Arquivo da tag: Neurofisiologia

Tamed fox shows domestication’s effects on the brain (Science News)

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Gene activity changes accompany doglike behavior

By Tina Hesman Saey

Web edition: May 15, 2013

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Taming silver foxes (shown) alters their behavior. A new study links those behavior changes to changes in brain chemicals. Tom Reichner/Shutterstock

COLD SPRING HARBOR, N.Y. – Taming foxes changes not only the animals’ behavior but also their brain chemistry, a new study shows.

The finding could shed light on how the foxes’ genetic cousins, wolves, morphed into man’s best friend. Lenore Pipes of Cornell University presented the results May 10 at the Biology of Genomes conference.

The foxes she worked with come from a long line started in 1959 when a Russian scientist named Dmitry Belyaev attempted to recreate dog domestication, but using foxes instead of wolves. He bred silver foxes (Vulpes vulpes), which are actually a type of red fox with white-tipped black fur. Belyaev and his colleagues selected the least aggressive animals they could find at local fox farms and bred them. Each generation, the scientists picked the tamest animals to mate, creating ever friendlier foxes. Now, more than 50 years later, the foxes act like dogs, wagging their tails, jumping with excitement and leaping into the arms of caregivers for caresses.

At the same time, the scientists also bred the most aggressive foxes on the farms. The descendents of those foxes crouch, flatten their ears, growl, bare their teeth and lunge at people who approach their cages.

The foxes’ tame and aggressive behaviors are rooted in genetics, but scientists have not found DNA changes that account for the differences. Rather than search for changes in genes themselves, Pipes and her colleagues took an indirect approach, looking for differences in the activity of genes in the foxes’ brains.

The team collected two brain parts, the prefrontal cortex and amygdala, from a dozen aggressive foxes and a dozen tame ones. The prefrontal cortex, an area at the front of the brain, is involved in decision making and in controlling social behavior, among other tasks. The amygdala, a pair of almond-size regions on either side of the brain, helps process emotional information.

Pipes found that the activity of hundreds of genes in the two brain regions differed between the groups of affable and hostile foxes. For example, aggressive animals had increased activity of some genes for sensing dopamine. Pipes speculated that tame animals’ lower levels of dopamine sensors might make them less anxious.

The team had expected to find changes in many genes involved in serotonin signaling, a process targeted by some popular antidepressants such as Prozac. Tame foxes are known to have more serotonin in their brains. But only one gene for sensing serotonin had higher activity in the friendly animals.

In a different sort of analysis, Pipes discovered that all aggressive foxes carry one form of the GRM3 glutamate receptor gene, while a majority of the friendly foxes have a different variant of the gene. In people, genetic variants of GRM3 have been linked to schizophrenia, bipolar disorder and other mood disorders. Other genes involved in transmitting glutamate signals, which help regulate mood, had increased activity in tame foxes, Pipes said.

It is not clear whether similar brain chemical changes accompanied the transformation of wolves into dogs, said Adam Freedman, an evolutionary biologist at Harvard University. Even if dogs and wolves now have differing brain chemical levels, researchers can’t turn back time to watch the process unfold; they can only guess at how domestication happened. “We have to reconstruct an unobservable series of steps,” he said. Pipes’ study is an interesting example of what might have happened to dogs’ brains during domestication, he said.

Red Brain, Blue Brain: Republicans and Democrats Process Risk Differently, Research Finds (Science Daily)

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Feb. 13, 2013 — A team of political scientists and neuroscientists has shown that liberals and conservatives use different parts of the brain when they make risky decisions, and these regions can be used to predict which political party a person prefers. The new study suggests that while genetics or parental influence may play a significant role, being a Republican or Democrat changes how the brain functions.

Republicans and Democrats differ in the neural mechanisms activated while performing a risk-taking task. Republicans more strongly activate their right amygdala, associated with orienting attention to external cues. Democrats have higher activity in their left posterior insula, associated with perceptions of internal physiological states. This activation also borders the temporal-parietal junction, and therefore may reflect a difference in internal physiological drive as well as the perception of the internal state and drive of others. (Credit: From: Darren Schreiber, Greg Fonzo, Alan N. Simmons, Christopher T. Dawes, Taru Flagan, James H. Fowler, Martin P. Paulus. Red Brain, Blue Brain: Evaluative Processes Differ in Democrats and Republicans. PLoS ONE, 2013; 8 (2): e52970 DOI: 10.1371/journal.pone.0052970)

Dr. Darren Schreiber, a researcher in neuropolitics at the University of Exeter, has been working in collaboration with colleagues at the University of California, San Diego on research that explores the differences in the way the brain functions in American liberals and conservatives. The findings are published Feb. 13 in the journalPLOS ONE.

