportunity to learn how animals are treated in an indigenous community in Costa Rica. Chavarria is a junior from Los Angeles, California studying evolutionary anthropology. An avid traveler, she is a also a member of Round Table and on the executive broad of the Duke Undergraduate Bioethics Society.

Chavarria and her group members presenting their findings. Credit: Mary Chavarria

Chavarria and her group members presenting their findings. Credit: Mary Chavarria

Last semester, she studied abroad in Costa Rica through the Duke OTS program on tropical medicine & global health. In addition to taking classes on tropical medicine and field ethnobiology, Chavarria had the opportunity to complete a research project while in the region.

The minister of health for the region presented the students with potential topics that he believed ought to be investigated for the indigenous communities. There was a range of projects: dental health, isolated older adults, social groups and pets. Chavarria and her group chose to research how pets were perceived and the health of pets in the community.

Her group wanted to know how perceptions of animals influence their health as pets and how this would correlate with zoonosis, the transfer of disease from animals to humans. To determine perceptions of animals, they developed a survey to use in a school.

“We knew that it would be difficult to just go house to house. We would have to hike between them and there are mountains in between. We decided that the best way to access most people reliably would be to go to a school,” Chavarria explained.

They asked questions like:

  • Do you like your pet?
  • Do you play with it?
  • Why do you have a pet?
The team meets with students to ask them about pets. Credit: Mary Chavarria

The team meets with students to ask them about pets. Credit: Mary Chavarria

They surveyed 70 kids from elementary and middle school. Their response rate was almost one hundred percent since they administered the survey in classrooms.

“We found that pets were not treated as you or I may consider [treating a pet]: groomed or walked. They were utilitarian, to put it gently. The pets were skinny,” Chavarria explained.

“While the animals were skinny, people also don’t have great nutrition in this under-resourced region. People would feed them parts of what they were eating, which wasn’t supremely nutritious for humans, and [was] even less so for dogs,” Chavarria said.

Chavarria’s team also found that people in the region really didn’t know the extent to which diseases could be transmitted between humans and animals. Scabies, spread by a parasite that causes similar diseases in humans and dogs, is a problem in the region, she added.

Ultimately, Chavarria believes that better awareness of disease transmission between animals and humans and better treatment of animals has the potential to reduce human disease.

New Fossil Cache Hints at Human Ancestry

By Erin Weeks

In October 2013, three South African cavers made a discovery that may change our understanding of human origins.

Just 25 miles outside Johannesburg lies the Cradle of Humankind, a World Heritage Site marked by limestone caves, in which decades of research have unearthed an abundance of early hominin remains. Five years ago, the caves yielded a new species, Australopithecus sediba, whose classification has divided the anthropology community. And as recent months have shown, the Cradle of Humankind holds many more secrets.

At the bottom of one cave complex, past a fissure just eight inches wide, the cavers discovered what looked like hominin fossils lying undisturbed in soft dirt. The findings triggered a frenzy of activity, as researchers scrambled to assemble a team to investigate the promising fossils. One member was Duke paleoanthropologist Steve Churchill, who discussed his work on A. sediba and the new, as-of-yet unclassified fossils last week in a lecture on campus called “The 2-Million-Year-Old Boy.”

The research tents at the Rising Sun excavation site in South Africa (Photo: Steve Churchill)

The research tents at the Rising Sun excavation site in South Africa (Photo: Steve Churchill)

The National Geographic Society provided emergency funding for a three-week endeavor dubbed the Rising Star Expedition, which has been chronicled online by scientist Lee Berger (the blog has great pictures of the caves and fossils).

In those marathon three weeks, the team catalogued 1,200 fossils. By comparison, Churchill explained, 65 years of excavation yielded just 400 and 500 hominin fossils, respectively, in two nearby sites.

At first, the team hoped they might have a full skeleton from one individual on their hands–but as the expedition progressed, they realized that the fossils came from 12 to 20 different individuals.

