“I hate myself, and my brain,” Pam Tusiani wrote in her journal while under 24-hour watch on the fourth-floor psychiatric ward of Baltimore’s Johns Hopkins Hospital. “Nothing is worse than this disease.”

When Tusiani wrote those words in 1998, doctors had little understanding of the disorder that was troubling her, and all these years later they have little more.

Trying to understand how the illness works — in hopes of finding a cure — strikes at the heart of psychiatry, indeed medicine in general. How does one replicate at the basic research level what one sees in a patient? How do you find the chemical root of a disease, especially one as complex and multifaceted as borderline personality disorder, or BPD?

Just as a smile takes dozens of facial muscles to execute, a particular emotional response to a stimulus requires a web of brain activity. The brain isn’t a series of one-way streets. It’s a hive of superhighways, and we can barely make out the cars, much less figure out where they came from, where they’re headed, what they’re carrying and why they’re on the road. We barely understand a healthy brain, so how are we to understand one haunted by psychoses?