Monday, April 5, 2010

RODEO BULL GOES HEAD-TO-HEAD WITH ZOO DOLPHINS IN A STUDY OF BALANCE

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Dolphins, whales and porpoises have extraordinarily small balance organs, and scientists have long wondered why.

Now a study at Washington University School of Medicine in St. Louis has contradicted a leading theory, which held that the animals moved their heads so vigorously that they had to have smaller, less responsive balance organs to avoid overwhelming their senses.

Working with a Midwestern zoo and a local rancher, the researchers, led by Timothy E. Hullar, MD, a Washington University ear, nose and throat specialist at Barnes-Jewish and St. Louis Children's hospitals, directly measured the head movements of dolphins and compared them with those of a closely related land animal — a rodeo bull. Cattle have much larger balance organs than dolphins, yet the tests showed that both species had similar head motions.

The findings will be published in the April issue of the Journal of Experimental Biology. Hullar says the results deepen our understanding of the role of balance systems, including those of people.

Much of an animal's or person's balance is controlled by the semicircular canals located in the inner ear. Even though a bottlenose dolphin is about 8 feet long, its semicircular canals are as tiny as those of the average mouse, an animal that could comfortably ride on the tip of the dolphin's nose.

"About 35 million years ago, the ancestors of whales and dolphins went from a terrestrial habitat to an aquatic habitat," says Hullar, assistant professor of otolaryngology and of anatomy and neurobiology. "During this evolutionary process, their semicircular canals got smaller and smaller. The scientific thinking has been that since the canals measure head motion, something must have changed a lot in how these animals move their heads."

Hullar points out that the general trend is for vertebrate semicircular canals to be proportional to body size. Since dolphin canals are so much smaller than the rule suggests they should be, perhaps, scientists thought, dolphins move so much that a large balance organ would be too sensitive to work properly.

Dolphin trainers at the Indianapolis Zoo agreed to work with Hullar and Benjamin M. Kandel, a Yeshiva University undergraduate student conducting summer research in Hullar's lab, to measure dolphin head movement to test this hypothesis.

"They were glad to help because zoo dolphins aren't there just to entertain but also to help educate us about the species," says Hullar, who is also on the faculty of the Program in Audiology and Communication Sciences of the Central Institute for the Deaf at Washington University School of Medicine. "They trained their dolphins to carry in their mouths a plastic pipe that contained a gyroscope and recording device so we could precisely measure their motion. Our study is the first to directly measure the head motion of dolphins."

Next, the researchers had to find a land animal to match the dolphins. Two-toed animals such as pigs, camels and hippopotamuses are closely related to dolphins. So are cattle. So when one of Hullar's patients turned out to be a rancher, Hullar asked him if he had any bulls he could work with. He didn't, but he put Hullar in touch with a neighbor who raised bulls for the rodeo circuit.

"I called him, and he said 'come on down' and directed me to his ranch in southeastern Missouri — part of the directions included making a left turn at the second chicken house," Hullar says. "He and his assistants duct-taped the gyroscope to the bull's horns and let him into the ring."

As the bull bucked and trotted around the ring, the device recorded its head movements. When the researchers went back to the lab and analyzed their data, they found the speed of the bull's head motions while trotting was remarkably similar to that of the dolphins' while swimming. The speed of the bull's head motions during bucking was like the dolphins' when they spun in the water.

"A few years ago, our lab was the first to record the nerve signals in mouse balance systems, and we showed that the smaller an animal's semicircular canal, the less sensitive it is," Hullar says. "Smaller canals, such as dolphins', would provide the animal with less information about motion. A dolphin's head is certainly large enough to hold a larger balance system, and because we've found their small canals aren't related to head motion, the question as to why they are so small remains open."

Hullar will continue to try to answer this question by looking at the nerves that are linked to balance systems to see if the explanation lies in some aspect of nerve transmission or brain processing. In addition, he is working to build experimental models of semicircular canals using computer programs so he can test the effect of various movements on their function.

