Q. I heard about a British stockbroker who lost his memory while on a train going to Coney Island. Is this the same condition portrayed in movies?

A. I am uncertain about the specific diagnosis of the British stockbroker. Amnesia is the label applied to a variety of conditions where an individual experiences partial or complete loss of memory. Some types have a psychiatric basis. For example:

• Dissociative Fugue, a form of amnesia, was portrayed in a book written by Robert Ludlum entitled “The Bourne Identity.” The story was made into a movie by the same name showing the protagonist, Jason Bourne, who had all memory of his prior life erased. It tends to have a very abrupt onset and usually occurs after a very traumatic event. Affecting less than 0.2% of people, Dissociative Fugue is often a temporary condition.
   
• Hollywood has also portrayed amnesias such as Multiple Personality Disorder (MPD) or Dissociative Identity Disorder (DID). This type of amnesia may affect about 1% of the population. The person’s sense of consciousness can split into two or more independent systems rather than remaining a single and integrated mental system. They can exhibit entirely different personalities at different times. Each “alter” may have its own name, its own view of the world, its own personal history, and a different sex. In a study of 100 cases, reported by Rita Carter in the book “Exploring Consciousness,” the average number of alters was 13.

MPD/DID was portrayed in the movies Sybil and The Three Faces of Eve. It may result after the person experiences severe or prolonged stress/trauma. People with MPD/DID can exhibit entirely different personalities at different times and/or have inexplicable blanks in their memory.

Doctors Steven Quartz and Terrence Sejnowski (authors of the book Liars, Lovers, and Heroes) indicated that 99% of people with DID have documented histories of severe and prolonged trauma during childhood. Temperament styles may contribute to differences in the way children react to traumas (e.g., one may be resilient, another vulnerable).

Other types of amnesia have a neurological basis, including:

• Anterograde Amnesia is a rare form of memory loss. The person can recall information prior to an injury event but can no longer transfer information into long-term memory. Scientists have concluded that this type of amnesia likely results from damage to the temporal lobes and the hippocampi (tiny brain organs that play a role in transferring memories from short term to long-term storage).
   
• Alzheimer’s Disease is another form of neurological amnesia. This disease is progressive in nature, but the individual typically is able to recall their own identity (at least until serious stages of the condition).