Dreams are mostly subconscious activity, your inhibitions are released perchance to realize suppressed fears, desires, wants, and needs. Those examples are maybe more important than 'common knowledge', for those aspects of life can deter an individual from their true potential. You might be thinking of Osmosis, which is a real thing, but not as most often thought of - Osmosis is the ability for the subconscious to absorb information in ones surroundings; such as advertisements, or staring at a page of writing, picture art, or listening to music, and in effect the information is not cognitively recognized, but retained none the less for possible recall at a later time.
It seems your professor was insinuating a belief in past-lives, I cant imagine any other way to learn a foreign language in your sleep; but that's a subject for another forum.