Thursday, August 18, 2011
Thursday, August 11, 2011
Intelligence is in the genes, researchers report
chicagotribune.com
By Eryn Brown, Los Angeles Times
August 10, 2011
Intelligence is in the genes, researchers reported Tuesday in the journal Molecular Psychology.
The international team, led by Ian Deary of the University of Edinburgh in Scotland and Peter Visscher of the Queensland Institute of Medical Research in Brisbane, Australia, compared the DNA of more than 3,500 people, middle aged and older, who also had taken intelligence tests. They calculated that more than 40% of the differences in intelligence among test subjects was associated with genetic variation.
The genome-wide association study, as such broad-sweep genetic studies are known, suggested that humans inherit much of their smarts, and a large number of genes are involved.
Booster Shots asked Deary to answer a few questions about the research. The following is an edited version of our questions and his emailed responses.
What exactly were you looking for when you looked at test subjects' genetic information?
We studied over 3,500 people. We looked at over 500,000 individual locations on the chromosomal DNA where people are known to differ. We looked at the association between those DNA differences and two types of intelligence. One type of intelligence was on-the-spot thinking (fluid intelligence) and the other was vocabulary (crystallized intelligence).
You wrote in your paper that 40% of the variation in crystallized intelligence and 51% of the variation in fluid intelligence is associated with genetic differences. How did you calculate those figures? And where does the rest of intelligence come from? Other genes, or environmental factors?
To estimate the proportion of variance associated with common genetic differences (in what are called single nucleotide polymorphisms, or SNPs) we used a new genetic statistics procedure invented by Professor Visscher and his colleagues in Brisbane, called GCTA. The rest of people's differences in those types of intelligence could come from genetic differences we were not able to capture, or from the environment.
Certainly, twin and adoption studies tell us that the environment makes an important contribution to intelligence differences throughout life, and especially in early childhood.
Is this the first time such a study has been attempted? How have scientists studied the relationship between genes and intelligence in the past?
There have been some studies looking at individual genes and sets of genes. And some smaller studies have been conducted with coarser genetic sweeps. This is the first study to use thousands of people, half a million genetic variants and to apply this new GCTA procedure to
estimate the genetic contribution directly from the genes.
Why would it be surprising that intelligence is an inherited trait? Many people might say this seems obvious.
It is not surprising to find that intelligence differences have some genetic foundation. Twin and adoption studies have been suggesting that for decades. But those studies make assumptions -- for example that the environment is just as similar for non-identical twins as for identical twins -- and people have questioned those assumptions.
Here, we bypass all that and test the DNA. What is not at all obvious is what the genetic contribution is. From our results, we can suggest that a substantial amount of the genetic contribution to intelligence differences comes from many, many small effects from genetic variants that are in linked with common variants (SNPs).
What parts of your study and analysis do you suspect might receive criticism, and on what grounds?
We don't point to individual genes among the 40%-50% of the variance we detected. We need far larger numbers to do that. We know now that it would be better to have ten times or more subjects than we tested.
We did not have exactly the same intelligence tests in each sample, so that might have led us to underestimate some effects. The GCTA procedure is not easy to understand, so it is hard for people to get their head round how the estimate for the genetic contribution is derived.
Autism, ADHD Share Genetic Similarities
Autism, ADHD Share Genetic Similarities
August 11, 2011 | MyHealthNewsDaily
Similar genetic changes found in some people with ADHD and in some with autism may help explain why children with the hyperactivity disorder often have symptoms of other developmental disorders, a new study reports.
The study identified several genetic changes that are present in a small portion of both attention deficit hyperactivity disorder (ADHD) patients and autism patients, and that are absent in people without these disorders.
Although it has been known that some autism and ADHD patients have certain rare genes in common, this is the first study "to compare the two conditions head to head, in an identical way," said study researcher Russell Schachar, senior scientist of psychiatry at the Hospital for Sick Children in Toronto.
In addition to finding a genetic overlap between the conditions, the study identified several genes not previously known to be involved in ADHD.
The research was published online Aug. 10 in the journal Science Translational Medicine.
Attention and autism
ADHD, a condition characterized by inattention, hyperactivity and impulsiveness, affects 4 percent of school-age children worldwide. Autism and its related disorders, whose symptoms include difficulty with social interactions and communication, affect approximately one of every 300 children. Scientists suspect that a combination of environmental and inherited factors leads to both conditions, but the specifics of the genetic pathways involved remain unclear, the researchers said.
Over the course of five years, the study researchers collected DNA and behavioral data from 248 children with ADHD and from 349 children with autism. Because these conditions can be misdiagnosed, the researchers first made sure the participants truly had them.
"We do one of the most painstaking kinds of assessments in ADHD literature," Schachar said. "It took essentially a day per participant."
The researchers analyzed the DNA of both groups of children, looking for a type of genetic change known as copy number variations (CNVs). In CNVs, a stretch of DNA includes a certain sequence repeated either too many or too few times. When the researchers compared the CNVs of ADHD patients with those of the autistic patients, they discovered several CNVs common to some members of both groups.
