Pain and rewards are considered "opponent yet interacting processes"
involving partly similar brain regions. Identifying brain responses to
rewards and their association with pain symptoms may help in
understanding the neurological basis of pain-related behaviors and lend
new insights into the brain areas involved in the critical transition
from acute to chronic pain.
Patterns of brain responses to rewards are a significant predictor of
pain symptoms - a link that is already present by adolescence - and may
be influenced by gene variants affecting pain sensitivity, reports a
study in PAIN®
, the official publication of the International Association for the Study of Pain (IASP).
‘Patterns of brain responses to rewards are a significant predictor of pain symptoms - a link that is already present by adolescence - and may be influenced by gene variants affecting pain sensitivity.’
"Distributed" feedback patterns to rewards predict heightened pain
sensitivity, according to the new research led by Frauke Nees,
Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg
University, Mannheim, Germany. The researchers write: "Our results
might provide a first step early in life in identifying possible risk
factors for future pain complaints."
Reward Responses and Pain Are Linked; Gene Variants May Play a Role
A group of more than 600 European adolescents were studied at two
times. At ages 14-15, the teens participated in an experiment in which
they could earn rewards - in the form of M&M's candies - for
performing a computer task. Functional magnetic resonance imaging (fMRI)
scans were performed to examine how the brain processed these rewards.
Two years later, the teens were evaluated on a commonly used pain
Patterns of reward processing at age 14-15 were evaluated as
predictors of pain complaints at age 16-17. The study also examined the
effects of two variants of the mu-opioid receptor gene (OPRM1) that have
previously been linked to differences in pain processing. These genetic
variants may affect not only responses to opioid drugs (such as
morphine) but also the body's natural or "endogenous" opioids (such as
The results showed that reward-related feedback responses in a brain
area called the dorsal striatum at age 14-15 predicted the magnitude of
pain symptoms at age 16-17. Whereas responses in another brain area
called the ventral striatum have been linked to reward processes, the
dorsal striatum has been implicated in planning, motor (movement)
processing, and habit learning.
For one of the two OPRM1 variants studied, pain complaints were
predicted by reward feedback-related responses in a more widely
distributed brain area, including the ventral striatum. Teens with this
genetic variant had a higher magnitude of pain responses.
Within the limitations of the experimental study - limited to healthy
children without any clinical pain problems - the results suggest that
"aversive" outcomes such as pain may be related to "appetitive" reward
outcomes. "Distributed brain response patterns during reward processing
may be significant predictors for pain complaints, partly depending on
an opioidergic genetic predisposition," Dr. Nees and colleagues
In an accompanying commentary, Dr. David Borsook of Boston
Children's Hospital highlights some important questions raised by the
new results, including whether an individual's "opioidergic tone" is a
real indicator of pain susceptibility and risk of developing chronic
pain. While further studies will be needed, he writes, "The door has
been opened for an intriguing process that may have a significant
influence on improving our approach to evaluating and treating patients