Focus on Aging: Understanding Brain Plasticity

Credit: Michelle Carroll

Sara Burke has a vivid memory of how neuroscience first drew her attention. She was a second-year undergraduate student at the University of Oregon, Eugene, sitting in an introductory psychology class. Neurobiologist Richard Marrocco was describing how Alzheimer's disease, though typically thought of as a memory disorder, also affects attention. "He was just talking about how different systems interact and that nothing really declines in a vacuum," she says. "It was just kind of an instant love of the field that has lasted since."

"Her work will be considered 'classic' or foundational, something every graduate student wants to achieve but only very unique individuals are able to accomplish." -- Carol Barnes

Today, Burke is a postdoctoral research associate working with Carol Barnes, who leads the Evelyn F. McKnight Brain Institute and the University of Arizona Research Laboratories Division of Neural Systems, Memory and Aging in Tucson. Burke's focus is on understanding how normal aging affects the natural plasticity of neuronal networks and, ultimately, behavior. "Even if you are one of the lucky ones and you manage to age quite successfully, there are still changes that occur in your brain throughout the life span," and these changes will affect neural networks supporting cognitive abilities, she says. "What I really would like to see happen is behavioral interventions that can be used to improve cognitive outcomes."

An enduring passion

A year after her revelation, Burke was in Marrocco's lab, injecting rats with agents that modify the activity of dopamine receptors to see whether they could improve the animals' reflexive ability to direct attention to visual targets. The work led to an undergraduate honor's thesis, but the University of Oregon didn't yet offer a neuroscience major, so Burke tailored her studies, she says, "to get the coursework that I thought I would need to go on and be able to be successful in graduate school."

Focus on Aging Research

Researchers in many different disciplines are looking at how to make our aging population stay healthy for longer. Throughout the month of May, Science Careers will publish profiles of scientists studying healthy aging from the perspective of genetics, sociology and psychology, engineering, and neurology.

After finishing her bachelor's degree (with a major in psychology, a minor in chemistry, and command of much of the university's biology curriculum), Burke stayed on in Marrocco's laboratory for a M.Sc. degree, exploring rats' ability to direct their attention voluntarily and making a pioneering contribution to that field, according to Marrocco. One year later, she took a position as a research associate at Oregon Health & Science University's Neurological Sciences Institute (now the OHSU Brain Institute) in Portland to study how high blood pressure and hormone status affect visual adaptation over the life span.

Aging and cognition

Burke then contacted Barnes about doing a Ph.D. in her aging and memory lab. "While I do get quite a few people applying to my lab … very few have a long-standing passion to understand the aging brain," Barnes writes in an e-mail to Science Careers. Burke's passion and strong curriculum vitae won her an interview; her poised, articulate, and focused attitude earned her admission, Barnes says.

In the Barnes lab, Burke worked to understand how the ability to recognize familiar objects changes over the life span. She compared how young and old rats (the equivalent of 75 human years) respond to new and familiar objects. "Rats and many other animals are drawn to something that's novel, so if you present them with a novel object and a familiar object, they're going to just naturally spend more time exploring the novel object," she says. As the rats investigated the objects, Burke recorded the activity of dozens of neurons in the perirhinal cortex.

Barnes calls Burke's contributions to the field "critical." "She, with outstanding experimental design, was able to clarify a number of misconceptions" about why older humans and animals have object-recognition memory deficits. She showed that old rats are not as good at discriminating novelty as their younger counterparts, not because they forget having seen a familiar object but because they summon up false memories of unknown objects. Burke went on to describe a type of cellular activity in the perirhinal cortex that changed with age and that potentially could explain age-associated object-recognition deficits. "Her work will be considered 'classic' or foundational, something every graduate student wants to achieve but only very unique individuals are able to accomplish," Barnes says.

One of the work's chief challenges, Burke says, was working with old rats. One day they were healthy and the next "the rats had a stroke or their health turns for the worse." Another challenge was analyzing the data -- but she got help from her husband, Andrew Maurer, whom she met while he was doing a Ph.D. in a collaborating lab.

Burke earned her Ph.D. in neuroscience (with a minor in pharmacology) in 2009. She stayed on in the Barnes lab for her postdoc, studying the use of memory in complex tasks, such as learning, and its interaction with attention over the life span. In collaboration with Adam Gazzaley at the University of California, San Francisco, she is testing how distractions affect the ability of old monkeys to perform memory exercises. She discovered in monkeys -- and Gazzaley saw in humans -- that those who are older are just as capable of performing the exercises as those who are younger, provided the memory demand is low and they are allowed to concentrate. "Older adults are not able to suppress exogenous stimuli that are irrelevant for performance," Burke says. This summer, Burke says, she will "be doing structural MRI with the animals to see if there is any sort of anatomical changes that might be occurring in the brain that we can correlate with the behavior."

Credit: Andrew Maurer
Sara Burke is hailed by her colleagues as a good mentor and scientific communicator

Life impacts

Burke anticipates that her research will eventually impact well-being in those aging normally. "There's going to be a demographic shift towards an older and older population, ... so just for well-being and also for health care costs, it's critical to understand what's changing cognitively and then find potential therapeutic targets or even behavioral interventions that can help people age more successfully."

Burke is already having an impact on the junior researchers she mentors. She "was always around to help guide me through both life as a graduate student as well as scientific issues such as experimental design, execution, and interpretation," Lan Hoang, a former master's student who stayed in the lab as an assistant staff scientist, writes in an e-mail to Science Careers. "Sara has a 'can-do' attitude that never falters. Even when an experiment fails or yields an unexpected and seemingly incomprehensible result, Sara remains determined and excited."

Burke and Maurer have found a way to balance personal and professional life. Today, Maurer is also a postdoc in the Barnes lab. "Now [that] we both work for Carol, we actually share [an] office, which is very convenient," Burke says, adding that they help each other a lot in their work. The couple have shared authorship on several papers. They have a 1-year-old son; Burke and her husband each stay at home with him 1 day a week, catching up on work during evenings and weekends.

"She'll be a hot commodity when she decides to go on the job market," Barnes says. Burke plans to apply for a career development award from the U.S. National Institutes of Health in a few years' time to initiate her transition to independence. "At that time, both my husband and I will be looking for positions together. Because we understand that this might be difficult, both of us have been focusing on having a broad" and different "set of skills," she says. Having a family and a career is difficult, but Barnes is confident in Burke's future: "She is a rising young star, and I see no reason for her not to accomplish all the goals she sets for herself."

Elisabeth Pain is Contributing Editor for Europe.

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