Johns Hopkins Gazette: June 9, 1997

Gallagher Ably
Filling Olton's

Emil Venere
News and Information
When David Olton died three years ago, the Psychology Department lost a respected neuroscientist, an expert on the biological basis of learning and how aging affects memory.

The department also lost a valuable teacher and mentor. Olton, who died of pancreatic cancer at the age of 51, headed the department's behavioral biology program, in which he advised scores of undergraduates each year.

It wasn't going to be easy to fill his shoes.

"There was a very intensive national search," said psychology Professor Gregory Ball, a member of the search committee. "It took us two years, and we had close to 200 applicants."

Michela Gallagher, an internationally known neuroscientist from the University of North Carolina, has now been appointed to the vacant faculty position.

Gallagher is a behavioral neuroscientist; she specializes in research on aging, learning, memory and attention, focusing on brain structures known as the amygdala and hippocampus.

"We've always had a tradition of looking at the mechanisms of learning and memory," said psychology Professor Randy Nelson. "It was important for our program to get someone world-class to train our graduate and undergraduate students in this important area."

Olton was a contemporary of Gallagher's, and he conducted similar research on learning in animals.

"I do feel that I fit that niche," she said. The most recent doctoral candidate to study under Gallagher had learned neuroscience from Olton while an undergrad at Hopkins, she said.

Gallagher, who has been at the University of North Carolina for 17 years, has recently challenged a long-held misconception about aging and declining brain function.

"A common myth in aging is that you lose large numbers of brain cells," Gallagher said. "That myth was derived from early studies of the brains of patients with Alzheimer's disease."

The disease is characterized by the massive loss of neurons in certain vital regions of the brain, including the hippocampus.

Scientists had thought that the same sort of degeneration seen in Alzheimer's patients also was going on in normal aging brains.

Not true, Gallagher discovered. She found that there was no significant loss of neurons in the hippocampus of a normal aging brain. Instead, older neurons do not function as well as those of younger brains. For example, they are not as good at communicating with one another, a process known as signal transduction. They also are not as capable of changing their properties to perform new tasks--an ability called brain plasticity--which is important for learning.

"It's an interesting observation because it calls for different approaches to treatment or interventions in aging," Gallagher said. "If neurons aren't lost but are functionally altered, you might take very different approaches. It also makes aging look like quite a distinctive picture from Alzheimer's. In some ways it highlights the pathology of Alzheimer's disease as not characteristic of normal, healthy aging."

Gallagher is editor in chief of Behavioral Neuroscience, a journal published by the American Psychological Association, and she is a fellow of the American Association for the Advancement of Science. She also belongs to a committee at the National Institutes of Health that oversees clinical research on Alzheimer's disease.

She heads a research program to study aging in animals, primarily rats, to learn more about aging in human brains.

Gallagher is particularly interested in the hippocampus and amygdala, which are located in the front of the brain. Scientists have learned that the seahorse-shaped hippocampus is critical for memory in humans.

"There is a very famous patient who had surgery for intractable epilepsy," Gallagher said. The hippocampus was surgically removed to control the epilepsy.

"After the surgery he had the inability to form new memories, but he didn't forget who he was or events in his childhood," she said.

That finding, and further research with animals, suggested that storing and retrieving memories requires a specialized system in the brain that includes the hippo-campus. It also pointed to a role for that system in the memory problems of aging.

"The elderly can reminisce well about their childhood. Their memory complaints have more to do with current information. Like, 'I can't remember this person's name, and I met him just yesterday,' " she said.

That is because neurons in the aging hippocampus don't work as well as they used to. So, to a lesser extent than the epilepsy patient, aging people do not have the full use of that brain structure.

The amygdala is known for its role not in memory but in emotion and learning. In fact, emotion can have a profound effect on learning in animals and people, said Gallagher, who has studied the amygdala since her days in graduate school, at the University of Vermont, where she earned her doctorate in psychology.

"We can readily acquire fear in situations that might be normally innocuous if something bad happened there," she said. "If an animal has some aversive event in a particular environment, it will develop a fear response in that environment."

It's called "fear conditioning."

On the other hand, if something good happens in a specific environment, an animal may develop a preference for that place.

Damage to the amygdala seems to impair an animal's ability to make such associations, a type of learning that often is vital for survival. Gallagher's recent research suggests that the structure serves an even broader role in adaptive behavior.

"For example, when driving a customary route, you probably pay little attention to familiar landmarks along the way but are more likely to notice some feature of the environment that has changed," she said. "The surprise you experience engages your attention to revise the associations you previously held. The amygdala is also important for this function."

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