Perhaps most fascinating is what researchers haven’t found at Rising Star: other animals. At most sites in the Cradle of Humankind, hominin knucklebones and teeth are scattered indiscriminately among antelope and leopard fossils. Researchers may never know why so many primates, yet nothing else, were preserved in Rising Star’s remote chambers, but it’s clear the assemblage formed under conditions very different than those of the nearby cave sites.

A peek inside the science tent. All of the equipment for the three-week expedition had to be hauled out to the cave site. (Photo: Steve Churchill)

A peek inside the science tent. All of the equipment for the three-week expedition had to be hauled out to the cave site. (Photo: Steve Churchill)

Where these primates belong on the hominid family tree is another lightning-rod question the team is working to answer. The age of the fossils is currently unknown, but there are indications they may fall into the time range in which early members of the genus Homo were first beginning to arise. If so, they may help to upend current theory, which holds that our Homo forebears evolved in East Africa rather than present-day South Africa.

Whatever the final word on their taxonomy, it’s clear the Rising Star fossils will lead to anthropological insights for years to come.

Finding Order in Insect and Orc Swarms

Ouellette's model of insect swarming

Ouellette’s model of insect swarming

By Olivia Zhu

Dr. Nicholas Ouellette looks for the organization in disorder.

Ouellette, associate professor in the mechanical engineering department at Yale University, studies collective motion in animal systems. On February 17, he presented his models of swarming of Chironomus riparius, the non-biting midge, as part of Duke’s Physics Colloquium. Ouellette ultimately hopes to pin down fundamental laws of biology through his physics research.

In the lab, Ouellette has found that Chironomus insects swarm in a columnar, teardrop shape in the center of their container. They only live in their flying state for two to three days, during which they mate, lay eggs and die. During this period, swarming affords them protection from predators and the opportunity to mate.

Ouellette and his lab have devised various methods of modeling the insects’ swarming. They found that the insect density remains constant, and that the “scattering,” or collisions of insects, mirrors that of an ideal gas over long periods of time. Interestingly, the graph of individual insect speed follows a Maxwell-Boltzmann distribution, even though the lab did not track the usual factors that create such a distribution, like temperature.

The most pressing question Ouellette would like to answer is which factors create a swarm—he has determined that close insect-insect repulsion contributes to swarming, but distant insect-insect attraction does not. To pursue this question, Ouellette is testing how many insects it takes to make a swarm.

Wildebeest stampede modeled in The Lion King

Wildebeest stampede modeled in The Lion King

Other animals that exhibit collective motion are mackerel, wildebeests and starlings. Some familiar examples of collective motion modeling are visible as the Orcs storm the castle in Lord of the Rings and as the wildebeests charge the canyon in The Lion King.

Four Things You May Not Know about Ecologist E.O. Wilson

By Erin Weeks

Edward O Wilson Red Hills, Aalabama  2010 by Beth Maynor Young 6x9_0

(Photo: Beth Maynor Young)

Edward O. Wilson is one of the most renowned living biologists, the world’s foremost authority on ants, and for a little while at least, a member of the Duke faculty.

Wilson is on campus teaching the first of an annual course, part of a recent partnership between the E.O. Wilson Biodiversity Foundation and Duke’s Nicholas School of the Environment. Feb. 11, he spoke to a sold-out auditorium about “The Diversity of Life,” a lecture that was equal parts awe-inspiring facts, humorous anecdotes from a life in science and call to arms for future generations.

Here are four things the audience learned last night about E.O. Wilson.

1. He’s dabbled in dreams of Jurassic Park. When asked what he thought of de-extinction, the plan to resurrect vanished species using their DNA, Wilson enumerated all the reasons why the efforts may be futile: we have only genetic shreds; the appropriate habitat may be gone; we can’t produce breeding populations from limited DNA.

But then he paused. “I’ll tell you frankly,” he said, “I’d like to see a mammoth.”

