2-Minute Neuroscience: Reward System

In my 2-Minute Neuroscience videos I explain neuroscience topics in about 2 minutes or less. In this video, I cover the reward system. I discuss dopamine's role in reward as well as the mesolimbic dopamine pathway, mesocortical dopamine pathway, ventral tegmental area, and nucleus accumbens.

For more neuroscience articles, videos, and a complete neuroscience glossary, check out my website at www.neuroscientificallychallenged.com !

TRANSCRIPT:

Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics in 2 minutes or less. In this installment I will discuss the reward system.

The reward system refers to a group of structures that are activated whenever we experience something rewarding like using an addictive drug. When exposed to a rewarding stimulus, the brain responds by increasing release of the neurotransmitter dopamine. Thus, structures that are considered part of the reward system are found along the major dopamine pathways in the brain. The pathway most often associated with reward is the mesolimbic dopamine pathway, which starts in an area of the brainstem called the ventral tegmental area, or VTA. The VTA is one of the principal dopamine-producing areas in the brain and the mesolimbic dopamine pathway connects it with the nucleus accumbens, a nucleus found in a part of the brain that is strongly associated with motivation and reward called the ventral striatum.

When we use an addictive drug or experience something rewarding, dopamine neurons in the VTA are activated. These neurons project to the nucleus accumbens via the mesolimbic dopamine pathway, and their activation causes dopamine levels in the nucleus accumbens to rise.

Another major dopamine pathway, the mesocortical pathway, also originates in the VTA but travels to the cerebral cortex, specifically to the frontal lobes. It is also activated during rewarding experiences and is considered part of the reward system.

Because dopamine is released whenever we use an addictive drug, researchers initially thought dopamine must be the neurotransmitter that causes pleasure. More recent research, however, suggests that dopamine activity doesn’t correlate exactly with pleasure. For example, dopamine neurons are activated before a reward is actually received and thus before the pleasure is experienced. For this (and other) reasons, it is now thought dopamine has roles other than causing pleasure, such as assigning importance to environmental stimuli associated with rewards and increasing reward-seeking.

Whatever the precise role of dopamine in reward is, the mesolimbic dopamine pathway is consistently activated during rewarding experiences, leading it to be considered the main structure of the reward system. Regardless, the actual network of brain structures involved in mediating reward is much larger and more complex than just this dopamine pathway, involving many other brain regions and neurotransmitters.

REFERENCES:

Berridge KC. The debate over dopamine's role in reward: the case for incentive salience. Psychopharmacology (Berl). 2007 Apr;191(3):391-431. Epub 2006 Oct 27.

Wise RA (1998). Drug-activation of brain reward pathways. Drug and alcohol dependence, 51(1-2): 13-22.