Fear Conditioning and Extinction in Twins Discordant for Combat Exposure and PTSD.
Abstract: Posttraumatic stress disorder (PTSD) is an anxiety disorder that
develops in a minority of people after exposure to a traumatic event. For these people,
previously non-emotional stimuli become associated with the traumatic event, causing a
significant amount of psychological distress. For instance, a veteran who served on a swift
boat may find that fishing boats evoke powerful emotio... read morenal reactions, due to an association
with his combat experience. Because PTSD involves emotional associations with an aversive
stimulus (like combat exposure), some researchers have chosen to frame PTSD in the context
of fear conditioning and extinction. "Conditioning" refers to the process of associating an
aversive stimulus with a neutral stimulus, which causes the neutral stimulus to acquire
aversive properties. This closely parallels the etiology of PTSD, where neutral stimuli
(like boats) can become associated with a traumatic event (like exposure to combat), and
may have the potential to illuminate how PTSD develops. "Extinction" refers to the process
of disassociating a previously neutral stimulus from the aversive properties that it has
acquired. This closely parallels the therapeutic technique of exposure therapy, which has
been successfully used to reduce or alleviate PTSD symptoms. The present paper will first
cover a brief history of fear conditioning research and explain the theory behind fear
conditioning as it pertains to PTSD. Afterward, this paper will compare fear conditioning
and extinction measures in PTSD and control groups, exploring each stage of the paradigm
separately: acquisition of the fear memory, extinction of the fear memory, and recall of
the extinction memory. Finally, this paper will describe an experiment aimed at
dissociating familial vulnerability factors from acquired PTSD characteristics, related to
fear conditioning and extinction. We report that a reduced differential fear response is a
familial vulnerability factor for PTSD, while reduced extinction recall is an acquired PTSD
Thesis (Ph.D.)--Tufts University, 2012.
Submitted to the Dept. of Psychology.
Advisor: Lisa Shin.
Committee: Heather Urry, Mohammed Milad, and Joseph DeBold.
Keywords: Psychology, and Psychobiology.read less