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Centenas de novos genes podem estar por trás da inteligência – mas também autismo e depressão

Many genes work together in the brain to cause complex behavior such as intelligence or anxiety.

HELEN TOLOKONOVA/ALAMY STOCK PHOTO

Hundreds of new genes may underlie intelligence—but also autism and depression

Being smart is a double-edged sword. Intelligent people appear to live longer, but many of the genes behind brilliance can also lead to autism, anxiety, and depression, according to two new massive genetic studies. The work also is one of the first to identify the specific cell types and genetic pathways tied to intelligence and mental health, potentially paving the way for new ways to improve education, or therapies to treat neurotic behavior.

The studies provide some of the first “hard evidence of the many genes and pathways” that work together in complex ways to build smart brains and keep them in balance, says geneticist Peter Visscher of the Queensland Brain Institute at The University of Queensland in Brisbane, Australia, who was not involved in the work.

Researchers have long known that people often inherit intelligence and some personality disorders from their parents. (Environmental factors such as education and stress also profoundly shape intelligence and mental health.) But geneticists have had trouble identifying more than a handful of genes associated with intelligence. Last year, researchers used new statistical methods that can detect strong associations between genes and specific traits to analyze health and genetic records in huge data sets. This led to the discovery of 52 genes linked to intelligence in 80,000 people.

Now, the same team has added almost 1000 genes to that list. Researchers led by geneticist Danielle Posthuma of Vrije University in Amsterdam scoured 14 databases of health and genetic records to identify 939 new genes associated with intelligence in 250,000 individuals. (The data sets measured intelligence with scores on tests of abilities such as mathematics, synonyms, and logic.) Many variants of genes associated with higher intelligence turned up in people who also lived longer and did not have Alzheimer’s disease, attention-deficit hyperactivity disorder, or schizophrenia, the team reports today in Nature Genetics, suggesting that intelligence protects against these disorders. On the downside, genes associated with intelligence correlated with a higher risk for autism.

In a separate study also published today in Nature Genetics, Posthuma and her colleagues identified 500 genes associated with neurotic traits, such as anxiety and depression, by searching the health and genetic records of 449,400 individuals in large databases, such as the UK Biobank, a repository of information on the genetics, health and wellbeing of 500,000 British volunteers, and 23andMe, a personal genomics company in Mountain View, California, with genetic and health data on 5 million customers. They also found that people who worried a lot had inherited different genes than those who were more likely to be depressed, suggesting that there are different underlying genetic pathways for those conditions.

In both studies, the researchers used a new statistical method called MAGMA to quickly search genetic data to identify specific types of cells and tissues where the genes were expressed. Many genes for intelligence were expressed in the “medium spiny neurons” which are part of the basal ganglia, clusters of neurons deep in the brain involved in learning, cognition, and emotion. The researchers also identified many potential targets for developing new pharmaceutical drugs.

“If you can understand the mechanisms at the cell level, you can also look at candidates for medication,” Posthuma says. The same is true for genes for intelligence, she says, which could offer clues to new ways to protect against Alzheimer’s and other disorders.

Répteis que sonham

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Do sleeping dragons dream?

All animals—from humans to birds, worms, and crocodiles—sleep. Not all species sleep alike, however, and scientists have long puzzled over which aspects are truly fundamental. Now, a new study on lizards suggests that sleep states once thought to occur only in mammals and birds have much older evolutionary origins.

Scientists had long suspected that birds and mammals are the only vertebrates to experience rapid eye movement (REM), a sleep state in which the body is mostly immobile but the brain is in overdrive. During REM sleep, the brain generates high-frequency waves of electrical activity and the eyes flicker; in humans, REM is closely linked to dreaming. Punctuating REM are interludes of slow-wave sleep, a state in which brain activity ebbs and the waves become more synchronized. This slower state is widely thought to be important to memory formation and storage.

But scientists who looked for signs of REM and slow-wave sleep in reptiles have had “confusing” results, says Gilles Laurent, a neuroscientist at the Max Planck Institute for Brain Research in Frankfurt, Germany. So when he and colleagues picked up on similar sleep patterns in Australian dragons (Pogona vitticeps) while recording their brain activity for a separate study, it came as a shock.

