By examining how our evolutionary history has shaped the neural pathways associated with pleasure and reward, we gain a deeper understanding of the motivations that drive human behaviour and the challenges that our evolutionary reward circuits create for us when navigating the influence of a multitude of pleasures within the modern world.
Reward circuitry systems as a survival mechanism
It is well established in modern biological theory that organisms are the result of evolutionary competition. Only genes that lead to the fittest phenotype1 will make it. The phenotype must survive and generate offspring, and be better at it than its competitors. Thus, the ultimate function of rewards is to increase evolutionary fitness by ensuring the survival of the organism and reproduction.
In short, behavioural reward functions have evolved to help us survive and propagate our genes, and it’s pleasure that drives the prime reward functions of learning, behaviour, and decision making.
Pleasure: the primary effect of rewards
We are attracted by most rewards and exert intense efforts to obtain them, just because they are enjoyable (Anselme P, Robinson MJ (2016) cited in Blum, K, et al., 2018).
Pleasure is a passive reaction that derives from the experience or prediction2 of reward. It promotes positive feelings and even better cognition, through the release of dopamine (Kirk, U, et al., (2015) cited in Blum, K, et al., 2018). Pleasurable activities can stimulate personal growth and may help to induce healthy behavioural changes, including stress management (Blum, K, et al., (2012) cited in Blum, K, et al., 2018).
But, as much as pleasure can serve cognition, productivity and health, simultaneously it promotes negative behaviours, i.e. motivational toxicity, and addiction.
The role of dopamine in reward circuits
There are several neurotransmitter systems that play an integral role in reward processing in the brain of Homo sapiens (humans). In this post, we focus on the neurotransmitter dopamine.
Dopamine, the brain’s pleasure messenger, plays a pivotal role in our neurological landscape. Most positive reinforcers like sex, food, gambling and aggressive thrills, as well as alcohol and other drugs cause the release of dopamine which is strongly associated with feelings of pleasure and reward (Blum, K, et al., 2018). This rush of dopamine encourages us to repeat the behaviour that leads to the pleasurable experience.
However, when the delicate balance of dopamine is disrupted, it can lead to a cascade of challenges.
Deficiencies in the brain’s reward cascade
The release of dopamine is facilitated by the interaction of many other brain chemicals in what is known as the Brain Reward Cascade. Deficiencies in the brain’s reward cascade, either hereditary or environmental (epigenetically produced), are responsible for impulsive, compulsive, and addictive behaviours both substance and non-substance and can result in Reward Deficiency Syndrome (RDS)3 and the manifestation of symptoms of depression like appetite changes, feelings of sadness, and psychomotor effects (Gold, M, et al., 2018).
Exposure as an adult or during childhood and in utero, to environmental factors such as stress, trauma, and social defeat epigenetically alter brain reward mechanisms and symbiotically impart vulnerability to addiction.
Imbalances in dopamine levels are implicated in conditions like ADHD and addiction. Elevated dopamine levels have been linked to heightened aggression and difficulties in controlling impulses (Source).
Individuals, genetically predisposed to crave (“want”) dopamine release due to environmental and genetic factors that can, especially, in combination, cause dopamine depletion4 5(Charles, A, et al. 1985) are at higher risk for addiction.
Achieving homeostasis6 in brain dopamine levels becomes paramount, not only for managing conditions like ADHD and addiction but also for fostering a healthier environment for impulse control. Thus, emphasising the importance of maintaining equilibrium for a harmonious interplay between our brain and behaviour.
Finally, enter Anselme & Robinson (2016), cited by Blum, K. (2018), shedding light on the conscious and subconscious tug-of-war in our pleasure-seeking behaviours. Most of our actions and goals are believed to be under conscious control, but what we find pleasurable is said to be driven by our subconscious. Our limited awareness of the underlying factors propelling us towards specific substances or activities that trigger reward circuits makes it challenging to consciously regulate motivation and addiction.
The ongoing discourse revolves around the interaction between genetic predispositions and environmental influences. The challenge resides in our ancient genes attempting to cope with the swiftly evolving modern world, particularly in the domains of impulse control, motivations, and susceptibility to addictive proclivities.
So, how does understanding this pleasure-reward system help in everyday life?
Motivation and Goal Setting: Knowing that dopamine is intricately linked to motivation helps individuals set and achieve goals. Recognising the reward-driven nature of motivation can inform strategies for maintaining focus and persistence in pursuing tasks.
Healthy Habit Formation: Understanding how dopamine reinforces behaviours can aid in forming and maintaining healthy habits. By associating positive rewards with health-related activities, such as exercise or healthy eating, individuals can make these behaviours more sustainable.
Addiction Awareness: Awareness of dopamine’s role in addiction can help individuals recognise the potential risks of certain behaviours and substances. This knowledge can contribute to making informed choices and avoiding activities that may lead to addictive patterns.
Modern Diet: Our pleasure-reward circuits play a significant role in influencing dietary choices. The brain’s response to pleasurable sensations from certain foods can impact our eating behaviours. This can lead to a preference for foods that provide immediate satisfaction, potentially contributing to unhealthy dietary habits and challenges in maintaining a balanced and nutritious diet. Understanding these neural mechanisms is crucial in addressing and managing issues related to diet and promoting healthier eating patterns.
Mood Regulation: Recognising the link between dopamine and mood can empower individuals to adopt lifestyle choices that support mental well-being. Activities that naturally boost dopamine levels, such as exercise or social interactions, can be incorporated into daily routines.