2. He made his first scientific discovery as an adolescent. An eye permanently damaged in a fishing accident led the young Wilson to his interest in ants, which he could view up close. One day in his native Alabama, he discovered a ferocious mound-building species he’d never seen before. He didn’t recognize it then, but those were among the first of the destructive red fire ants that would soon invade the entire Southeast, causing billions of dollars of economic and medical damage.

3. The man is 84 and still going strong. Professor Wilson closed his talk with a passage from his newest book, arriving in April, called “A Window on Eternity: A Biologist’s Walk Through Gorongosa National Park.” He’s written two dozen other books, including a foray into fiction at age 80 (the novel, called Anthill, won him the 2010 Heartland Prize for fiction).

4. The future is in nematodes. Or fungi. Or Archaea. Throughout the talk, Wilson reiterated his hopes for young scientists to become the cataloguers and guardians of Earth’s immense biological diversity. Only a fraction of the planet’s estimated species of nematodes, fungi and Archaea are known to science, and “these little things run the world,” he said.

The need for “-ologists” has never been greater, he said.

(Photo: Jared Lazarus)

(Photo: Jared Lazarus)

VIEW THE ENTIRE TALK (YouTube, 1:10 with introductions)

Inside the Monkey Brain

By Ashley Mooney

Both in the lab and on a tropical island, primate behaviors can shed light on social-decision making.

To fully understand the biology of social-decision making, Michael Platt, director of the Duke Institute for Brain Science, conducts lab work at Duke and field research an island off the coast of Puerto Rico called Cayo Santiago. His research focuses on understanding both the physiological and social aspects of decision making.

“Our brains are exquisitely tuned to making [social] decisions and acquiring the information to inform them,” Platt said. “When these processes go awry, as occurs in disorders like autism, schizophrenia or anxiety disorders, the consequences can be devastating.”

Courtesy of Lauren Brent.

Courtesy of Lauren Brent.

Platt’s group uses rhesus macaques as model animals because of their strong behavioral, physiological and neurobiological similarity to humans. But understanding how the monkey brain—and thus the human brain—works requires both laboratory-based biological information and social studies in a natural environment.

Researchers can combine the knowledge they gain from lab and field studies to create a holistic picture of the biological basis of behavior, said Lauren Brent, associate research fellow at the University of Exeter who did her post-doc with Platt at Duke.

Lab studies are best suited for quantitative, repeatable studies in which variables can be precisely controlled, Platt said. On the other hand, field studies emphasize external validity and an animal’s response in its natural conditions, but are not suitable for determining precise measurements of internal processes.

In the lab, Platt’s group studies the neural mechanisms that mediate prosocial and antisocial decisions, Platt said. They can also study the ways in which humans can enhance prosocial decisions using pharmacological or behavioral interventions.

On Cayo, the researchers are exploring the genetic factors that shape individual differences in social behavior and decision-making in free-living monkeys. They use observations, behavioral experiments and blood and fecal samples to study the monkeys non-invasively.

“The project on Cayo and the work that goes on the lab are complementary in the best sense because we can do things on Cayo that we can’t do in the lab,” Brent said. “For example, we have hundreds of monkeys, of known pedigree, interacting with each other in a purely spontaneous and naturalistic fashion. You can’t get that in a lab.”

Lauren Brent conducting behavioral observations on Cayo. Courtesy of Lauren Brent.

Lauren Brent conducting behavioral observations on Cayo. Courtesy of Lauren Brent.

Although working with free-ranging monkeys can produce more naturalistic results, Brent noted that there are drawbacks to working in the field.

“Working with monkeys in the field is painstaking,” Brent said. “You need to be physically fit, but moreover it is a mentally demanding thing to do because you need to pay close attention to everything that is going on in the group at all times so that the data are as finely detailed and accurate as possible.”

Brent found that a monkey’s position in its social network is heritable and can impact the survival of its infants. She determined a monkey’s social connections using grooming and spatial proximity, or how long one monkey spends sitting next to other monkeys.

“Regardless of how big your family is, monkeys who are better connected in the grooming network have greater reproductive success,” Brent said. “Together, these results suggest that social interactions have adaptive benefits and are something on which selection has acted.”