Tai Sing Lee '86 works in a Harvard robotics lab constructing a mathematical model to explain how the brain detects surfaces and boundaries of objects.

Tom N. Kerrihard, a 4th-year Harvard-MIT graduate student, conducts research in the Beth Israel Hospital's psychiatry department in an attempt to distinguish between the pathological and non-pathological courses which lead to suicide.

Heidi L. Roth '87 is currently studying implicit and explicit memory, two classifications of memory which indicate whether a subject is conscious of remembering. She will graduate from the Medical School this June and pursue a residency in neurology.

Lee, Kerrihard and Roth are just three of the 30 Harvard Medical School students who each year choose to pursue an alternative course of study which emphasizes research over clinical aspects of medicine.

The Harvard-MIT Division of Health Sciences and Technology (HST) is a joint program between Harvard and MIT which encourages graduate students to engage in research which will enable them to pursue a Ph.D. or an M.D., or to obtain experience in non-degree-related research projects.

And Roth says HST has allowed her to discover her true inclinations.

"When I came I didn't want to commit," Roth says. "I knew I was interested in research but didn't know exactly [what kind]."

HST presents an annual scientific symposium, established in 1987, to provide students with an opportunity to discuss their work with the entire HST community.

This year's forum, which took place last month, included technical, biochemical, and behavioral projects indicative of the students' specific interests. Ten students gave 20-minute explanations of their research, and more than 25 displayed posters explaining their objectives, processes, and findings.

Roth's research has shown that brain-damaged patients often retain their implicit memory; she uses word tests to study patients' implicit memory.

For example, subjects are read a list of words before they are presented with the first several letters of a word, such as "cra." When asked to complete the word, the implicit memory begins to work; a subject is more likely to create a word he or she has recently heard (such as cradle) than to choose a different, unrelated word (such as crave).

Much of the research in which HST students are engaged is technical, involving mathematical and computer explanations for biological phenomena.

Lee's model, tested by computer simulation, is a means by which to simplify the complex neurobiological functions of the visual cortex and to make qualitative predictions about how cells respond to stimuli.

Lee described the relationship between his model and the actual brain: "We are trying to use biological findings of neuron responses to create a mathematical model." He said the model simulates the activity of brain cells.

Lee, who is currently finishing his Ph.D. thesis, said the differences between the HST program, and a Harvard Medical School's New Pathway curriculum, whose structure emphasizes case studies, provides "a more comprehensive and organized way" of studying medicine.