Experiencing a frightening event is likely something you'll
never forget. But why does it stay with you when other kinds of occurrences
become increasingly difficult to recall with the passage of time?
A team of neuroscientists from the Tulane University School
of Science and Engineering and Tufts University School of Medicine have been
studying the formation of fear memories in the emotional hub of the brain --
the amygdala -- and think they have a mechanism.
In a nutshell, the researchers found that the stress
neurotransmitter norepinephrine, also known as noradrenaline, facilitates fear
processing in the brain by stimulating a certain population of inhibitory
neurons in the amygdala to generate a repetitive bursting pattern of electrical
discharges. This bursting pattern of electrical activity changes the frequency
of brain wave oscillation in the amygdala from a resting state to an aroused
state that promotes the formation of fear memories.
Published recently in Nature Communications, the research
was led by Tulane cell and molecular biology professor Jeffrey Tasker, the
Catherine and Hunter Pierson Chair in Neuroscience, and his PhD student Xin Fu.
Tasker used the example of an armed robbery. 'If you
are held up at gunpoint, your brain secretes a bunch of the stress
neurotransmitter norepinephrine, akin to an adrenaline rush,' he said.
'This changes the electrical discharge pattern in
specific circuits in your emotional brain, centered in the amygdala, which in
turn transitions the brain to a state of heightened arousal that facilitates
memory formation, fear memory, since it's scary. This is the same process, we
think, that goes awry in PTSD and makes it so you cannot forget traumatic
experiences.'
This research was led by Tasker's lab and was conducted in
collaboration with the Jonathan Fadok lab of Tulane and the Jamie Maguire lab
of Tufts. Fadok is an assistant professor of psychology who holds the
Burk-Kleinpeter Inc. Professorship in Science and Engineering at Tulane.
Maguire is an associate professor of neuroscience at the Tufts School of
Medicine.
Resource: Science Daily