The brain’s reward system is a network of regions and pathways that drives how we feel pleasure, form habits, and motivate behavior.
It works by releasing chemicals (like dopamine) in response to rewarding activities, whether it’s eating, socializing, or achieving a goal. This evolved mechanism reinforces behaviors that are beneficial or enjoyable by making us feel good when we do them.
Key Takeaways
- The brain’s reward system motivates behavior by releasing dopamine in response to rewarding experiences.
- Dopamine drives learning, habit formation, and goal-directed actions by reinforcing behaviors that lead to pleasure.
- Two key pathways—mesolimbic and mesocortical—connect dopamine-producing areas to regions involved in motivation and decision-making.
- Anticipating rewards or receiving social approval (like social media likes) can activate the same brain circuits as physical rewards.
- Addiction occurs when this system is overstimulated, making the brain reliant on certain substances or behaviors for pleasure.
How the Brain Processes a Reward
Below is an overview of how the brain’s reward pathway operates when we encounter something rewarding:
Perception of a Rewarding Stimulus
A potential reward is first perceived, either as an external object (e.g. tasty food) or an internal thought.
The brain evaluates this stimulus – the hippocampus provides context from past experiences, and the amygdala adds emotional significance.
Activation of the Ventral Tegmental Area (VTA)
Recognizing the stimulus as rewarding triggers neurons in the ventral tegmental area (VTA) (a region in the midbrain) to activate and release dopamine, the primary “reward” neurotransmitter.
(For natural rewards, the VTA is activated by signals from other brain areas, whereas many drugs of abuse directly provoke dopamine release in the VTA.)
Dopamine Release to the Nucleus Accumbens (NAc)
The dopamine from the VTA travels along a neural highway called the mesolimbic pathway to the nucleus accumbens.
In the NAc, dopamine molecules bind to receptors on neurons, producing neural changes that correspond to feelings of pleasure and reward.
Reinforcement and Learning
The burst of dopamine in the NAc sends a signal to the prefrontal cortex (the part of the brain involved in decision-making and planning), which helps us link the reward to what we did to get it.
In essence, the brain notes “that was good – let’s remember how to do it again.” The stronger the dopamine response, the stronger this reinforcement signal, making us more likely to repeat the behavior in the future.
Feedback and Adjustment
The VTA, NAc, and prefrontal cortex then engage in feedback loops to fine-tune our behavior.
For example, if we expect a reward but it isn’t as great as hoped, these brain regions will dial down the motivation to pursue that stimulus next time.
This feedback helps us optimize our reward-seeking actions over time.
Reward Pathways in the Brain
Dopamine, the brain’s key reward neurotransmitter, is primarily produced in the ventral tegmental area (VTA), located in the midbrain.
From there, it travels through two major pathways involved in processing reward:
1. Mesolimbic Pathway: Driving Motivation and Pleasure
The mesolimbic pathway runs from the VTA to the nucleus accumbens (NAc), a region in the ventral striatum that plays a central role in motivation and reinforcement.
When we encounter something rewarding, dopamine neurons in the VTA fire and release dopamine into the NAc. This release creates the experience of pleasure and signals the brain that the behavior is worth repeating.
The nucleus accumbens is tightly connected to:
- The amygdala, which adds emotional intensity to rewards (e.g., joy after eating a favorite meal)
- The hippocampus, which encodes contextual memories of the reward (e.g., remembering where you got that food)
Together, these structures form a circuit that links pleasure, memory, and emotion, reinforcing goal-directed behaviors.
2. Mesocortical Pathway: Weighing Value and Guiding Decisions
The mesocortical pathway also begins in the VTA, but it sends dopamine to areas in the prefrontal cortex (PFC), especially the orbitofrontal cortex (OFC) and ventromedial PFC.
The prefrontal cortex is involved in planning, evaluating, and regulating behavior. Dopamine in this region helps us:
- Reflect on past rewards
- Weigh potential outcomes
- Make decisions based on long-term goals
While the mesolimbic pathway handles the feeling of reward, the mesocortical pathway helps us think critically about how, when, and whether to pursue it again.
Classic studies of desire and reward
In 1954, Olds and Milner completed experiments with rats to investigate which brain regions may be involved in rewards. They implanted electrodes at various points in the brains of the rats, which were then placed into a ‘ Skinner box.’
This contraption comprises a small chamber used to conduct conditioning research on animals, with a lever inside. When the rats would press the lever, they would receive a mild burst of electrical stimulation to their brains.