In a prior experiment, participants had their brain activity measured as they played a simple gambling game. Dr. Schreiber and his UC San Diego collaborators were able to look up the political party registration of the participants in public records. Using this new analysis of 82 people who performed the gambling task, the academics showed that Republicans and Democrats do not differ in the risks they take. However, there were striking differences in the participants’ brain activity during the risk-taking task.

Democrats showed significantly greater activity in the left insula, a region associated with social and self-awareness. Meanwhile Republicans showed significantly greater activity in the right amygdala, a region involved in the body’s fight-or-flight system. These results suggest that liberals and conservatives engage different cognitive processes when they think about risk.

In fact, brain activity in these two regions alone can be used to predict whether a person is a Democrat or Republican with 82.9% accuracy. By comparison, the longstanding traditional model in political science, which uses the party affiliation of a person’s mother and father to predict the child’s affiliation, is only accurate about 69.5% of the time. And another model based on the differences in brain structure distinguishes liberals from conservatives with only 71.6% accuracy.

The model also outperforms models based on differences in genes. Dr. Schreiber said: “Although genetics have been shown to contribute to differences in political ideology and strength of party politics, the portion of variation in political affiliation explained by activity in the amygdala and insula is significantly larger, suggesting that affiliating with a political party and engaging in a partisan environment may alter the brain, above and beyond the effect of heredity.”

These results may pave the way for new research on voter behaviour, yielding better understanding of the differences in how liberals and conservatives think. According to Dr. Schreiber: “The ability to accurately predict party politics using only brain activity while gambling suggests that investigating basic neural differences between voters may provide us with more powerful insights than the traditional tools of political science.”

Journal Reference:

  1. Darren Schreiber, Greg Fonzo, Alan N. Simmons, Christopher T. Dawes, Taru Flagan, James H. Fowler, Martin P. Paulus. Red Brain, Blue Brain: Evaluative Processes Differ in Democrats and Republicans. PLoS ONE, 2013; 8 (2): e52970 DOI:10.1371/journal.pone.0052970

Are Bacteria Making You Hungry? (Science Daily)

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Dec. 19, 2012 — Over the last half decade, it has become increasingly clear that the normal gastrointestinal (GI) bacteria play a variety of very important roles in the biology of human and animals. Now Vic Norris of the University of Rouen, France, and coauthors propose yet another role for GI bacteria: that they exert some control over their hosts’ appetites. Their review was published online ahead of print in the Journal of Bacteriology.

Are bacteria making you hungry? Over the last half decade, it has become increasingly clear that the normal gastrointestinal (GI) bacteria play a variety of very important roles in the biology of human and animals. (Credit: © fabiomax / Fotolia)

This hypothesis is based in large part on observations of the number of roles bacteria are already known to play in host biology, as well as their relationship to the host system. “Bacteria both recognize and synthesize neuroendocrine hormones,” Norris et al. write. “This has led to the hypothesis that microbes within the gut comprise a community that forms a microbial organ interfacing with the mammalian nervous system that innervates the gastrointestinal tract.” (That nervous system innervating the GI tract is called the “enteric nervous system.” It contains roughly half a billion neurons, compared with 85 billion neurons in the central nervous system.)

“The gut microbiota respond both to both the nutrients consumed by their hosts and to the state of their hosts as signaled by various hormones,” write Norris et al. That communication presumably goes both ways: they also generate compounds that are used for signaling within the human system, “including neurotransmitters such as GABA, amino acids such as tyrosine and tryptophan — which can be converted into the mood-determining molecules, dopamine and serotonin” — and much else, says Norris.

Furthermore, it is becoming increasingly clear that gut bacteria may play a role in diseases such as cancer, metabolic syndrome, and thyroid disease, through their influence on host signaling pathways. They may even influence mood disorders, according to recent, pioneering studies, via actions on dopamine and peptides involved in appetite. The gut bacterium,Campilobacter jejuni, has been implicated in the induction of anxiety in mice, says Norris.

But do the gut flora in fact use their abilities to influence choice of food? The investigators propose a variety of experiments that could help answer this question, including epidemiological studies, and “experiments correlating the presence of particular bacterial metabolites with images of the activity of regions of the brain associated with appetite and pleasure.”

