Tag: RedOrbit

Junk food makes rats lose appetite for balanced diet

Coverage: Scientific American, TIME, CNN, Discovery News, IFLS, Newsweek, RedOrbit

A diet of junk food not only makes rats fat, but also reduces their appetite for novel foods, a preference that normally drives them to seek a balanced diet, reports a study published in the open-access journal Frontiers in Psychology.

The study helps to explain how excessive consumption of junk food can change behavior, weaken self-control and lead to overeating and obesity.
The team of researchers, led by Professor Margaret Morris, Head of Pharmacology from the School of Medical Sciences, UNSW Australia, taught young male rats to associate each of two different sound cues with a particular flavor of sugar water – cherry and grape.

Healthy rats, raised on a healthy diet, stopped responding to cues linked to a flavor in which they have recently overindulged. This inborn mechanism, widespread in animals, protects against overeating and promotes a healthy, balanced diet.

But after 2 weeks on a diet that included daily access to cafeteria foods, including pie, dumplings, cookies, and cake – with 150% more calories – the rats’ weight increased by 10% and their behavior changed dramatically. They became indifferent in their food choices and no longer avoided the sound advertising the overfamiliar taste. This indicated that they had lost their natural preference for novelty. The change even lasted for some time after the rats returned to a healthy diet.

The researchers think that a junk diet causes lasting changes in the reward circuit parts of the rats’ brain, for example, the orbitofrontal cortex, an area of the brain responsible for decision-making. They say these results may have implications for people’s ability to limit their intake of certain kinds of foods, because the brain’s reward circuitry is similar in all mammals.
“The interesting thing about this finding is that if the same thing happens in humans, eating junk food may change our responses to signals associated with food rewards,” says UNSW Professor Morris. “It’s like you’ve just had ice cream for lunch, yet you still go and eat more when you hear the ice cream van come by.”

The World Health Organization estimates that over 10% of the world’s adult population is obese and at least 2.8 million people die each year as a result of being overweight or obesity. Overweight and obesity are major risk factors for a number of chronic diseases, including diabetes, cardiovascular diseases and cancer.

“As the global obesity epidemic intensifies, advertisements may have a greater effect on people who are overweight and make snacks like chocolate bars harder to resist,” adds Dr Amy Reichelt, lead author of the paper and UNSW postdoctoral associate.

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2014-08/f-jfm082514.php

Study: http://journal.frontiersin.org/article/10.3389/fpsyg.2014.00852/full

Do you have a sweet tooth? Honeybees have a sweet claw

Selected coverage: Discovery News, Yahoo, Süddeutsche Zeitung, RedOrbit

New research on the ability of honeybees to taste with claws on their forelegs reveals details on how this information is processed, according to a study published in the open-access journal, Frontiers in Behavioral Neuroscience.

Insects taste through sensilla, hair-like structures on the body that contain receptor nerve cells, each of which is sensitive to a particular substance. In many insects, for example the honeybee, sensilla are found on the mouthparts, antenna and the tarsi – the end part of the legs. Honeybees weigh information from both front tarsi to decide whether to feed, finds the latest study led by Dr. Gabriela de Brito Sanchez, researcher, University of Toulouse, and Dr. Martin Giurfa, Director of the Research Centre on Animal Cognition, University of Toulouse, France.

Hundreds of honeybees were included in the study. Sugary, bitter and salty solutions were applied to the tarsi of the forelegs to test if this stimulated the bees to extend or retract their tongue – reflex actions that indicate whether or not they like the taste and are preparing to drink. Results revealed that honeybee tarsi are highly sensitive to sugar: even dilute sucrose solutions prompted the bees to extend their tongue. Measurements of nerve cell activity showed that the part of the honeybee tarsus most sensitive to sugary tastes is the double claw at its end. Also, the segments of the tarsus before the claws, known as the tarsomeres, were found to be highly sensitive to saline solutions.

“Honeybees rely on their color vision, memory, and sense of smell and taste to find nectar and pollen in the ever-changing environment around the colony,” says Dr. Giurfa. “The high sensitivity to salts of the tarsomeres and to sugar of the tarsal claws is impressive given that each tarsus has fewer sensilla than the other sense organs. The claw’s sense of taste allows workers to detect nectar immediately when they land on flowers. Also, bees hovering over water ponds can promptly detect the presence of salts in water through the tarsomeres of their hanging legs.”

But what if honeybees receive contradictory information, for example, about tasty sucrose from the right foreleg, but about water or distasteful caffeine from the left? The central nervous system of honeybees weighs this information from both sides, but unequally: input from the side that is first to taste something tasty or distasteful counts for more. For example, if a bee first tasted sucrose on one side, she would typically extend her tongue and subsequently ignore less attractive tastes on the other. But if the order was reversed, she was around 50% less likely than normally to extend her tongue for sucrose.

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2014-02/f-dyh013114.php

Study: http://journal.frontiersin.org/article/10.3389/fnbeh.2014.00025/full

Domestication of dogs may have elaborated on a pre-existing capacity of wolves to learn from humans

Selected coverage: Wiener Zeitung, Huffington Post, Tribune de Genève, RedOrbit, ABC News

Wolves can learn from observing humans and pack members where food is hidden and recognize when humans only pretend to hide food, reports a study for the first time in the open-access journal Frontiers in Psychology. These findings imply that when our ancestors started to domesticate dogs, they could have built on a pre-existing ability of wolves to learn from others, not necessarily pack members.

A paper published recently in the journal Science suggested that humans domesticated dogs about 18 thousand years ago, possibly from a European population of grey wolves that is now extinct. But it remains unknown how much the ability of dogs to communicate with people derives from pre-existing social skills of their wolf ancestors, rather than from novel traits that arose during domestication.

In a recent study, Friederike Range and Zsófia Virányi from the Messerli Research Institute at the University of Veterinary Medicine Vienna investigated if wolves and dogs can observe a familiar “demonstrator” – a human or a specially trained dog – to learn where to look for food within a meadow. The subjects were 11 North American grey wolves and 14 mutts, all between 5 and 7 months old, born in captivity, bottle-fed, and hand-raised in packs at the Wolf Science Center of Game Park Ernstbrunn, Austria.

The wolves and dogs were two to four times more likely to find the snack after watching a human or dog demonstrator hide it, and this implies that they had learnt from the demonstration instead of only relying on their sense of smell. Moreover, they rarely looked for the food when the human demonstrator had only pretended to hide it, and this proves that they had watched very carefully.

The wolves were less likely to follow dog demonstrators to hidden food. This does not necessarily mean that they were not paying attention to dog demonstrators: on the contrary, the wolves may have been perceptive enough to notice that the demonstrator dogs did not find the food reward particularly tasty themselves, and so simply did not bother to look for it.

The researchers conclude that the ability to learn from other species, including humans, is not unique to dogs but was already present in their wolf ancestors. Prehistoric humans and the ancestors of dogs could build on this ability to better coordinate their actions.

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2013-12/f-dod120213.php

Study: http://journal.frontiersin.org/article/10.3389/fpsyg.2013.00868/full