Desire and Dread are controlled by the same circuit in the brain
- From: Lance <LanceGary@xxxxxxxxx>
- Date: Thu, 20 Mar 2008 04:54:10 -0700 (PDT)
Changing stress levels can make brain flip from 'desire' to 'dread'
A single brain circuit mediates desire and dread according to a new
study by the
University of Michigan. Entering a noisy, new environment can
instantly flip an
emotion switch.
"We experience desire and fear as psychological opposites. But from
the brain's
point of view they seem to share a common kernel that can be flexibly
used for
either one," said Kent Berridge, a U-M psychology professor who
oversees U-M's
Affective Neuroscience & Biopsychology Lab. "This brain limbic circuit
can
retune its emotional functions from moment to moment, according to
situation.
"In some human disorders, this brain circuit might be more permanently
retuned
by pathology that unbalances the flexible circuit. For example, this
same
circuit might produce persistent desires in addiction, but fearful
emotions in
schizophrenia or phobias."
The study is featured in the April issue of the journal Nature
Neuroscience.
The nucleus accumbens is a brain structure mediating pleasure and
desire for
rewards that also participates in feelings of fear. U-M psychology
researchers
found the same group of neurons can flip back and forth, generating
either a
strong desire for food or an intense fear, depending on the mood of
the
situation when the neurons are activated.
U-M psychology researchers Sheila Reynolds and Berridge used a
painless
microinjection technique to put a tiny droplet of a drug (DNQX) into
about a
cubic millimeter of a rat's nucleus accumbens (in the front base of
the brain)
that was processing signals from the cortex.
The droplet chemically tapped a key on a limbic keyboard to generate
either a
positive desire to consume reward or a negative fear, depending on its
exact
location in nucleus accumbens.
If the tap was placed at the front of the brain structure, a positive
desire for
food and drink was generated, and the rats ate over eight times their
normal
amount of food. In the back of the structure, a negative fearful
emotion was
generated, and the rats displayed fearful behaviors that they would
otherwise
show naturally only to a threat such as a predator snake or a
scorpion.
Researchers found emotions produced by keys in the middle could be
retuned by
varying the mood of the situation. They administered the same droplets
of drug
in either the comfortable environment of the rat's own home or in a
more
stressful laboratory environment that included bright lights and loud
punk rock
music performed by one-time U-M student Iggy Pop.
Normally, the rats would rather be at home than in the bright lights
and music.
In the new environments, many keys of the nucleus accumbens keyboard
flipped the
emotions they generated. When given in the comfortable home situation,
the drug
droplets generated only positive desires in nearly the entire nucleus
accumbens.
But in the stressfully loud and bright situation, most of the
structure
generated intense fear in response to the same droplet.
The findings indicate that the same brain circuit can flip emotional
modes to
cause either desire or fear.
Source: University of Michigan
http://www.physorg.com/news125156642.html
.
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