Journal Reference:

  1. V. Norris, F. Molina, A. T. Gewirtz. Hypothesis: bacteria control host appetites. Journal of Bacteriology, 2012; DOI:10.1128/JB.01384-12

Brazilian Mediums Shed Light On Brain Activity During a Trance State (Science Daily)

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ScienceDaily (Nov. 16, 2012) — Researchers at Thomas Jefferson University and the University of Sao Paulo in Brazil analyzed the cerebral blood flow (CBF) of Brazilian mediums during the practice of psychography, described as a form of writing whereby a deceased person or spirit is believed to write through the medium’s hand. The new research revealed intriguing findings of decreased brain activity during the mediums’ dissociative state which generated complex written content. Their findings will appear in the November 16th edition of the online journal PLOS ONE.

The 10 mediums — five less expert and five experienced — were injected with a radioactive tracer to capture their brain activity during normal writing and during the practice of psychography which involves the subject entering a trance-like state. The subjects were scanned using SPECT (single photon emission computed tomography) to highlight the areas of the brain that are active and inactive during the practice.

“Spiritual experiences affect cerebral activity, this is known. But, the cerebral response to mediumship, the practice of supposedly being in communication with, or under the control of the spirit of a deceased person, has received little scientific attention, and from now on new studies should be conducted,” says Andrew Newberg, MD, director of Research at the Jefferson-Myrna Brind Center of Integrative Medicine and a nationally-known expert on spirituality and the brain, who collaborated with Julio F. P. Peres, Clinical Psychologist, PhD in Neuroscience and Behavior, Institute of Psychology at the University of Sao Paulo in Brazil, and colleagues on the research.

The mediums ranged from 15 to 47 years of automatic writing experience, performing up to 18 psychographies per month. All were right-handed, in good mental health, and not currently using any psychiatric drugs. All reported that during the study, they were able to reach their usual trance-like state during the psychography task and were in their regular state of consciousness during the control task.

The researchers found that the experienced psychographers showed lower levels of activity in the left hippocampus (limbic system), right superior temporal gyrus, and the frontal lobe regions of the left anterior cingulate and right precentral gyrus during psychography compared to their normal (non-trance) writing. The frontal lobe areas are associated with reasoning, planning, generating language, movement, and problem solving, perhaps reflecting an absence of focus, self-awareness and consciousness during psychography, the researchers hypothesize.

Less expert psychographers showed just the opposite — increased levels of CBF in the same frontal areas during psychography compared to normal writing. The difference was significant compared to the experienced mediums. This finding may be related to their more purposeful attempt at performing the psychography. The absence of current mental disorders in the groups is in line with current evidence that dissociative experiences are common in the general population and not necessarily related to mental disorders, especially in religious/spiritual groups. Further research should address criteria for distinguishing between healthy and pathological dissociative expressions in the scope of mediumship.

The writing samples produced were also analyzed and it was found that the complexity scores for the psychographed content were higher than those for the control writing across the board. In particular, the more experienced mediums showed higher complexity scores, which typically would require more activity in the frontal and temporal lobes, but this was not the case. Content produced during psychographies involved ethical principles, the importance of spirituality, and bringing together science and spirituality.

Several possible hypotheses for these many differences have been considered. One speculation is that as frontal lobe activity decreases, the areas of the brain that support mediumistic writing are further disinhibited (similar to alcohol or drug use) so that the overall complexity can increase. In a similar manner, improvisational music performance is associated with lower levels of frontal lobe activity which allows for more creative activity. However, improvisational music performance and alcohol/drug consumption states are quite peculiar and distinct from psychography. “While the exact reason is at this point elusive, our study suggests there are neurophysiological correlates of this state,” says Newberg.

“This first-ever neuroscientific evaluation of mediumistic trance states reveals some exciting data to improve our understanding of the mind and its relationship with the brain. These findings deserve further investigation both in terms of replication and explanatory hypotheses,” states Newberg.

Journal Reference:

  1. Julio Fernando Peres, Alexander Moreira-Almeida, Leonardo Caixeta, Frederico Leao, Andrew Newberg. Neuroimaging during Trance State: A Contribution to the Study of Dissociation. PLoS ONE, 2012; 7 (11): e49360 DOI:10.1371/journal.pone.0049360

Books Change How a Child’s Brain Grows (Wired)

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By Moheb Costandi, ScienceNOW – October 18, 2012

Image: Peter Dedina/Flickr

NEW ORLEANS, LOUISIANA — Books and educational toys can make a child smarter, but they also influence how the brain grows, according to new research presented here on Sunday at the annual meeting of the Society for Neuroscience. The findings point to a “sensitive period” early in life during which the developing brain is strongly influenced by environmental factors.

