There is some work being done on emotional/love systems, and I
recently heard an interesting interview on NPR with the author of a
book called _Anatomy of Love_, Dr. Helen Fisher. She had just
recently completed an informal survey about infatuation behavior that
revealed nothing really new but confirmed some patterns that she
wrote about in her book. She talked about biological bases--I assume
that is in the book.
That, along with _The Emotional Brain_ (forget the author), are
forming a growing body of literature about the biological systems
that control emotion.