A better look

Despite the fact that scientists are able to look inside the brain using a variety of live imaging techniques, their ability to visualize individual neurons in living animals is very limited. Thus our understanding of what is really going on during learning and disease, for example, is also incomplete. A new technique developed by Dr. Mark Schnitzer at Stanford University, however, may change that, by letting scientists look at individual neurons in areas of the brain not accessible by traditional imaging tools.

Known as time-lapse microsendoscopy, this new technique allowed Dr. Schnitzer’s group to observe the same population of neurons in the hippocampus, a brain area involved in learning and memory, over the course of seven weeks in live animals. While the study focused on the effects of gliomas, a type of tumor that originates in the brain, the technique could also be used to monitor changes associated with diseases such as cancer, stroke, or Parkinson’s disease.

While microendoscopy is currently being used to diagnose certain forms of cancer, this is the first reported use of microendoscopy over a long period of time. This unique development may help scientists to understand how diseases in the brain and other organs progress, which may ultimately lead to better therapies.

Find out more about how time-lapse microendoscopy in the brain works from this interview with Dr. Schnitzer.

Image courtesy of Nicolas P. Rougier.

Merry Melody

Music is all around us. Whether you’re listening to one of Mozart’s classic concertos or to William Hung’s rendition of “She Bangs”, music has a tremendous ability to heighten our emotions. When it comes to pleasure, a team of researchers led by Dr. Robert Zatorre at McGill University has learned that listening to music causes the release of dopamine, one of the brain’s “feel good” chemicals, from key areas involved in reward and learning.

While scientists already knew that these brain areas were activated in response to music, this study is the first to show that dopamine is involved in how we process musical information. To account for differences in musical taste, researchers asked participants to bring in their own pleasurable music. (Samples are available on Dr. Zatorre’s website, and a list of the participants’ selections can be found in Table S1 of another study by this group.) Using brain imaging, lead author Dr. Valorie Salimpoor was able to observe peaks in dopamine release at the same time that participants reported experiencing intense pleasure. To get a better idea of when and where this dopamine was being released, she and her team used a second imaging technique known as functional magnetic resonance imaging, or fMRI. What they found, she says, was unexpected, but extremely interesting.

They noticed that “before people experience their peak pleasure to music, during an anticipation and build-up period, they’re also releasing dopamine, but in an entirely different region.” When participants were in the heights of musical rapture, dopamine release was most intense in the nucleus accumbens, an area that is highly connected to brain regions that process emotion. However, prior to this climax, dopamine release occurred mostly in the caudate, which is connected to areas involved in learning, expectation, and complex thinking. Because participants knew that their favorite parts of the music were coming up, their brains anticipated this reward by releasing dopamine.

Interestingly, a similar phenomenon occurs after repeated exposure to cocaine, a drug that also acts on the dopamine system. Once an animal has learned to associate certain stimuli with cocaine, it experiences two peaks in dopamine release: the first in anticipation of the drug and the second once it gets its fix. Scientists think that this anticipatory dopamine may serve to focus our attention on rewards, while the “high” we later experience may then motivate us to seek out these rewards again and again.

What the study suggests is that the reason music has such a powerful hold on us – why we spend exorbitant amounts of money on iPods and concert tickets – is that, as Dr. Salimpoor explains, music “works on the brain’s most powerful reinforcement and addiction circuit.” This is the first time that scientists have shown that dopamine is released in response to aesthetic stimuli, and Dr. Salimpoor is now working on deciphering how our brains determine if a novel piece of music is pleasurable or not.

Given the importance of music across cultures, this study sheds new light on why an appreciation for music has been conserved in humans despite the fact that it lacks an obvious evolutionary role. Music allows us to experience intense pleasure (or pain). It can transport us through time and space, letting us relive the past or imagine the future, if only for a moment. And that, as Andy Dufresne would say, is the beauty of music.


To find out more about this study, please visit Nature Neuroscience. If you are interested in learning more about the way we process music and its relation to language, listen to RadioLab's program Musical Language.

Image courtesy of Valorie Salimpoor and Peter Finnie.

Penguin troubles

Tagging animals is a practice used widely by scientists, farmers, and the food industry to identify animals in a group. While tagging makes it much easier to track individuals, attaching a piece of plastic or metal to an animal's ear or wing, for example, is bound to have an effect on behavior, and perhaps even on survival. In the field of penguin research, this has been a much-contested issue, as there are conflicting reports on the damaging effects of tagging penguins with flipper bands going back to the 1970s.

Led by Dr. Yvon Le Maho at the French National Center for Scientific Research, scientists showed that, over the course of ten years, king penguins with flipper bands (pictured here) had fewer chicks and a lower rate of survival than their unbanded counterparts. Though they could not test this directly, they think that these effects are likely the result of significant drag caused by flipper bands. This drag slows penguins down, making them more vulnerable to predators and less efficient at catching prey. Consistent with this idea, the team showed that banded penguins took longer to return home to breed and to feed their chicks, putting them in a reproductive quagmire.

