On Memory

Monday Musings” for Monday June 19, 2017
Volume VII. No. 25/337

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Post-traumatic Stress Disorder (PTSD)

by Assad Meymandi, MD, PhD, DSc (Hon), DLFAPA*

(Editor’s Note: Last week we interrupted the “MM” science series on Memory and Post Traumatic stress Disorder to observe Father’s day.  We resume the series toady, Part II concentrating on the topic of PTSD.

Science Series. Part  II:  Memory and PTSD

In her memoirs, Jacqueline Kennedy Onassis wrote of her flashbacks of the November 22, 1963 assassination of her late husband. She was suffering from PTSD. The official description of PTSD, or Post-traumatic Stress Disorder, published by Veterans Affair is “a psychiatric disorder that can occur following the experience or witnessing of a life-threatening events such as military combat, natural disasters, terrorist incidents, serious accidents, or physical or sexual assault in adult or childhood.”  Most survivors of trauma return to normal given a little time. However, some people will have stress reactions that do not go away on their own, or may even get worse over time. These individuals may develop PTSD. People who suffer from PTSD often relive the experience through nightmares and flashbacks, have difficulty sleeping, and feel detached or estranged, and these symptoms can be severe enough and last long enough to significantly impair the person’s daily life.

People with PTSD experience three different kinds of symptoms. The first set of symptoms involves reliving the trauma in some way such as becoming upset when confronted with a traumatic reminder or thinking about the trauma when you are trying to do something else. The second set of symptoms involves either staying away from places or people that remind you of the trauma, isolating from other people, or feeling numb. The third set of symptoms includes things such as feeling on guard, irritable, or startling “easily.”

It is estimated that 8 percent of Americans will experience PTSD at some point in their lives, with women twice as likely as men to develop PTSD. About 3.6 percent of U.S. adults aged 18 to 54 (5.2 million people) have PTSD during the course of a given year. This represents a small portion of those who have experienced at least one traumatic event. The traumatic events most often associated with PTSD for men are rape, combat exposure, childhood neglect, and childhood physical abuse. The most traumatic events for women are rape, sexual molestation, physical attack, being threatened with a weapon, and childhood physical abuse.

What does science have to offer?

In my daily reading diet I value several publications which include ScienceNatureNew England Journal of Medicine (NEJM) and Lancet.  Lately, I have been impressed by another journal PLOS ONE, a peer-reviewed open access scientific journal published by the Public Library of Science (PLOS). It is a publication that translates experimental laboratory data into clinical practice. It is one thing to accomplish or make discoveries in the laboratory with animals. But it may take years and years before the results are applied in clinical practice to humans. In that sense PLOS is unique. It is a truly translational journal. Its purpose is to speed up the process of applying laboratory discoveries into bedside patient care and clinical practice.

Published studies by Marc J. Kaufman, PhD, Director of the McLean Hospital Translational Imaging Laboratory and colleague Edward G. Meloni, PhD, are of seminal value and promise to have lasting benefit. In these studies, the scientists discovered that rat exposure to Xenon, a noble (inert) gas blocks traumatic memories. It becomes very useful to block bad memories in individuals suffering from PTSD. The chemistry is fancy but simple. Memories are stored and transmitted in specific parts of the brain called amygdala, hippocampus and frontal cortex. They are transported by many neurotransmitters in the brain from the memory centers to other parts of the brain. The most prevalent neurotransmitter charged with transporting memory is N-Methyl-D-Aspartate (NMDA). Just a word about what is a neurotransmitter– a neurotransmitter is like a bus or a car that carries instead of passengers, messages from one nerve cell (neuron) to other parts of the brain. The key to interfering with transmission of memory is to interrupt the neuronic flow mediated by NMDA. In essence, take a chemical scalpel and cut off or tie off the flow of NMDA. Well, the Boston scientists have hit the pay dirt. They discovered Xenon is the chemical that accomplishes the task and chemically interrupt or cut off NMDA transmission in rats. Here is an abstract of the publication.

Xenon (Xe) is a noble (inert) gas. These gases belong in group O of the periodic chart.  The group includes radon, helium, neon, argon, and krypton. Xenon gas has been developed for use in people as an inhalational anesthetic and in diagnostic imaging procedures. Xenon inhibits receptors involved in learning and memory and affect those parts of the brain, namely amygdala and hippocampus, responsible for memory formation and information storage. When Xenon is administered after memory of a trauma is formed (they call it fear memory), the memory disappears after the Xenon is administered. Male rats were used to develop this elegant animal model of PTSD they call fear-conditioning. The rats were trained to be afraid of environmental clues that were paired with brief foot shock. The researcher found that a single exposure to the Xenon gas blocked memory formation in the brain, dramatically and persistently reducing fear responses up to two weeks. The researchers are planning to apply the work to humans. The research holds much promise for those millions suffering from PTSD.

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*The writer is Adjunct Professor of Psychiatry, University of North Carolina School of Medicine at Chapel Hill, Distinguished Life fellow American Psychiatric Association, and Founding Editor and Editor-in-Chief, Wake County Physician Magazine (1995-2012). He is a dramaturge. Received Raleigh Medal of Art in 2001, inducted to Raleigh Hall of Fame 2013, elected Lifetime Trustee, North Carolina Symphony in 2015, and 2016 recipient of NC Award, Fine Arts.

 

 

 

 

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