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January 26, 2012

Research Notes

Age-related differences in reward responses found

In a paper published in the Jan. 16 Proceedings of the National Academy of Science, Pitt researchers report that teenagers are more susceptible to developing disorders like addiction and depression.

Neuroscience faculty member Bita Moghaddam and co-author David Sturman, a MD/PhD student in Pitt’s medical scientist training program, compared the brain activity of adolescent and adult rats involved in a task in which the rats anticipated a reward.

The researchers found increased brain cell activity in the adolescent rats’ brains in an unusual area: the dorsal striatum (DS) — a site commonly associated with habit formation, decision-making and motivated learning. The adult rats’ DS areas, on the other hand, did not become activated by an anticipated reward.

“The brain region traditionally associated with reward and motivation, called the nucleus accumbens, was activated similarly in adults and adolescents,” said Moghaddam. “But the unique sensitivity of adolescent DS to reward anticipation indicates that, in this age group, reward can tap directly into a brain region that is critical for learning and habit formation.”

The Pitt team used a “behavioral clamping” method to study whether the brains of adolescents process the same behavior differently than adults. They implanted electrodes into different regions of adolescent and adult rats’ brains to study both individual neurons’ reactions and the sum of the neurons’ (or population) activity.

Even though the rats’ behavior was the same, the researchers observed age-related differences in neural response that were especially dramatic in the DS during reward anticipation. This shows that not only is reward expectancy processed differently in an adolescent brain, but also it can affect brain regions directly responsible for decision-making and action selection.

“Adolescence is a time when the symptoms of most mental illnesses — such as schizophrenia and bipolar and eating disorders — are first manifested, so we believe that this is a critical period for preventing these illnesses,” Moghaddam said. “A better understanding of how the adolescent brain processes reward and decision-making is critical for understanding the basis of these vulnerabilities and designing prevention strategies.”

The researchers plan to continue to compare adolescent and adult behavior, especially as it relates to stimulants — such as amphetamines — and their influence on brain activity.

The National Institute of Mental Health funded this project.

Shell patterns reveal neural evolution

Through mathematical equations and simulations, researchers at Pitt and the University of California-Berkeley have generated a model of the pigmentation patterns of mollusk shells, based on 19 different species of the predatory sea snail Conus.

Determining the evolution of such patterns could aid in the understanding of ancient nervous systems.

Project co-investigator G. Bard Ermentrout said, “There is no evolutionary record of nervous systems, but what you’re seeing on the surface of seashells is a space-time record, like the recording of brain-wave activity in an electroencephalogram (EEG).”

Ermentrout is a Distinguished University Professor of Computational Biology and a faculty member in the Department of Mathematics.

Seashells differ substantially among the closely related Conus species, and the complexity of the patterns makes it difficult to properly characterize their similarities and differences. It also has proven difficult to describe the evolution of pigmentation patterns or to draw inferences about how natural selection might affect them.

In a paper published in the Jan. 3 issue of Proceedings of the National Academy of Science Online, Ermentrout and  colleagues attempted to resolve this problem by combining models based on natural evolutionary relationships with a realistic developmental model that can generate pigmentation patterns of the shells of the various Conus species.

In order for UC-Berkeley scientists to create simulations, Ermentrout and his collaborators developed equations and a neural model for the formation of the pigmentation patterns on shell surfaces. With the equations in hand, the UC-Berkeley team used a computer to simulate the patterns on the shells, hand-fitting the parameters to create a basic model for the patterns of a given species.

The results of this study have allowed the researchers to estimate the shell pigmentation patterns of ancestral species; identify lineages in which one or more parameters have evolved rapidly, and measure the degree to which different parameters correlate with the evolutionary development and history of the organisms. Since the parameters are telling the researchers something about the circuitry of the mollusks’ nervous system, this is an indirect way to study the evolution of a simple nervous system.

“We’ve found that some aspects of the nervous system have remained quite stable over time, while there is a rapid evolution of other portions,” said Ermentrout. “In the future, we hope to use similar ideas to understand other pattern-forming systems that are controlled by the nervous system. For instance, we would really like to develop models for some of the cephalopods like the cuttlefish and the octopus, which are able to change patterns on their skin in an instant.”

The National Science Foundation provided funding for this research. The paper is posted at

What color is your galaxy?

A team of Pitt astronomers reports that the most accurate determination of the color of the Milky Way Galaxy is “a very pure white, almost mirroring a fresh spring snowfall.” Physics and astronomy faculty member Jeffrey Newman and physics PhD student Timothy Licquia described their findings at a meeting of the American Astronomical Society.

While color is among the most important galactic properties astronomers study, it has been difficult to determine the measurement for the Milky Way.

Because the solar system is located well within the galaxy, clouds of gas and dust obscure all but the closest regions of the galaxy from view, preventing researchers from getting the big picture.

Newman explained, “The problem is similar to determining the overall color of the Earth, when you’re only able to tell what Pennsylvania looks like.”

To circumvent this problem, Newman and Licquia set out to determine the Milky Way’s color by using images of more distant galaxies that can be viewed more clearly. These galaxies were observed by the Sloan Digital Sky Survey (SDSS), which measured the detailed properties of nearly a million galaxies and obtained color images of roughly one-quarter of the sky.

The Pitt team identified galaxies similar to the Milky Way in properties that were able to be determined — specifically, their total amount of stars and the rate at which they are creating new stars, which are both related to the brightness and color of a galaxy. The Milky Way, the Pitt researchers realized, should then fall somewhere within the range of colors of these matching objects.

“Thanks to SDSS, the large, uniform sample needed to select Milky Way analogs already existed. We just needed to think of the idea for the project, and it was possible,” said Newman.

The new color measurement is allowing Pitt researchers to better understand the development of the Milky Way and how it is related to other objects astronomers observe.

Astronomers divide most galaxies into two broad categories based on their colors: relatively red galaxies that rarely form new stars, and blue galaxies where stars are still being born. The new measurements place the Milky Way near the division between the two classes.

This adds to the evidence that although the Milky Way is still producing stars, it is “on its way out,” according to Newman.

“A few billion years from now, our galaxy will be a much more boring place, full of middle-aged stars slowly using up their fuel and dying off, but without any new ones to take their place,” Newman said.

Funding for this project was provided by the National Science Foundation.


The University Times Research Notes column reports on funding awarded to Pitt researchers as well as findings arising from University research.

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