Two dimensions of value: Dopamine neurons represent reward but not aversiveness

An example of a single dimension is illustrated. Credit: Christopher D. Fiorillo, KAIST

To make decisions, we need to estimate the value of sensory stimuli and motor actions, their "goodness" and "badness." We can imagine that good and bad are two ends of a single continuum, or dimension, of value. This would be analogous to the single dimension of light intensity, which ranges from dark on one end to bright light on the other, with many shades of gray in between. Past models of behavior and learning have been based on a single continuum of value, and it has been proposed that a particular group of neurons (brain cells) that use dopamine as a neurotransmitter (chemical messenger) represent the single dimension of value, signaling both good and bad.

The experiments reported here show that are sensitive to the value of reward but not punishment (like the aversiveness of a bitter taste). This demonstrates that reward and aversiveness are represented as two discrete dimensions (or categories) in the brain. "Reward" refers to the category of good things (food, water, sex, money, etc.), and "punishment" to the category of bad things (stimuli associated with harm to the body and that cause pain or other unpleasant sensations or emotions).

Rather than having one neurotransmitter (dopamine) to represent a single dimension of value, the present results imply the existence of four neurotransmitters to represent two dimensions of value. Dopamine signals evidence for reward ("gains") and some other neurotransmitter presumably signals evidence against reward ("losses"). Likewise, there should be a neurotransmitter for evidence of danger and another for evidence of safety. It is interesting that there are three other neurotransmitters that are analogous to dopamine in many respects (serotonin, norepinephrine, and acetylcholine), and it is possible that they could represent the other three value signals.

More information: "Two Dimensions of Value: Dopamine Neurons Represent Reward But Not Aversiveness," by C.D. Fiorillo et al Science, 2013.

Related Stories

Brain implant aims to stifle drug highs

date Jul 29, 2013

What happens if addicts get no high from the drugs they take? Researchers at Case Western Reserve and Illinois State universities have received a $390,000 National Institute on Drug Abuse grant to help answer the question.

Dopamine regulates the motivation to act

date Apr 29, 2013

The widespread belief that dopamine regulates pleasure could go down in history with the latest research results on the role of this neurotransmitter. Researchers have proved that it regulates motivation, causing individuals ...

Recommended for you

Diet rich in methionine may promote memory loss

date 5 hours ago

Memory loss has recently been associated with excessive silencing of genes through a process called methylation. Researchers at the University of Louisville investigated the effects of a diet rich in methionine—an amino ...

Intelligent neuroprostheses mimic natural motor control

date 18 hours ago

Neuroscientists are taking inspiration from natural motor control to design new prosthetic devices that can better replace limb function. In new work, researchers have tested a range of brain-controlled devices ...

Researchers create 'Wikipedia' for neurons

date 22 hours ago

The decades worth of data that has been collected about the billions of neurons in the brain is astounding. To help scientists make sense of this "brain big data," researchers at Carnegie Mellon University ...

User comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.