The Neuroscience of Dopamine: The Brain's "Reward Chemical"

Since its discovery in the brain, dopamine has been regarded by scientists as one of the brain’s most vital neurotransmitters. Though frequently portrayed in social media as a “pleasure hormone” or “reward molecule” [1], dopamine spans a range of processes beyond making us “feel good” and has important implications in neuroscience and in our everyday lives.

Dopamine is a neurotransmitter synthesised from the amino acid phenylalanine [2] that is produced mainly in the midbrain of the brainstem. The midbrain is divided into two main regions: the ventral tegmental area (VTA) and the substantia nigra [1-4]. Dopamine neurons in these regions project to other brain regions, forming pathways (Figure 1) involved in a wide range of cognitive processes. For example, the mesolimbic pathway, which forms when dopamine neurons in the VTA project to the nucleus accumbens, plays a role in rewarding experiences, and the nigrostriatal pathway, which forms when dopamine neurons in the substantia nigra project to the dorsal striatum, plays a role in movement [1, 3-5].

Figure 1. Main dopamine pathways in the brain (Boggio et al. 2023)

Dopamine binds to five different subtypes of dopamine receptors (D1, D2, D3, D4, and D5), activating a G protein. This triggers an increase or decrease in the concentration of the second messenger cyclic adenosine monophosphate (cAMP), depending on the receptor type (increase for D1 and D5 receptors, and decrease for D2, D3, and D4 receptors). In turn, this stimulates various cellular responses, such as the activation or deactivation of specific proteins that mediate various cognitive functions [1–3].

The most well-known cognitive function influenced by dopamine signalling tends to be the feeling of pleasure and reward [1,3]. However, it would be an oversimplification to say that dopamine makes us “feel good” during rewarding experiences. Dopamine is involved in reward prediction error (RPE), which is defined as the difference between the reward that is expected and the reward that is received [1, 3-5]. In other words, dopamine increases when a reward is better than expected, increasing the likelihood that future actions will be taken to obtain the reward again, and the opposite happens when the reward does not meet one's expectations [1,5].

An important finding regarding the role of dopamine in pleasure and reward is that when a reward is completely as expected, dopamine does not increase in response to the reward but rather in response to the reward’s cue [1,5]. This idea has become important in explaining the science behind addictive behaviors, such as excessive social media usage. On social media, cues such as notifications, messages, and likes increase dopamine by activating the mesolimbic pathway and satisfying the human need for social approval. It is important to note that these cues are unpredictable, as users cannot predict when they will receive a like. Previous research has determined that unpredictable cues tend to sustain long-term dopamine signalling compared to predictable cues and reinforce repeated engagement with social media, such as frequent checking. Another notable fact is that the cues are quantifiable, with a greater number of cues, such as more likes on a post, generally resulting in a greater activation of the mesolimbic dopamine pathway [5].

Beyond its role in pleasure and reward, dopamine also plays a vital role in voluntary movement [1,3]. This was demonstrated in the 1950s when Swedish neuropharmacologist Arvid Carlsson, the scientist who first discovered dopamine in the brain, inhibited dopamine transmission in rabbits, paralyzing the animals [1]. However, movement was restored when the rabbits were injected with L-DOPA, a precursor molecule used in the synthesis of dopamine [1,2]. This experiment formed the basis of understanding the role of dopamine in movement and led to the hypothesis that the movement-related symptoms of Parkinson’s Disease (PD), such as tremors, may be due to the death of dopamine neurons in regions of the brain, such as the substantia nigra [1–3].

Additionally, dopamine plays a role in working memory, emotions, endocrine function, gastrointestinal function, immune responses, and higher-level cognitive processes [1-3]. Dopamine is also often thought of as a “neuromodulator” that is directly or indirectly involved in nearly every cognitive function that occurs in the central nervous system and various functions that occur in the peripheral nervous system [1–4].

In overview, dopamine is far more than a “pleasure or reward chemical” and has important implications in medicine and in our daily lives. Research into dopamine has been pivotal in developing medical interventions against various neuropsychiatric disorders, such as Parkinson’s Disease, schizophrenia, and substance use disorder, and in better understanding the day-to-day actions and habits that define us as humans.

References

1. Dopamine: Current Biology

2. Dopamine in Health and Disease: Much More Than a Neurotransmitter

3. Dopamine Pharmacodynamics: New Insights

4. Reappraising the role of dopamine in adolescent risk-taking behavior - ScienceDirect

5. Social Approval, Reward Learning, and the Neurobiological Basis of Social Media Use: A Narrative Review | Journal of Consultation Liaison Psychiatry

Image Credits

Fig. 1.3, [Main dopamine pathways in the brain]. - Social and Affective Neuroscience of Everyday Human Interaction - NCBI Bookshelf

© 2025 Kaylyn K. | All rights reserved

Originally published at themedtales.com