Their results indicated that there were various areas in the brain where the electrical stimulation is rewarding, so the rats would press the lever frequently to receive this rewarding sensation.
One of the rats in this experiment pressed the lever 7500 times in 12 hours to receive this electrical stimulation.
The reward area, which was most apparent when electrodes were placed there, was in the septal region, an area in the lower medial surface of the frontal lobe, with connections from the hippocampus, amygdala, and thalamus, among other areas.
Eventually, these rats would sometimes choose to receive the electrical stimulation rather than eat food.
In another experiment with more lenient conditions, the rats would eat enough food to thrive but would then spend the majority of the rest of their time excessively pressing the lever for stimulation.
Other scientists were able to replicate similar findings to these in their experiments on primates and humans (Heath, 1972; Sem-Jacobsen, 1976).
How Addiction Hijacks the Reward System
Addiction occurs when the brain’s reward system becomes overstimulated, reinforcing certain behaviors to the point that they become compulsive—even when harmful.
Normally, dopamine is released during pleasurable experiences, reinforcing behaviors like eating, socializing, or achieving goals.
However, addictive substances—such as stimulants, opioids, nicotine, and alcohol—trigger unnaturally high dopamine surges.
These substances either force more dopamine to be released or block its reabsorption, making the experience feel more intense and last longer than typical rewards.
Over time, the brain adapts. It becomes less responsive to normal levels of dopamine and starts relying on the addictive substance—or behavior—to feel good.
Everyday activities that once brought pleasure now feel dull by comparison. This shift can also lower levels of serotonin, a neurotransmitter linked to mood, leading to feelings of emptiness or depression.
Importantly, addiction isn’t limited to drugs. Behaviors like gambling, binge eating, or compulsive social media use can also overactivate the reward system.
As with substances, the brain learns to seek these behaviors for the dopamine hit, eventually reinforcing them through habit and craving.
In short, addiction is the result of the brain’s learning system being hijacked. Once the behavior is wired into the brain’s reward pathways, it can become difficult to stop—even when the consequences are negative.
Anticipation and Social Rewards: What Modern Research Reveals
Recent research shows that the brain’s reward system responds not only to receiving rewards but also to anticipating them.
In a study by Spreckelmeyer et al. (2009), participants underwent fMRI scans while they expected to receive money.
Even before receiving any reward, the dopamine pathways—including areas like the ventral tegmental area (VTA)—became active.
The greater the potential reward, the stronger the brain’s response. This suggests our brains begin “celebrating” rewards in advance, adjusting motivation based on what’s at stake.
Social rewards can trigger the same system. In today’s digital environment, one common form is receiving “likes” on social media.
Sherman et al. (2018) studied adolescents using a simulated photo-sharing app while inside an fMRI scanner.
When participants received many likes on their photos, their VTA and nucleus accumbens showed increased activity—similar to responses seen with monetary or food rewards.
Interestingly, even giving likes to others activated the reward system, though to a lesser degree.
These findings highlight that the brain’s reward circuits are deeply involved in anticipation and social validation—not just tangible rewards.
Whether expecting money or receiving digital approval, our brains process these experiences in similar ways, reinforcing behaviors that lead to positive feedback.
References
Ekhtiari, H., & Paulus, M. (2016). Neuroscience for Addiction Medicine: From Prevention to Rehabilitation-Methods and Interventions. Elsevier.
Heath, R. G. (1972). Pleasure and brain activity in man: Deep and surface electroencephalograms during orgasm. Journal of Nervous and Mental Disease, 154, 3–18.
Olds, J., & Milner, P. (1954). Positive reinforcement produced by electrical stimulation of septal area and other regions of rat brain. Journal of Comparative and Physiological Psychology, 47 (6), 419–427
Sem- Jacobsen, C. W. (1976). Electrical stimulation and self- stimulation with chronic implanted electrodes: Interpretation and pitfalls of results. In A. Wauquier & E. T. Rolls (Eds.), Brain- stimulation reward (pp. 505–520). Amsterdam: Elsevier- North Holland.
Sherman, L. E., Hernandez, L. M., Greenfield, P. M., & Dapretto, M. (2018). What the brain ‘Likes’: neural correlates of providing feedback on social media. Social cognitive and affective neuroscience, 13(7), 699-707.
Spreckelmeyer, K. N., Krach, S., Kohls, G., Rademacher, L., Irmak, A., Konrad, K., Kircher, T. & Gründer, G. (2009). Anticipation of monetary and social reward differently activates mesolimbic brain structures in men and women. Social cognitive and affective neuroscience, 4 (2), 158-165.