Stress Management: Dopamine is involved in the stress response. Understanding this connection can inform stress management strategies, encouraging individuals to engage in activities that promote dopamine release, such as relaxation techniques or hobbies.
Key points:
- The ultimate function of rewards is to increase evolutionary fitness by ensuring the survival of the organism (i.e. the human) and reproduction.
- Pleasure is the primary effect of rewards and promotes positive feelings and even better cognition.
- Research shows that positive reinforcers like sex, food, gambling, alcohol and other drugs cause the release of the neuro-transmitter dopamine.
- Dopamine is the “feel good” neuro-transmitter which is strongly associated with feelings of pleasure.
- This rush of dopamine encourages us to repeat the behaviour that leads to the pleasurable experience.
- Exposure as an adult or during childhood and in utero, to environmental factors such as stress, trauma, and social defeat epigenetically alter brain reward mechanisms.
- Deficiencies in brain reward mechanisms can cause Reward Deficiency Syndrome (RDS) and depression symptoms.
- Pleasure-seeking behaviours and goal-directedness are primarily under conscious control
- What we find pleasurable may be influenced by the subconscious, rendering it challenging to consciously regulate motivation and addiction.
- Reward circuit research suggests a real need for balancing brain dopamine to induce homeostasis.
- Understanding dopamine’s role in the pleasure-reward system can help in everyday life.
References
Anselme P, Robinson MJ (2016) “Wanting,” “liking,” and their relation to consciousness. J Exp Psychol Anim Learn Cogn 42: 123–140.
Blum K, Baron D, Lott L, Ponce JV, Siwicki D, Boyett B, Steinberg B, Modestino EJ, Fried L, Hauser M, Simpatico T, Downs BW, McLaughlin T, Hajela R, Badgaiyan RD. In Search of Reward Deficiency Syndrome (RDS)-free Controls: The “Holy Grail” in Genetic Addiction Risk Testing. Curr Psychopharmacol. 2020;9(1):7-21. PMID: 32432025; PMCID: PMC7236426.
Blum K, Dennen CA, Elman I, Bowirrat A, Thanos PK, Badgaiyan RD, Downs BW, Bagchi D, Baron D, Braverman ER, Gupta A, Green R, McLaughlin T, Barh D, Gold MS. Should Reward Deficiency Syndrome (RDS) Be Considered an Umbrella Disorder for Mental Illness and Associated Genetic and Epigenetic Induced Dysregulation of Brain Reward Circuitry? J Pers Med. 2022 Oct 14;12(10):1719. doi: 10.3390/jpm12101719. PMID: 36294858; PMCID: PMC9604605.
Blum K, Gondré-Lewis M, Steinberg B, Elman I, Baron D, Modestino EJ, Badgaiyan RD, Gold MS. Our evolved unique pleasure circuit makes humans different from apes: Reconsideration of data derived from animal studies. J Syst Integr Neurosci. 2018 Jun;4(1):10.15761/JSIN.1000191. doi: 10.15761/JSIN.1000191. Epub 2018 Feb 28. PMID: 30956812; PMCID: PMC6446569.
Charles A. Dackis, Mark S. Gold, New concepts in cocaine addiction: The dopamine depletion hypothesis, Neuroscience & Biobehavioral Reviews, Volume 9, Issue 3, 1985, Pages 469-477, ISSN 0149-7634, https://doi.org/10.1016/0149-7634(85)90022-3.
Gold, M.S., Blum, K., Febo, M., Baron, D., Modestino, E.J., Elman, I. and Badgaiyan, R.D., 2018. Molecular role of dopamine in anhedonia linked to reward deficiency syndrome (RDS) and anti-reward systems. Front Biosci (Schol Ed), 10(2), pp.309-325.
Kirk U, Brown KW, Downar J (2015) Adaptive neural reward processing during anticipation and receipt of monetary rewards in mindfulness meditators. Soc Cogn Affect Neurosci 10: 752–759.
Footnotes
- Phenotype refers to an individual’s observable traits, such as height, eye color and blood type. A person’s phenotype is determined by both their genomic makeup (genotype) and environmental factors. (Source) ↩︎
- Researchers found that a gene called tyrosine hydroxylase (TH) for the enzyme responsible for the production of dopamine was expressed in the neocortex (the part of the brain that is responsible for attention, thought, perception and episodic memory) of humans, but not chimpanzees. Nora Volkow, the director of NIDA, pointed out that one alluring possibility is that the neurotransmitter dopamine plays a substantial role in humans’ ability to pursue various rewards that are perhaps months or even years away in the future. This same idea has been suggested by Dr. Robert Sapolsky, a professor of biology and neurology at Stanford University. Dr. Sapolsky cited evidence that dopamine levels rise dramatically in humans when we anticipate potential rewards that are uncertain and even far off in our futures, such as retirement. (Source) ↩︎
- Reward Deficiency Syndrome (RDS) involves dopamine resistance, a form of sensory deprivation of the brain’s reward or pleasure mechanisms. The syndrome occurs because of an individual’s inability to derive reward from ordinary, everyday activities. (Source) ↩︎
- A deficiency or absence of DRD2 receptors then predisposes individuals to a high risk for multiple addictive, impulsive, and compulsive behaviours. ↩︎
- Notably, abnormal dopamine levels have been linked to disorders including Parkinson’s, schizophrenia and spectrum disorders such as autism or RDS (Blum, et al., 2014). ↩︎
- Any self-regulating process by which an organism tends to maintain stability while adjusting to conditions that are best for its survival. If homeostasis is successful, life continues; if it’s unsuccessful, it results in a disaster or death of the organism. ↩︎