(Photo: WUSTL)

Washington University School of Medicine

TRAUMATIC BRAIN INJURY CAUSES LOSS OF SMELL AND TASTE

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The ability to taste and smell can be lost or impaired after a head injury, according to a new study by scientists from the Université de Montréal, the Lucie Bruneau Rehabilitation Centre, as well as the Center for Interdisciplinary Research in Rehabilitation of Greater Montreal. Published in the journal Brain Injury, the investigation established that mild to severe traumatic brain injury could cause olfactory loss.

"The study clearly demonstrates that olfactory deficits can occur in mild traumatic brain injury patients as well as in moderate and severe TBI patients," says study co-author and neuropsychologist Maurice Ptito, a professor at the Université de Montréal School of Optometry. "We also found that patients with a frontal lesion were more likely to show olfactory dysfunctions."

The research team recruited 49 people with TBI (73 percent male with a median age of 43) who completed a questionnaire and underwent two smell tests to measure their olfactory loss. The result: 55 percent of subjects had an impaired sense of smell, while 41 percent of participants were unaware of their olfactory deficit.

"Both tests indicated the same results: patients with frontal injury are more likely to suffer olfactory loss," says lead author Audrey Fortin, a professor at the Université de Montréal School of Optometry and researcher at the Lucie Bruneau Rehabilitation Centre.

Smell plays a vital role in our lives, says Dr. Fortin, since olfaction influences what we eat, can help us detect gas leaks or fires. Smell also has a huge impact on interpersonal relationships, since olfactory disorders have been associated with poor quality of life, depression, mood swings, worries about personal hygiene, loss of appetite and cooking difficulties.

"Olfactory dysfunctions have a negative impact on daily life, health and safety," says Dr. Fortin. "It is important to pay attention to this symptom once a patient's condition has been stabilized following a traumatic brain injury."

(Photo: IStock)

Université de Montréal

GREAT APES KNOW THEY COULD BE WRONG

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Great apes – orangutans, chimpanzees, bonobos and gorillas – realize that they can be wrong when making choices, according to Dr. Josep Call from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Dr. Call’s study was just published online in Springer’s journal, Animal Cognition.

In a series of three experiments, seven gorillas, eight chimpanzees, four bonobos and seven orangutans, from the Wolfgang Köhler Research Center at the Leipzig Zoo in Germany, were presented with two hollow tubes, one baited with a food reward, the other not. The apes were then observed as they tried to find the reward.

In the first experiment, the apes were prevented from watching the baiting but the tubes were shaken to give them auditory information about the reward’s location instead. Dr. Call wanted to see if when the apes were prevented from acquiring visual information, but offered auditory cues instead, they would be able to use the auditory information to reduce their reliance on visual searching.

In the second experiment, the apes were shown the location where the food was hidden and then at variable time delays encouraged to retrieve it. The purpose of this experiment was to see if forgetting the location would lead to the apes looking harder for it.

In the last experiment, the researcher compared the apes’ response between visible and hidden baiting conditions, when the quality of the food reward varied. The author hypothesized that the apes would check more often when a high quality reward was at stake, irrespective of whether or not they had seen where it was placed.

Although the apes retrieved the reward very accurately when they had watched the baiting, Dr. Call found that they were more likely to check inside the tube before choosing when high stakes were involved, or after a longer period of time had elapsed between the baiting and the retrieval of the reward. In contrast, when the apes were provided with auditory information about the food’s location, they reduced the amount of checking before choosing. According to Dr. Call, taken together, these findings show that the apes were aware that they could be wrong when choosing.

Dr. Call concludes: “The current results indicate that the looking response appears to be a function of at least three factors: the cost of looking inside the tube, the value of the reward and the state of the information. The combination of these three factors creates an information processing system that possesses complexity, flexibility and control, three of the features of metacognition (cognition about cognition, or knowing about knowing). These findings suggest that nonhuman animals may possess some metacognitive abilities, too.”

Springer

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