The study further shows that banded penguins are more sensitive to climate conditions. In extremely good or bad years, banded and non-banded penguins fared similarly, but under 'normal' conditions there were significant differences. While this is not readily obvious, it has to do with the relative amount of resources available. Imagine you are fighting for the only slice of bread left. You are smarter and faster than the poor souls next to you, so you'll get the grub. Sadly, eating said slice will not really help you to survive the week, as it's not enough to meet your body's needs. Bye, bye for you. Conversely, if there are 100 slices of bread, you will eat your fill and leave some behind for all the rest to enjoy. However, if there are 20 slices around, only you and those that are almost as smart and as fast as you will get to eat. The rest will perish. This is essentially the predicament in which banded penguins find themselves. They cannot outcompete their non-banded friends, and are therefore at a disadvantage.

The results of this study have far-reaching repercussions. Penguins are often used to study the effects of climate change on marine ecosystems. However, most of these studies used flipper bands to track individual penguins, so the results may be biased. Other types of tags, such as the small implanted transponder tags used in this study, may be less harmful to animals and yield more reliable results. Because most scientists use tags to identify animals, these results are relevant to other fields of research. Therefore, it is important not only to develop less invasive technologies, but also to keep an open discussion on the methods we use to study animals around us.


For more information on this study, please visit Nature.com

I am the decider...for now anyway

Imagine you're a guy at a club in the dead of winter. Sexy ladies with stunning eyes are looking in your direction, each making a move. You look around. Perhaps they're smiling at a friend who's just arrived? No, they're looking at you! You can't believe your luck! Back in the summer, it was a completely different story. You had to do all the work. Could there be a Sadie Hawkins theme here? You decide to try your luck again the following night. Nope. Ladies all around are fighting for you! Amazing! But you can't help but wonder what is going on...usually it's the other way around...

When researchers at Yale University started looking at mating patterns in African butterflies (pictured here) what they observed was very much like our stupefied guy's situation. They found that the temperature to which butterflies were exposed as caterpillars dictated their courting behavior. When butterflies developed during the warm season, then it was up to the males to

make the first move, and the females could play hard to get. In the cold season, however, it was the complete opposite. Females had to throw their inhibitions to the wind and make their move on the male of their liking.

Why does this happen? Typically speaking, the gender that chooses has more to lose by accepting the advances of a less than ideal partner. Another way to think about this is that the gender that chooses has more to invest. Think about the relative size (and number) of sperm and egg cells. In humans, an egg cell is HUGE compared to a sperm cell. Moreover, a female will produce one egg, maybe two, each month, while a male lets loose millions of sperm each time he has a happy ending. Therefore, it is to the female's benefit to choose wisely, lest she be up the reproductive creek without a helping paddle. As Matt Ridley so wisely put it in the Red Queen, "a female...gives birth to a gigantic baby that has been nurtured inside her for a long time; a male can become a father in seconds. Women cannot increase their fecundity by taking more [partners]; men can."

This is very similar to what happens in African butterflies, except that the amount of parental investment between the sexes changes from one season to the next. In the warm season, when the females choose, the females stand to lose more, while in the cold season, it is the reverse. A cold season male gives his lady friend a spermatophore, a capsule filled with nutrients, a trust fund so to speak, that helps her to live longer and to lay more eggs. In the warm season, however, there are plenty of nutrients to go around, and as Dr. Antónia Monteiro, who led the study at Yale, explains, "females don't need to gather [food] from males and males invest only in cheap sperm. Male's don't need to be choosy about picking a female because they don't suffer a cost to mating [repeatedly]. Females, however, will need to make the right mating decision because they will lay eggs right after mating [in the warm season] and if they mate with a sub-optimal male, they will have infertile or poor quality offspring."

So how does a choosing male or female butterfly know if her potential mate is worth the risk? Once again, it's all about the eyes. Well, the eyespots in this case. In the picture above, notice the rings on the butterflies' wings. These are commonly known as eyespots, and the white center as the pupil. What Dr. Monteiro's group found was that regardless of who was doing the choosing, both males and females preferred to get down with someone with who had a nice, visible pupil. Conversely, those doing the courting had large pupils to alert potential mates that they were the cream of the crop. Because both males and females use eyespots as a means to attract the opposite sex, these ornaments have been preserved across genders, suggesting that sexual role reversal may affect a species' physical traits. This will be especially important for species with short life spans, like butterflies.

This study, published in the current issue of Science magazine, sheds new light on mating behavior in insects and challenges the age-old notion that a lady never makes the first move.

Picture courtesy of William Piel and Antónia Monteiro. To find out more about this study, please visit the Science magazine website.