Twenty-two kids with ADHD had a CNV not found in healthy kids, and five of those kids had CNVs that also appeared in nine kids with autism, Schachar said.
"I would just characterize that as a modest amount of overlap, but overlap nonetheless," Schachar told MyHealthNewsDaily.
A link to other psychiatric disorders
"It's an interesting paper," said Dr. Joachim Hallmayer, associate professor of psychiatry at Stanford University who was not involved with the study.
But because Schachar's team found only a small number of instances of shared CNVs, Hallmayer said, "the big question is whether there are more of these rare alleles."
Schachar acknowledged that the number of ADHD and autism patients with these CNVs in common is small, but said it is still significant. The take-away message of the study is that "the genetic aspects of ADHD may be shared with other neurodevelopmental disorders, and we better figure out how that works," he said.
The specific find that Schachar called "most exciting" was the prevalence of mutations in the gene ASTN2, which is involved in the development of neurons. After discovering CNVs in ASTN2 in a few kids in both the ADHD and autism groups, the researchers further analyzed all the DNA samples from both groups of kids, and discovered other types of changes in that gene in eight more children with ADHD, and nine with autism.
These findings may indicate that disruption of this gene "is associated with a higher risk for neurophsychiatric disorder in general," the authors reported.
"Clearly these are genes that affect the development of the brain," Schachar said. But why changes in these genes "would be shaped into one disorder in one person and a different disorder in another person is going to be a question for a long time, I'm sure."
Monday, August 1, 2011
Existence: Where did my consciousness come from?
29 July 2011 by Anil Ananthaswamyhttp://tinyurl.com/3h5ln4s
THINK for a moment about a time before you were born. Where were you? Now think ahead to a time after your death. Where will you be? The brutal answer is: nowhere. Your life is a brief foray on Earth that started one day for no reason and will inevitably end.
But what a foray. Like the whole universe, your consciousness popped into existence out of nothingness and has evolved into a rich and complex entity full of wonder and mystery.
Contemplating this leads to a host of mind-boggling questions. What are the odds of my consciousness existing at all? How can such a thing emerge from nothingness? Is there any possibility of it surviving my death? And what is consciousness anyway?
Answering these questions is incredibly difficult. Philosopher Thomas Nagel once asked, "What is it like to be a bat?" Your response might be to imagine flying around in the dark, seeing the world in the echoes of high-frequency sounds. But that isn't the answer Nagel was looking for. He wanted to emphasise that there is no way of knowing what it is like for a bat to feel like a bat. That, in essence, is the conundrum of consciousness.
Neuroscientists and philosophers fall into two broad camps. One thinks that consciousness is an emergent property of the brain and that once we fully understand the intricate workings of neuronal activity, consciousness will be laid bare. The other doubts it will be that simple. They agree that consciousness emerges from the brain, but argue that Nagel's question will always remain unanswered: knowing every detail of a bat's brain cannot tell us what it is like to be a bat. This is often called the "hard problem" of consciousness, and seems scientifically intractable - for now.
Meanwhile, "there are way too many so-called easy problems to worry about", says Anil Seth of the University of Sussex in Brighton, UK.
One is to look for signatures of consciousness in brain activity, in the hope that this takes us closer to understanding what it is. Various brain areas have been found to be active when we are conscious of something and quiet when we are not. For example, Stanislas Dehaene of the French National Institute of Health and Medical Research in Gif sur Yvette and colleagues have identified such regions in our frontal and parietal lobes (Nature Neuroscience, vol 8, p 1391).
Consciousness explained
This is consistent with a theory of consciousness proposed by Bernard Baars of the Neuroscience Institute in San Diego, California. He posited that most non-conscious experiences are processed in specialised local regions of the brain such as the visual cortex. We only become conscious of this activity when the information is broadcast to a network of neurons called the global workspace - perhaps the regions pinpointed by Dehaene.
But others believe the theory is not telling the whole story. "Does global workspace theory really explain consciousness, or just the ability to report about consciousness?" asks Seth.
Even so, the idea that consciousness seems to be an emergent property of the brain can take us somewhere. For example, it makes the odds of your own consciousness existing the same as the odds of you being born at all, which is to say, very small. Just think of that next time you suffer angst about your impending return to nothingness.
As for whether individual consciousness can continue after death, "it is extremely unlikely that there would be any form of self-consciousness after the physical brain decays", says philosopher Thomas Metzinger of the Johannes Gutenberg University in Mainz, Germany.
Extremely unlikely, but not impossible. Giuilio Tononi of the University of Wisconsin-Madison argues that consciousness is the outcome of how complex matter, including the brain, integrates information. "According to Tononi's theory, if one could build a device or a system that integrated information exactly the same way as a living brain, it would generate the same conscious experiences," says Seth. Such a machine might allow your consciousness to survive death. But it would still not know what it is like to be a bat.
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