If Hopkins undergraduate Serena J. Gondek had a mild case of nerves before a speaking engagement last week in Minneapolis, it was certainly understandable.

The 21-year-old biomedical engineering major had to describe her groundbreaking brain research to a highly educated audience of physicians and other experts in disorders of the nervous system.

Serena J. Gondek, a biomedical engineering major, has finished up her junior year with a flourish. Last week in Minneapolis she presented her groundbreaking brain research to an august gathering of experts in the field and found herself being interviewed by CNN and the BBC.

Using electrodes implanted on the human cortex, Gondek had located the part of the brain that appears to process sounds while people sleep. This site, in the frontal lobe, may be part of a vigilance system that rouses a mother when her baby cries but lets the woman sleep when a truck rumbles by.

Gondek had been chosen to give an oral presentation on her findings at the annual meeting of the American Academy of Neurology, billed as the world's largest gathering of neurologists and neuroscience professionals.

Her 10-minute talk attracted more than 100 of these professionals, some of whom did not realize the speaker was only in her junior year at Hopkins. "They were addressing me as 'Dr. Gondek,' " she recalled later, with a laugh. "I didn't correct them. I let it slide."

Administrators at the academy said it was unusual for an undergraduate to be chosen to make an oral research presentation at the event.

Although she was a bit jittery before her program, the talk itself went smoothly, she said, followed by a lively round of questions from the audience. Also in the room were her mother and father, who had driven in from their home in the Chicago suburb of Oak Brook. "I think my parents were more nervous than I was," Gondek said. "My dad videotaped the talk."

Her research also put Gondek and Gregory L. Krauss, the faculty member who supervised her experiments, in the news. Their work was covered by CNN, The Sun, the BBC and other media.

"It was really exciting," Gondek said. "It was nice that they recognized me not just as a young scientist but because the science itself was important."

Previous studies on hearing during sleep had relied on electrodes attached to a subject's shaved scalp. Gondek's experiment is believed to be the first of its type to use electrodes implanted directly on the brain, a technique that yields far more precise information about which parts are activated by sounds during sleep.

Krauss, an assistant professor of neurology at the School of Medicine, is co-author of the research paper, titled "How do we hear while we sleep?" He was in the audience during Gondek's talk last week.

"It is controversial how we monitor our environment while we sleep," Krauss said before the conference. "It's a pretty big part of our lives, but sleep is poorly understood. The main thing that Serena did was to show where on the cortex we hear while we sleep. She did a terrific job, particularly in the brain mapping."

Gondek is the second Hopkins undergraduate in recent months to present research findings at a major medical conference, in collaboration with Krauss. At a meeting of the American Epilepsy Society in December 1997, R. Colin Carter, a 22-year-old senior from Scotch Plains, N.J., reported on epilepsy patients who are at risk for driving accidents.

"Undergraduates are great for these kinds of projects because they're very enthusiastic," said Krauss, "and they work very hard."

Hopkins professors often encourage undergraduates to take part in high-level scientific studies. "That's why I really looked forward to coming to Hopkins," said Gondek. "It's been as easy as knocking on a few doors to become involved in research projects, even during my freshman year."

Her sleep research was supported by a General Electric Foundation Undergraduate Engineering Research Stipend.

For her experiment, Gondek obtained the cooperation of five epileptic patients who had had electrode grids implanted directly on their brains prior to surgery to curtail seizures.

Special plugs placed by Gondek in the patients' ears blocked out room noise but allowed the patients to hear sequences of two tones emitted by Gondek's equipment, one tone pitched at 500 hertz, the other at 1,000. She played various tone patterns while the patients were awake, during light sleep and during deep sleep. The electrodes detected which portions of the brain were activated. Gondek analyzed the results and mapped them onto MRI and CT scans made of the patients' brains.

"We found that during waking, only areas around primary auditory cortex are activated by the tones," she said. "Then, during light and deep sleep, you find not only primary auditory activation, but the frontal lobe also responds."

The frontal lobe is believed to play a key role in vigilance functions, such as screening new stimuli and preparing the body to react. During sleep, Gondek speculates, this part of the brain may analyze sounds to decide whether the person needs to be awakened to respond. This mechanism would allow a camper in the woods to sleep through non-threatening cricket chirps. But it might awaken the camper quickly to the growl of a bear.

Gondek and Krauss are planning follow-up experiments to learn more about how the brain processes specific environmental sounds during sleep. Their research may also shed light on connections between sleep disorders and mental illnesses such as depression and dementia.

Finding the place where the brain processes sounds during sleep has been a critical first step to cracking a tough physiological puzzle. "At this point," Gondek explained, "we can say that this is where it's happening. But it's still very unclear what's going on there, how this processing works."

When she's not engaged in challenging lab projects, Gondek maintains a busy schedule on campus. She serves as a volun-teer admissions representative, worked on the 1997 Johns Hopkins Spring Fair and played on the women's varsity tennis team.

After her moment in the spotlight last week in Minneapolis, Gondek returned to the Homewood campus for some mundane challenges in the classroom. "It's back to reality," she sighed, "... and finals."