Archive for December 2009
The premise that hunger makes food look more appealing is a widely held belief — just ask those who cruise grocery store aisles on an empty stomach, only to go home with a full basket and an empty wallet.
Prior research studies have suggested that the so-called hunger hormone ghrelin, which the body produces when it’s hungry, might act on the brain to trigger this behavior. New research in mice by UT Southwestern Medical Center scientists suggest that ghrelin might also work in the brain to make some people keep eating “pleasurable” foods when they’re already full.
“What we show is that there may be situations where we are driven to seek out and eat very rewarding foods, even if we’re full, for no other reason than our brain tells us to,” said Dr. Jeffrey Zigman, assistant professor of internal medicine and psychiatry at UT Southwestern and co-senior author of the study appearing online and in a future edition of Biological Psychiatry.
Scientists previously have linked increased levels of ghrelin to intensifying the rewarding or pleasurable feelings one gets from cocaine or alcohol. Dr. Zigman said his team speculated that ghrelin might also increase specific rewarding aspects of eating.
Rewards, he said, generally can be defined as things that make us feel better.
“They give us sensory pleasure, and they motivate us to work to obtain them,” he said. “They also help us reorganize our memory so that we remember how to get them.”
Dr. Mario Perello, postdoctoral researcher in internal medicine and lead author of the current study, said the idea was to determine “why someone who is stuffed from lunch still eats — and wants to eat — that high-calorie dessert.”
For this study, the researchers conducted two standard behavioral tests. In the first, they evaluated whether mice that were fully sated preferred a room where they had previously found high-fat food over one that had only offered regular bland chow. They found that when mice in this situation were administered ghrelin, they strongly preferred the room that had been paired with the high-fat diet. Mice without ghrelin showed no preference.
“We think the ghrelin prompted the mice to pursue the high-fat chow because they remembered how much they enjoyed it,” Dr. Perello said. “It didn’t matter that the room was now empty; they still associated it with something pleasurable.”
The researchers also found that blocking the action of ghrelin, which is normally secreted into the bloodstream upon fasting or caloric restriction, prevented the mice from spending as much time in the room they associated with the high-fat food.
For the second test, the team observed how long mice would continue to poke their noses into a hole in order to receive a pellet of high-fat food. “The animals that didn’t receive ghrelin gave up much sooner than the ones that did receive ghrelin,” Dr. Zigman said.
Humans and mice share the same type of brain-cell connections and hormones, as well as similar architectures in the so-called “pleasure centers” of the brain. In addition, the behavior of the mice in this study is consistent with pleasure- or reward-seeking behavior seen in other animal studies of addiction, Dr. Zigman said.
The next step, Dr. Perello said, is to determine which neural circuits in the brain regulate ghrelin’s actions.
Biological Psychiatry, 2009; DOI: 10.1016/j.biopsych.2009.10.030
Ghrelin Increases the Rewarding Value of High-Fat Diet in an Orexin-Dependent Manner
Mario Perelloa, Ichiro Sakataa, Shari Birnbaumb, Jen-Chieh Chuanga, Sherri Osborne-Lawrencea, Sherry A. Rovinskya, Jakub Woloszyna, Masashi Yanagisawac, Michael Lutterb and Jeffrey M. Zigmana, b, Corresponding Author Contact Information, E-mail The Corresponding Author
a Department of Internal Medicine (Divisions of Hypothalamic Research and Endocrinology & Metabolism), The University of Texas Southwestern Medical Center, Dallas, Texas
b Department of Psychiatry, The University of Texas Southwestern Medical Center, Dallas, Texas
c Department of Molecular Genetics and Howard Hughes Medical Institute, The University of Texas Southwestern Medical Center, Dallas, Texas
Received 12 May 2009;
revised 25 September 2009;
accepted 23 October 2009.
Available online 24 December 2009.
Background Ghrelin is a potent orexigenic hormone that likely impacts eating via several mechanisms. Here, we hypothesized that ghrelin can regulate extra homeostatic, hedonic aspects of eating behavior.
Methods In the current study, we assessed the effects of different pharmacological, physiological, and genetic models of increased ghrelin and/or ghrelin-signaling blockade on two classic behavioral tests of reward behavior: conditioned place preference (CPP) and operant conditioning.