Studies comparing identical and nonidentical twins show that genes play an important role in the development of the cerebral cortex, the thin, folded structure that supports higher mental functions. But less is known about how early life experiences influence how the cortex grows.

To investigate, neuroscientist Martha Farah of the University of Pennsylvania and her colleagues recruited 64 children from a low-income background and followed them from birth through to late adolescence. They visited the children’s homes at 4 and 8 years of age to evaluate their environment, noting factors such as the number of books and educational toys in their houses, and how much warmth and support they received from their parents.

More than 10 years after the second home visit, the researchers used MRI to obtain detailed images of the participants’ brains. They found that the level of mental stimulation a child receives in the home at age 4 predicted the thickness of two regions of the cortex in late adolescence, such that more stimulation was associated with a thinner cortex. One region, the lateral inferior temporal gyrus, is involved in complex visual skills such as word recognition.

Home environment at age 8 had a smaller impact on development of these brain regions, whereas other factors, such as the mother’s intelligence and the degree and quality of her care, had no such effect.

Previous work has shown that adverse experiences, such as childhood neglect, abuse, and poverty, can stunt the growth of the brain. The new findings highlight the sensitivity of the growing brain to environmental factors, Farah says, and provide strong evidence that subtle variations in early life experience can affect the brain throughout life.

As the brain develops, it produces more synapses, or neuronal connections, than are needed, she explains. Underused connections are later eliminated, and this elimination process, called synaptic pruning, is highly dependent upon experience. The findings suggest that mental stimulation in early life increases the extent to which synaptic pruning occurs in the lateral temporal lobe. Synaptic pruning reduces the volume of tissue in the cortex. This makes the cortex thinner, but it also makes information processing more efficient.

“This is a first look at how nurture influences brain structure later in life,” Farah reported at the meeting. “As with all observational studies, we can’t really speak about causality, but it seems likely that cognitive stimulation experienced early in life led to changes in cortical thickness.”

She adds, however, that the research is still in its infancy, and that more work is needed to gain a better understanding of exactly how early life experiences impact brain structure and function.

The findings add to the growing body of evidence that early life is a period of “extreme vulnerability,” says psychiatrist Jay Giedd, head of the brain imaging unit in the Child Psychiatry Branch at the National Institute of Mental Health in Bethesda, Maryland. But early life, he says, also offers a window of opportunity during which the effects of adversity can be offset. Parents can help young children develop their cognitive skills by providing a stimulating environment.

Evolution mostly driven by brawn, not brains (University College London)

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Public release date: 15-Oct-2012
By Clare Ryan
University College London

The most common measure of intelligence in animals, brain size relative to body size, may not be as dependent on evolutionary selection on the brain as previously thought, according to a new analysis by scientists.

Brain size relative to body size has been used by generations of scientists to predict an animal’s intelligence. For example, although the human brain is not the largest in the animal kingdom in terms of volume or mass, it is exceptionally large considering our moderate body mass.

Now, a study by a team of scientists at UCL, the University of Konstanz, and the Max Planck Institute of Ornithology has found that the relationship between the two traits is driven by different evolutionary mechanisms in different animals.

Crucially, researchers have found that the most significant factor in determining relative brain size is often evolutionary pressure on body size, and not brain size. For example, the evolutionary history of bats reveals they decreased body size much faster than brain size, leading to an increase in relative brain size. As a result, small bats were able to evolve improved flying manoeuvrability while maintaining the brainpower to handle foraging in cluttered environments.

This shows that relative brain size can not be used unequivocally as evidence of selection for intelligence. The study is published today in the Proceedings of the National Academy of Sciences.

Dr Jeroen Smaers (UCL Anthropology and UCL Genetics, Evolution & Environment), lead author of the study said: “When using brain size relative to body size as a measure of intelligence, the assumption has always been that this measure is primarily driven by changes in brain size. It now appears that the relationship between changes in brain and body size in animals is more complex than has long been assumed.

“Changes in body size often occur independently of changes in brain size and vice versa. Moreover, the nature of these independent changes in brain and body size, are different in different groups of animals.”

Researchers at UCL gathered data on brain and body mass for hundreds of modern and extinct bats, carnivorans, and primates. They then charted brain and body size evolution over time for each species. Across millions of years, most animals increased body size faster than brain size, with the exception of bats.

In primate lineages decreases in brain size marginally outpaced those in body size. Carnivoran evolution has taken yet a different course, with changes generally more strongly associated with body size rather than selection on brain size and cognition.

Given such differences, the authors believe that the predominant interpretation of relative brain size as the consequence of selection on intelligence inherently masks the often more significant influence of selection on body size.