Researchers at the University of Bonn Hospital show
that the bonding hormone inhibits the fear center in
the brain.
Frightening experiences do not quickly fade from
memory. A team of researchers under the guidance of
the University of Bonn Hospital has now been able to
demonstrate in a study that the bonding hormone
oxytocin inhibits the fear center in the brain and
allows fear stimuli to subside more easily. This
basic research could also usher in a new era in the
treatment of anxiety disorders. The study has
already appeared in advance online in the journal
"Biological Psychiatry". The print edition will be
available in a few weeks.
Amygdala
Significant fear becomes deeply entrenched in
memory. Following a car accident, for example, it is
difficult to manage street traffic once again - even
screeching tires can evoke significant anxiety.
Scientists refer to this as "conditioning". Certain
images or noises are very closely intertwined in the
brain with the experience of pain or fear. Only
gradually does one learn that not every screeching
tire means danger. This active overwriting in the
memory is known as "extinction". "In this process,
however, the original contents of the memory are not
erased but instead merely overlaid with positive
experiences," explains Prof. Dr. Dr. René Hurlemann
from the Department of Psychiatry and Psychotherapy
of the University of Bonn Hospital. If there are
dangerous situations once again, the fear, which was
believed to have been already overcome, frequently
flares up once more.
Extinction is often used in therapy for anxiety
disorders. For example, a person suffering from a
spider phobia will gradually and increasingly come
face to face with spiders. First the patient has to
view photos of spiders and then look at living
examples until finally he holds a tarantula in his
hand. When people with an anxiety disorder
experience as frequently as possible the fact that
they do not need to fear the trigger, their fear is
reduced. "However, this can take a very long time,
because this confrontation with the fearful
situation frequently has to be experienced. In
addition, there may be relapses because the original
trace of fear is still anchored in the memory,"
reports Prof. Hurlemann. This is why therapists seek
a possibility for "overwriting" the fearful memory
in a faster and longer-lasting way.
It has been known for a long time that the hormone
oxytocin does not just have a bonding effect in the
mother-child relationship and in the case of sex
partners but that it is also considered to be
anxiolytic. The scientists at the Department of
Psychiatry and Psychotherapy at the University of
Bonn, together with their colleagues from the German
Cancer Research Center in Heidelberg and the
University of Chengdu (China) have now been able to
prove its helpful effect in overwriting fearful
experiences. "Oxytocin actually reinforces
extinction: Under its influence, the expectation of
recurrent fear subsequently abates to a greater
extent than without this messenger," says study
director Prof. Hurlemann, summarizing the result.
The team of scientists induced fear conditioning in
a total of 62 healthy male subjects. In the brain
scanner, using video glasses, the test subjects
viewed photos, for example of human faces. For 70
percent of the images, they received a very brief,
unpleasant electrical shock to the hand via
electrodes. "In this way, certain images were
associated with an experience of anxiety in the test
subjects' memory," explains Prof. Hurlemann. The
scientists used two methods to prove that this
pairing of a particular photo and pain was actually
anchored in the test subjects' brains: The
expectation of an electrical shock was demonstrated
by increased cold sweat which was measured via skin
conductivity. In addition, the brain scans prove
that the fear regions in the brain were always
particularly active.
Half of the test subjects received oxytocin via a
nasal spray. The rest received a placebo. Then the
extinction phase began in which the test persons
were shown the same pictures several times as before
but they no longer received electrical shocks. In
the men under the influence of oxytocin, the
amygdala, as the fear center in the brain, was
overall far less active than in the control group,
whereas fear-inhibiting regions were more
stimulated. Over time, the messenger caused the fear
to initially be somewhat greater but then it abated
to a far greater extent than without oxytocin. The
scientists explain this through the special effect
of the messenger: "Oxytocin initially reinforces the
test subjects' conscious impressions and thus the
reaction to the electrical shock, yet after a few
minutes, the anxiolytic effect prevails," explains
Prof. Hurlemann.
The scientists hope that anxiety patients can be
helped more quickly with the aid of oxytocin and
that a relapse can be better prevented. In addition,
the researchers presume that the hormone likely
facilitates bonding between the therapist and the
patient and thus the success of the treatment.
"However, this must first be demonstrated by
clinical studies," says the scientist from the
University of Bonn Hospital.
See also
Shedding new light on the formation of emotional
fear memories
For more information
Oxytocin Facilitates the Extinction of Conditioned
Fear in Humans, "Biological Psychiatry",
DOI: 10.1016/j.biopsych.2014.10.015
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