Results Using both CPP and operant conditioning, we found that ghrelin enhanced the rewarding value of high-fat diet (HFD) when administered to ad lib-fed mice. Conversely, wild-type mice treated with ghrelin receptor antagonist and ghrelin receptor-null mice both failed to show CPP to HFD normally observed under calorie restriction. Interestingly, neither pharmacologic nor genetic blockade of ghrelin signaling inhibited the body weight homeostasis-related, compensatory hyperphagia associated with chronic calorie restriction. Also, ghrelin’s effects on HFD reward were blocked in orexin-deficient mice and wild-type mice treated with an orexin 1 receptor antagonist.
Conclusions Our results demonstrate an obligatory role for ghrelin in certain rewarding aspects of eating that is separate from eating associated with body weight homeostasis and that requires the presence of intact orexin signaling.
Key Words: Food intake; food reward; ghrelin; orexin
After Arthur And The Minimoys, now comes Jake And The Megamoys. Na’vi, that is, to be precise.
Next to correspondence in shape and bodysize, i wish the sequence were also on other behalf more like Swift’s “Travels into Several Remote Nations of the World by Lemuel Gulliver”. While that book presented itself as a simple traveller’s narrative with a disingenuous title, it rendered a Menippean Satire in four parts about, by then modern, society and human nature. Next to this, the reader gets the proof, that satire is neither conflicting with SciFi nor good literature.
In Avatar, a paraplegic war veteran Jake, is brought to another planet, Pandora, which is inhabited by the Na’vi, a humanoid race with their own language and culture. He meets the right way of living, misses it and then sets out for a quest to find it again and save it. Sounds familiar? No wonder
In Chrétien de Troyes’ Perceval, the Story of the Grail, written between 1181 and 1190, Perceval, a young guy, virgin and ignorant to the ways of men until the age of 15, meets a crippled Fisher King and sees a grail, not yet identified as “holy”, but he fails to ask a question that would have healed the injured king. Upon learning of his mistake he vows to find the Grail castle again and fulfill his quest but Chretien’s story breaks off soon after, to be continued in a number of different ways by various authors afterwards.
So the plot, known from a medieval bestseller, is knitted into the weaving of Swift’s 18th century block buster, not sparing any stereotype successful in history, from biblical Armaggedon, over eighteenth century sentimentalist “noble savage”, to Westerns .
And while the movie does depict the devastating consequences of material greed, gone wild, it seems to suggest totemistic religiousness as the way out of it. So, people in Afghanistan, perceived as “humanoids” at best, in their cultural alienness, being in the way of hegemonic oil and gas interests, are reconnecting themselves with their nature and send American troups home after deafeat? This naive play with stereotypes does even backfire, however noble its original intentions might be: it promotes a new tribalisation and thus yields a religious justification to the conflicts arrising from globalization worldwide. But this world is not functioning on totemistic idols anymore. Nowadays human rights are remorselessly sacrificed by megalomaniacal fantasies of transnational corporation leaders about an omnipotent international economy through trade, foreign direct investment, capital flows, migration, and the spread of technology. And it is the same human rights in Khabul or Washington, that are at stake.
Rather than adding a third optical dimension, the movie would have deserved a third dimension in depth, if it pretends itself to more than a kiddie’s story. “It wouldn’t be fair to slap the “all style, no substance” label on James Cameron’s latest sci-fi epic, but it’s certainly tempting”, says Jamey Codding. It certainly is. Nonetheless, the movie looks spectacular in 3D. For a pity, the impressive computer graphic realisations are soaked in a pompous melodramatic sound carpet that sounds like Wagner on Glühwein. Some music would not have done any harm.
Alas, if it did not turn out well this time, there are still Part III: A Voyage to Laputa, Balnibarbi, Glubbdubdrig, Luggnagg, and Japan and Part IV: A Voyage to Houyhnhnms to try again…
Researchers at the University of California, Berkeley, are challenging long-held beliefs that human beings are wired to be selfish. In a wide range of studies, social scientists are amassing a growing body of evidence to show we are evolving to become more compassionate and collaborative in our quest to survive and thrive.
