Can drugs drill holes in your brain?

The idea of drugs tunneling their way through the brain, worms to the mind’s apple, is a frequent metaphor I hear. I wrote on the topic for Discovery’s Curiosity and resurfaced it to prepare material for drug education talks with high schoolers. Here’s a simple look back at the common question, which never fails to remind me just how complex, yet undeniably vulnerable, our brains are:

Girls' and boys' brains: How different are they?

When my son was a toddler, his best friend, a girl, gave him a sparkling dancing Katrina doll for a birthday present. He'd apparently admired the doll at her house, but once he got it he never played with it – until the day I found him chasing his little brother around with the doll, which he'd managed to twist into the shape of a gun.

Boys will be boys? Proof that gender differences are hardwired? Not so fast. Like most parents, I have just as many tales illustrating the influence of nurture on my son's behavior. At preschool one day, as he was playing dress up with two girlfriends, he donned a scarlet tutu. Within a minute an older, cooler boy guffawed, "Boys don't wear dresses!" He never put on girl clothes again.

Brain's synaptic pruning continues into your 20s

Brain's synaptic pruning continues into your 20s

16:07 17 August 2011 by Wendy Zukerman and Andrew Purcell
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The synaptic pruning that helps sculpt the adolescent brain into its adult form continues to weed out weak neural connections throughout our 20s. The surprise finding could have implications for our understanding of schizophrenia, a psychological disorder which often appears in early adulthood.

As children, we overproduce the connections – synapses – between brain cells. During puberty the body carries out a kind of topiary, snipping away some synapses while allowing others to strengthen. Over a few years, the number of synapses roughly halves, and the adult brain emerges.

Or so we thought. Pasko Rakic at Yale University and colleagues at the University of Zagreb, Croatia, and the VU University Medical Center in Amsterdam, the Netherlands, have now found that the brains of adults in their 20s are still subject to synaptic pruning.

Rakic's team analysed post-mortem tissue from a brain region called the prefrontal cortex (PFC) in 32 people aged between 1 week old and 91 years. Specifically, they calculated the density of dendritic spines – the tiny projections that protrude from the neuron's long dendrites, each of which facilitates communication with other neurons through a synapse.

As expected, Rakic's team found that spine density increased rapidly during infancy, reaching a peak before the 9th birthday. It then began to fall away as pruning began. Intriguingly, though, spine density did not plateau after adolescence, as might have been expected, but continued to fall gradually until the late 20s.

Rakic says the result could be good news for those hoping to gain new skills in their third decade. The period of pruning is associated with a heightened ability to learn – whether that is in picking up language skills or understanding new concepts, he says. "You should not give up learning just because you're in your 20s – it isn't too late," he says.

The finding also has implications for our understanding of some psychiatric disorders. The PFC is thought to be particularly relevant to late-onset disorders such as schizophrenia, says Rakic, but it is unclear whether such disorders are triggered by developmental or degenerative processes. The new finding is likely to give weight to the idea that schizophrenia emerges as a result of late brain development.

"I'm sure that for many people schizophrenia has a strong developmental component," says Sabine Bahn, who researches schizophrenia at the University of Cambridge – although she adds that some cases will likely have a degenerative component.

Elena Bagley at the University of Sydney, Australia, agrees with the conclusion. It is possible that the prefrontal cortex "is susceptible for longer to disorders and disease that result from abnormal pruning", she says. Such pruning may also contribute to memory loss and dementia, she adds.

Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1105108108

Brain Scan predicts Pop Hits?

Is there some kind of neural signature that indicates what will ultimately become popular and obsessed over, and what will flop?

Scientists monitor the brains of teens listening to songs and find the breakout hits tend to share certain neural signatures

Genetic Influence on Impact on Memory.

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Observations

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Refuse to learn from experience? Thank your genes
By Katherine Harmon | April 19, 2011 | 10

Some people are incurable contrarians or imperturbable logicians. But most of us, whether we like it or not, allow other people’s opinions and advice to color our own experiences and opinions. Have you found that restaurant to really be as good as people say it is?

New findings suggests that a person’s willingness to coolly consider the facts gleaned from their own experience—apart from others’ previous verbal suggestions—might be based in large part on genetics.

It has been known and frequently demonstrated that "people will distort what they experience to be perceived as more consistent with what they thought already," Michael Frank, of the Brown Institute for Brain Science at Brown University, and a collaborator in the new research, said in a prepared statement. Even researchers can fall prey to confirmation bias, thinking they have discovered what they actually had expected to find in the noise of data.

So, why do we often struggle to accept our own impressions if they contradict what we’ve been told to expect? The disconnect occurs in part because these two types of information, the abstract and the experiential, are processed in different parts of the brain. Advice ("go to that Italian restaurant") is filtered, along with other higher-level cognition, in the prefrontal cortex. Experience ("that Italian restaurant is usually mediocre"), on the other hand, is lodged in a more primitive region of the brain, the striatum.

Although perhaps we should be more inclined to stick with what our gut (or tastebuds) has learned from personal experience, most people tend to lean on what their prefrontal cortex—i.e. outside instruction—has to say for more time than they rationally should.

"Maintaining instructions in the prefrontal cortex changes the way that the striatum works," Bradley Doll, a researcher at Brown, said in a prepared statement. "It biases what people learn about the contingencies they are actually experiencing," noted Doll, who coauthored a new paper detailing the results, which published online April 19 in The Journal of Neuroscience.

People’s willingness to let advice color their experience hinges at least in part on the neurotransmitter dopamine, which is associated with pleasure, reward and learning. The researchers pinpointed one gene in particular, COMT, that seems to play a role in a person’s inclination to learn from his or her own experiences. Individuals in the study with different alleles of this gene had differing propensities to be biased by outside advice in interpreting their own experiences.

Frank, Doll and colleague Kent Hutchinson tested more than 70 adults on a computer-based learning program. Subjects had to learn which symbols were most likely to be classified as the "correct" answer. The correlation was based on probability, rather than strict correlation, creating a gray area in which subjects had to weigh their past experiences with each symbol. In some tests, people were given advice about which symbols were correct most often—but this advice sometimes proved to be incorrect.

People with an exceptional ability to spot inaccurate instructions and start making decisions using their own experience tended to have the Val/Val version of the gene, whereas those who needed "greater confidence" that their experience was telling them to jettison earlier advice were more likely to have the Met allele.

Overall, the researchers concluded, "these findings suggest that the striatal learning process is modulated by prior expectations, and that the resulting associative weights cannot be easily ‘undone’ after the prior is rejected." So that might mean you have to order many bowls of substandard pasta before you finally admit to yourself that a much-lauded Italian restaurant isn’t actually all that great.

Of course, it’s certainly easier—and less painful—to learn to avoid a hot plate by being told to do so, and we’ve likely evolved to take this into account, prizing the prefrontal cortex’s retained instructions. "This phenomenon of confirmation bias might actually just be a byproduct of a system that tries to be more efficient with the learning process," Frank said.

But the human mind is rarely satisfied with simple instruction, as instruction—and advice—often turn out to be wrong. And what’s a few burnt fingertips in the grand scheme of independent thought?

Tips For Brain Boosting

Need to learn a lot of material fast and perform well when it counts? Two new studies suggest easy ways to speed up learning and ease anxiety before a test.more