The team had planned to examine how the lizards—a common pet in Germany—use visual information to chase treats. They continuously recorded the lizards’ brain activity with electrodes over several weeks. At night, the sleeping reptiles’ brains produced rhythms that could be separated into two different patterns—one at very low frequency, about 4HZ, and another, higher frequency about 20HZ, the team reports today in Science. The two frequencies alternated every 40 seconds, reminding Laurent of the regular oscillations between high-frequency REM and slow-wave sleep found in mammals and birds. “The more we looked, the more it appeared as though we were looking at bona fide REM sleep,” he says.

Using an infrared camera, the team found that the sleeping lizards’ eyelids twitched during the REM-like stage, just like other animals. They also found a tantalizingly familiar pattern within the slower phase of the lizards’ brain waves. During this slow phase, electrodes picked up sharp waves of voltage, followed by ripples of electricity that closely resembled patterns seen in humans and rodents. Some scientists believe these waves and ripples help convert new information into memories by replaying past events in fast-forward. Although more studies are still needed to determine whether the function of these brain wave patterns is the same across species, the results suggest that these REM and slow-wave, sleeplike patterns could date all the way back to the common ancestor of reptiles, birds, and mammals, Laurent says.

The “provocative” findings also suggest that “there is something that goes on during sleep that is important to the function of all animals,” says Matt Wilson, a neuroscientist at the Massachusetts Institute of Technology in Cambridge. The lizards could be rehearsing the day’s events as they sleep, forming new memories of all the places they found a snack. Or maybe they’re simply dragons dreaming.

(Video credit: AAAS/Science)

Sobre a seleção sexual em favor dos machos beta (e gama?)

 

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Mais uma teoria de barzinho que poderia ser verdadeira:

A pergunta é: se os machos alfa são favorecidos pela evolução, porque não somos todos machos alfa (na verdade eles são uma minoria da população masculina).

Tenho duas hipóteses complementares sobre isso, todas baseadas no poder de escolha das mulheres.

Primeiro, parece ser muito mais provável que um macho alfa seja violento com sua mulher (porque eles são mais violentos em geral). Assim, mesmo que as mulheres possam sentir desejo por um macho alfa, se forem um pouco mais racionais irão preferir um macho beta (ou gama) que cuide bem delas e dos  filhotes, seja gentil, etc (hoje é o “Dia da Gentileza”, 13/novembro).

Segundo, isso tem a ver com o processo de neotenia que as mulheres impuseram aos homens (neotenia é o que aconteceu durante a domesticação do cão a partir do lobo – favorecimento de caracteres infantis).

Ou seja, se a mulher escolher um macho mais infantil (que não é macho alfa, claro!) , ela terá mais domínio sobre ele, ao fazer o papel de mãe dele e não apenas de parceira sexual. Mulheres maternais são atraentes para os homens (eles gostam de carinho e serem cuidados, comidinha na boca etc) e essa é a mesma raiz do Complexo de Édipo. Na verdade é uma simbiose mutualística, a mulher domina o esposo=filho e o macho é melhor tratado pela esposa=mãe. Essa teoria explica porque os homens (em geral) são bem menos maduros que as mulheres (especialmente na adolescência) e os marmanjos parecem apenas mudar de brinquedos quando crescem:  carrinho vira carrão, jogo de bola vira futebol, brincadeiras de luta e guerra vira filmes de ação e Star Wars.

É claro que, como toda hipótese de psicologia evolucionária, esta sempre tem suas exceções.

Vale notar que o machismo e o patriarcalismo visam primeiramente retirar esse poder de seleção sexual das mulheres (via casamentos arranjados) , a fim de favorecer os machos alfa. Com o fim do patriarcalismo me parece que os machos beta e gama serão cada vez mais favorecidos (embora algumas mulheres reclamem que já não se fazem homens como antigamente, tipo Aragorn e Legolas da Sociedade do Anel). Mas vale lembrar que eles tiveram poucos filhos em comparação com os machos gama Hobbits.