In contrast to “every man for himself” interpretations of Charles Darwin’s theory of evolution by natural selection, Dacher Keltner, a UC Berkeley psychologist and author of “Born to be Good: The Science of a Meaningful Life,” and his fellow social scientists are building the case that humans are successful as a species precisely because of our nurturing, altruistic and compassionate traits.
They call it “survival of the kindest.”
“Because of our very vulnerable offspring, the fundamental task for human survival and gene replication is to take care of others,” said Keltner, co-director of UC Berkeley’s Greater Good Science Center. “Human beings have survived as a species because we have evolved the capacities to care for those in need and to cooperate. As Darwin long ago surmised, sympathy is our strongest instinct.”
Empathy in our genes
Keltner’s team is looking into how the human capacity to care and cooperate is wired into particular regions of the brain and nervous system. One recent study found compelling evidence that many of us are genetically predisposed to be empathetic.
The study, led by UC Berkeley graduate student Laura Saslow and Sarina Rodrigues of Oregon State University, found that people with a particular variation of the oxytocin gene receptor are more adept at reading the emotional state of others, and get less stressed out under tense circumstances.
Informally known as the “cuddle hormone,” oxytocin is secreted into the bloodstream and the brain, where it promotes social interaction, nurturing and romantic love, among other functions.
“The tendency to be more empathetic may be influenced by a single gene,” Rodrigues said.
The more you give, the more respect you get
While studies show that bonding and making social connections can make for a healthier, more meaningful life, the larger question some UC Berkeley researchers are asking is, “How do these traits ensure our survival and raise our status among our peers?”
One answer, according to UC Berkeley social psychologist and sociologist Robb Willer is that the more generous we are, the more respect and influence we wield. In one recent study, Willer and his team gave participants each a modest amount of cash and directed them to play games of varying complexity that would benefit the “public good.” The results, published in the journal American Sociological Review, showed that participants who acted more generously received more gifts, respect and cooperation from their peers and wielded more influence over them.
“The findings suggest that anyone who acts only in his or her narrow self-interest will be shunned, disrespected, even hated,” Willer said. “But those who behave generously with others are held in high esteem by their peers and thus rise in status.”
“Given how much is to be gained through generosity, social scientists increasingly wonder less why people are ever generous and more why they are ever selfish,” he added.
Cultivating the greater good
Such results validate the findings of such “positive psychology” pioneers as Martin Seligman, a professor at the University of Pennsylvania whose research in the early 1990s shifted away from mental illness and dysfunction, delving instead into the mysteries of human resilience and optimism.
While much of the positive psychology being studied around the nation is focused on personal fulfillment and happiness, UC Berkeley researchers have narrowed their investigation into how it contributes to the greater societal good.
One outcome is the campus’s Greater Good Science Center, a West Coast magnet for research on gratitude, compassion, altruism, awe and positive parenting, whose benefactors include the Metanexus Institute, Tom and Ruth Ann Hornaday and the Quality of Life Foundation.
Christine Carter, executive director of the Greater Good Science Center, is creator of the “Science for Raising Happy Kids” Web site, whose goal, among other things, is to assist in and promote the rearing of “emotionally literate” children. Carter translates rigorous research into practical parenting advice. She says many parents are turning away from materialistic or competitive activities, and rethinking what will bring their families true happiness and well-being.
“I’ve found that parents who start consciously cultivating gratitude and generosity in their children quickly see how much happier and more resilient their children become,” said Carter, author of “Raising Happiness: 10 Simple Steps for More Joyful Kids and Happier Parents” which will be in bookstores in February 2010. “What is often surprising to parents is how much happier they themselves also become.”
The sympathetic touch
As for college-goers, UC Berkeley psychologist Rodolfo Mendoza-Denton has found that cross-racial and cross-ethnic friendships can improve the social and academic experience on campuses. In one set of findings, published in the Journal of Personality and Social Psychology, he found that the cortisol levels of both white and Latino students dropped as they got to know each over a series of one-on-one get-togethers. Cortisol is a hormone triggered by stress and anxiety.
Meanwhile, in their investigation of the neurobiological roots of positive emotions, Keltner and his team are zeroing in on the aforementioned oxytocin as well as the vagus nerve, a uniquely mammalian system that connects to all the body’s organs and regulates heart rate and breathing.
