Neurobiologist works to localize memory;
research could lead to better understanding of the human brain

mushroom bodies (brown) in 3-D in the context of the rest of fly brain Karlheinz Rein, Malte Zöckler, Michael T. Mader, Cornelia Grübel, and Martin Heisenberg "The Drosophila Standard Brain," Current Biology 2002 12: 227-231.

Chasing a memory in the brain of a fruit fly is frustrating, tedious work. Each new discovery invariably yields many more questions. But Troy Zars is patient. Since 2000, Zars, an assistant professor of Biological Sciences at the University of Missouri-Columbia, has discovered several principles about memory formation in the brain of Drosophila melanogaster, the scientific term for the fruit fly, that could help scientists’ understanding of the human brain.

Neurobiologists once thought that the "mushroom body," an "L"-shaped structure in the insect brain, was the seat of all higher-order functions, such as memory formation. Years of work in a renowned German research laboratory helped Zars and his colleagues determine that memory can be stored in a defined set of cells of the fly’s brain, including the mushroom bodies, but that there is no single memory center. In other words, Zars’ research team determined that different brain regions, or structures, house memories for different learning tasks.

To determine the site of memory formation, Zars’ team manipulated the ability to strengthen nerve-cell connections, also known as plasticity, in parts of the fly’s brain by changing the fly’s genetic composition in those different brain regions. The team then tested the fly’s ability to form memories. For example, one test measured the preference flies displayed for an odor paired with a weak electric shock. When flies learned and remembered, it was possible to localize the site of memory formation by knowing where the previous genetic manipulations were induced inside the brain.

Despite major medical and psychiatric advancements of the past century, scientists know very little about how the human brain, as an integrated set of neural circuits, controls memory. Indeed, a major goal of neuroscience is to discover the location of memory-forming structures within a brain. This general goal motivates Zars to learn as much as possible about the brain of simpler systems, as in Drosophila. Zars works with Drosophila because they are a well-established genetic model, have a relatively less complex brain than the mouse or human (250,000 neurons vs. 100 billion neurons), and have a broad repertoire of behaviors.

"Why is this research important?" Zars asks rhetorically. "To ultimately understand complex neural systems, we must first be able to understand a simple brain."

More on Zars findings can be found in the journals Learning and Memory, Science and Neuron.

2002

Additional links:

Troy Zars 
Division of Biological Sciences

Flybrain: http://www.flybrain.org

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