From the BBC's "Tomorrow's World"
WEDNESDAY 15th December 1999

For the first time, a patient with multiple personality disorder has been monitored using an MRI scanner while switching characters. The scans showed marked changes taking place in her brain. Intriguingly the hippocampus, an area associated with long-term memory, switches off during the change to an alter ego and is reactivated on the switch back.

Multiple personality disorder (MPD) is a controversial area of mental health. It has been met with scepticism from some psychiatrists who feel the condition isn't genuine. Others say that while it's very rare, MPD is certainly real and usually stems from childhood trauma and abuse. They say the extra personalities are brought into being by the patient to protect themselves from the reality of their situation.

Carrying out tests like this has been difficult for two reasons. First, functional MRI's which can measure brain activity are only a recent innovation, and second finding a patient who can switch personality on demand while in a scanner is very unusual. The psychiatrists involved in the experiment say more work is needed to draw any general conclusions. Nevertheless, it provides some evidence that there may be a physiological basis to the condition.