Researchers from King’s College London have
identified a coordinated network of brain activity
which may explain how the brain anticipates and
processes rewards.
Brain activity during reward anticipation
The study, published in Proceedings of National
Academy of Sciences (PNAS), also highlights a novel
gene, known as ‘VPS4A’, that appears to regulate
levels of dopamine in key areas of the brain.
This genetic mechanism may explain how dopamine
levels increase when people anticipate a reward and
why problems with reward processing are found in
people with various mental disorders, including
attention deficit hyperactivity disorder (ADHD) and
addictions such as alcohol abuse.
It is possible that these impairments may involve
different components of the reward process,
including brain activity during the anticipation of
future rewards. Previous research has been limited
to very selected brain structures, whereas this
study is the largest and most comprehensive analysis
to date of brain activity during reward
anticipation.
Using data collected by IMAGEN, a large European
research project led by King’s College London, the
researchers examined brain regions engaged by reward
anticipation in 1,544 adolescents.
Reward anticipation was assessed through brain scans
of adolescents during a task where cues indicate
that either no reward, a small reward or a large
reward might be won during the trial. Participants
were then asked to respond to a target in order to
gain the reward.
By measuring blood oxygen-levels in the brain, the
researchers compared brain activity during the
anticipation of rewards with that of activity when
no rewards were anticipated.
They discovered a network of brain activity related
to reward processing in the cerebral cortex, which
is responsible for intelligence, language, memory
and consciousness, as well as regions below the
cerebral cortex (‘subcortical’ brain areas).
They also looked at associations between brain
activity and behavioural outcomes related to ADHD
and addiction, including measures of hyperactivity
and lifetime alcohol consumption. The researchers
found that reduced activity in the striatum - a
region of the brain known to be dysfunctional in
people with ADHD - was associated with higher levels
of hyperactivity. However, this association was only
observed in boys.
Finally, the study team selected adolescents with
very high hyperactivity scores and compared them to
individuals with no indication of hyperactivity.
They found that the correlation between
hyperactivity and activity in a subcortical region
of the brain was twice as strong in extreme cases of
hyperactivity, compared to those with no symptoms of
hyperactivity.
Professor Gunter Schumann, senior author of the
paper from the MRC Social, Genetic and Developmental
Psychiatry (SGDP) Centre at the Institute of
Psychiatry, Psychology & Neuroscience (IoPPN),
King’s College London, and Coordinator of the IMAGEN
project, said: ‘We already know that reward-related
disorders, such as ADHD and alcohol abuse, often
occur simultaneously. Our findings go some way
towards explaining how this relationship is driven
by common neural mechanisms, despite the fact that
both are currently diagnosed and treated
differently.
‘We have also discovered a gene that appears to
regulate dopamine activity observed in dysfunctional
reward processing, which may account for the
enduring nature of related mental health disorders.
‘These insights may be helpful in identifying what
is causing ADHD and alcohol abuse at a neural level,
and could be important for highlighting novel
treatment targets for techniques such as brain
stimulation.’
For more information
Proceedings of the National Academy of Sciences
The neural basis of reward anticipation and its
genetic determinants
Jia, T et al (2016)
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