Both the vagus nerve and oxytocin play a role in communicating and calming. In one UC Berkeley study, for example, two people separated by a barrier took turns trying to communicate emotions to one another by touching one other through a hole in the barrier. For the most part, participants were able to successfully communicate sympathy, love and gratitude and even assuage major anxiety.
Researchers were able to see from activity in the threat response region of the brain that many of the female participants grew anxious as they waited to be touched. However, as soon as they felt a sympathetic touch, the vagus nerve was activated and oxytocin was released, calming them immediately.
“Sympathy is indeed wired into our brains and bodies; and it spreads from one person to another through touch,” Keltner said.
The same goes for smaller mammals. UC Berkeley psychologist Darlene Francis and Michael Meaney, a professor of biological psychiatry and neurology at McGill University, found that rat pups whose mothers licked, groomed and generally nurtured them showed reduced levels of stress hormones, including cortisol, and had generally more robust immune systems.
Overall, these and other findings at UC Berkeley challenge the assumption that nice guys finish last, and instead support the hypothesis that humans, if adequately nurtured and supported, tend to err on the side of compassion.
“This new science of altruism and the physiological underpinnings of compassion is finally catching up with Darwin’s observations nearly 130 years ago, that sympathy is our strongest instinct,” Keltner said.
PNAS December 8, 2009, 106 (49)
Oxytocin receptor genetic variation relates to empathy and stress reactivity in humans
1. Sarina M. Rodrigues a,b,1,2,
2. Laura R. Saslow c,1,2,
3. Natalia Garcia c,
4. Oliver P. John a,c and
5. Dacher Keltner c
+ Author Affiliations
a Institute of Personality and Social Research, University of California, Berkeley, CA 94720;
b Department of Psychology, Oregon State University, Corvallis, OR 97331; and
c Department of Psychology, University of California, Berkeley, CA 94720
↵1 S.M.R and L.R.S. contributed equally to this work.
Edited by Michael I. Posner, University of Oregon, Eugene, OR, and approved October 9, 2009 (received for review August 24, 2009)
Oxytocin, a peptide that functions as both a hormone and neurotransmitter, has broad influences on social and emotional processing throughout the body and the brain. In this study, we tested how a polymorphism (rs53576) of the oxytocin receptor relates to two key social processes related to oxytocin: empathy and stress reactivity. Compared with individuals homozygous for the G allele of rs53576 (GG), individuals with one or two copies of the A allele (AG/AA) exhibited lower behavioral and dispositional empathy, as measured by the “Reading the Mind in the Eyes” Test and an other-oriented empathy scale. Furthermore, AA/AG individuals displayed higher physiological and dispositional stress reactivity than GG individuals, as determined by heart rate response during a startle anticipation task and an affective reactivity scale. Our results provide evidence of how a naturally occurring genetic variation of the oxytocin receptor relates to both empathy and stress profiles.
“For there is nothing either good or bad, but thinking makes it so…” Hamlet by William Shakespeare (Act II – Sc. II).
It appears, that this not so new study yields support to this idea, at least in a social invironment that does exert sufficient pressure on its members with regard to acceptable sexual role behaviour.
Sex Roles Volume 10, Numbers 5-6 / März 1984Volume 10, Numbers 5-6 / März 1984 p. 457-467 doi 10.1007/BF00287562
Androgyny, depression, and self-esteem in irish homosexual and heterosexual males and females.
Helena M. Carlson1 and Leslie A. Baxter1
|(1)||Department of Psychology, Lewis and Clark College, 92719 Portland, Oregon|
Abstract An examination was made of the following research questions: (a) Do Irish homosexuals and heterosexuals differ in the frequency of their classification in sex-role categories? (b) Is sexual orientation related to psychological adjustment? (c) Is androgyny related to psychological adjustment? Subjects were 112 Irish men and women who were administered Bem’s Sex-Role Inventory, Rosenberg’s Self-Esteem Scale, Zung’s Self-Rating Depression Scale, and a questionnaire. Results indicated that Irish homosexuals were classified more frequently than Irish heterosexuals as androgynous. Homosexuals did not differ from heterosexuals in self-esteem or depression scores. Among these Irish subjects, psychological sex-role category is a more powerful influence on psychological health than actual sexual orientation. It is not whether you are homosexual or heterosexual that affects your psychological health, but how you perceive your own psychological masculinity and femininity.