"The role of the physician is to express confidence. The job of the scientist is to express doubt."
(The investigator tactfully predicted the presenter had a bright future in healthcare).
This distinction between medical types and research types is already apparent from the start of classes. At my school, the first-year lecturers are often researchers, and these biochemist or genetics PhDs pull double-duty by lecturing to the graduate school, as well.
As a mudphud student, I've seen the lecturers get perplexed by the different audiences. Grad students try to pick apart presentations -- challenging weak spots, and offering alternative explanations for conclusions. The professors usually find the exercise stimulating, and rise to the occasion.
On the other hand, the med students often either passively record and memorize, or try to extrapolate for patient care. Too many times, an hour-long lecture ends with the presenter awkwardly asking for questions. "None? Not one? Really? Anybody?"
Cheer up, professor. Their silence doesn't mean they weren't listening. Rather, take it to mean the med students trusted your authoritative tone. It's something they're trying to cultivate in themselves: you spoke with confidence.