We are all well aware of how serious and, unfortunately, wide-spread drug addiction is, yet we don’t actually know what makes people so dependent of a drug after they have started using it. Even more intriguing is why former addicts, who have stopped using drugs for weeks or months, revert back to drug use, knowing full well that the substance they were addicted to in the past pretty much ruined their lives.
As I am sure you expect this article to shed light on the problem, I’m not going to keep you guessing. Two weeks ago, a team of researchers at the Icahn School of Medicine in US published a greatly revealing study in The Journal of Neuroscience. They appear to have found the answer to how cocaine affects decision-making in addicts as well as why abstinent users often choose to start taking cocaine again.
Dopamine is one of the commonest neurotransmitter in our brains. It is involved in many cognitive processes, including prediction and recognition of loss. Therefore, dopamine plays a very important role is some mental and also neurodegenerative diseases, such as schizophrenia (where dopamine levels are overly increased) and Parkinson’s disease (caused by decrease in dopamine secretion in the midbrain and degradation of dopamine receptors).
This recent study shows that cocaine acts on dopamine signalling, influencing the so-called Reward prediction error (RPE). It has been recorded, fallowing neuroimaging and pre-clinical studies, that dopamine signalling is increased in response to an unpredicted reward (which is scientifically referred to as positive RPE) and decreased as a result to a negative outcome or the omission of a predicted reward (negative RPE). The team of researchers demonstrated, therefore, that cocaine reduces the response to unpredicted loss (impaired negative RPE), while leaving the positive RPE almost intact.
In order to obtain these results, the team used 75 subjects, who were divided into two groups: 25 non-cocaine users and 50 cocaine addicts. Moreover, the second group was also divided as fallows: 25 cocaine users who had taken cocaine within 72 hours of the study and 25 cocaine users who had abstained from taking cocaine within 72 hours of the study. All subjects had to play a computer game that involved prediction and guessing.
As you may expect, the non-users responded normally to both unexpected loss and predicted reward, as well as to predicted loss and unpredicted positive outcome. On the contrary, the cocaine users responded far less to unexpected negative outcome. This means that their brains were reacting less strongly to the negative result of a prediction than the normal subjects’ brains.
Moreover, and this is the most fascinating part, the users who hadn’t taken cocaine within 72 hours, showed deficit in positive RPE, whereas the other addict group (who had consumed cocaine in the previous 72 hours), had unaffected positive RPE, but impaired negative RPE. Also dysregulation in serotonin system in drug addicts might lead to this kind of results (serotonin signalling has been registered in response to negative prediction, in normal brains).
So, to cut the story short and in a more simplified version, if you use cocaine, you are more likely to omit the bad things in your life. But if you take cocaine and then you give up, you get the opposite result: you become less able to enjoy positive aspects. This might account for the fact that people who stopped taking drugs tend to start using them again after rehab. Does this mean we have to become drug addicts? It seems like this is the solution. Well…NO! Definitely not! And I’m not saying this because I might get into trouble for promoting drug use, but there is a very important reason for that. We DO need to anticipate and recognize negative outcomes. This is how all creatures in this world survive. This is how more advances creatures (like humans) are capable of making good decisions and learn from mistakes.
Some might argue, though, that it is preferable to be happy all the time, despite how much you fail and that there is no such thing as actual failure, as it’s all about how our own brains perceive the environment. What do you think? Is this true or not? Either way, I strongly suggest you don’t start using drugs!
Image modified by Isuru Priyaranga
Finding Neuron 
Mulțumesc pentru răspunsul edificator ☺️ Înțelegând acum cat e de importantă dopamina, ce ar trebui sa facem ca s-o avem mereu in cantitatea optima (nici prea putina, dar nici in exces)?
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As dori sa aflu mai multe despre rolul dopaminei
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Aceasta e o intrebare care necesita un raspuns mai detaliat. Cum nu e destul spatiu aici, ma voi limita la cateva aspecte generale, iar pe viitor voi scrie un articol dedicat acestui subiect.
Prin urmare, dopamina este un neurotransmitator, in primul rand. Rolul lui este foarte important in creier, din mai multe motive.
1. Este precursorul metabolic al noradrenalinei (norepinefrinei)
2. Este implicat in controlul miscarilor voluntare – lipsa de dopamina este una din cauzele principale ale bolii Parkinson
3. Influenteaza “rasplata”, mai precis, este asociat cu comportamentul motivational, cu dorintele, cu “a vrea”. In trecut, dopamina era considerata substanta principala din spatele “placerii”. Acum se face distinctia intre “placere” si “dorinta” – creierul poate sa doreasca ceva ce nu ii place – explicatie pentru dependenta de droguri (voi detalia in articolul care urmeaza); de asemenea, s-a demonstrat ca deficitul de dopamina nu afecteaza senzatia de placere, ci nevoia de a cauta obiectul care genereaza placerea.
Motivatia este foarte importanta pentru supravietuire (animalul trebuie sa stie cand sa vrea mancare, de exemplu). De asemenea, dopamina joaca rol in anticipare si recunoasterea rezultatelor negative. Acest lucru poate fi deranjant (iti poate afecta starea de fericire), insa este, din nou, un aspect necesar pentru supravietuire. Deci, dopamina influenteaza luarea deciziilor corecte, privita din aceasta perspectiva.
Pe de alta parte, excesul de dopamina este asociat cu schizofrenia. Aici lucrurile devin putin mai complicate, deoarece se stie ca schizofrenia este “boala gandirii deficitare”. Cu toate acestea, putem simplifica putin lucrurile: excesul de dopamina declanseaza o anticipare si analiza distorsionata atat a aspectelor negative, cat si a celor pozitive. Astfel, pacientul este incapabil sa judece corect situatiile in care se afla.
Sper ca am reusit sa clarific, cat de cat, subiectul dopaminei.
Multumesc pentru interes! 🙂
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“I would like to find out more about the role of dopamine.”
This is a question that requires a more detailed answer. Unfortunatelly, it is not enough space here, therefore I’ll only focus on the general aspects regarding this subject, and in the future, I will write an article about this topic.
Having said that, let’s talk about dopamine!
First of all, dopamine is a neurotransmitter, a very important one even!
These are the main reasons why dopamine is so crucial in our central nervous system:
1. It is the metabolic precursor of noradrenaline (norepinephrine)
2. It is involved in the control of voluntary movements – the degradation of dopamine storages is thought to be one of the main causes of Parkinson’s disease.
3. It is involved in the “reward” system, thus influencing the adaptive behaviour. To be noted that dopamine doesn’t necessarily trigger pleasure. It generates the “wanting” though; it is associated with motivation. Even though in the past the two consepts were considered almost identical, scientists now differentiate between “desire” and “pleasure”. It has been demonstrated that the brain often wants things it doesn’t “like” (to put it simply). This could account for the drug addiction – I will discuss this in more detail in the upcoming article.
“Wanting” is extremely important for survival (the animal must want to eat, for example). Also, dopamine is involved in prediction and recognition of the negative outcomes, as well as the positive ones. Therefore, it plays an important role in decision-making.
On the other hand, the excess of dopamine has been shown to generate schizophrenia or at least, psychotic behaviours. This is a bit complicated, as schizophrenia is known as “the disease of thought disorder” (So how does an excess in something good for decission-making trigger something that is precisely characterised by impaired decision-making?) Well, think logically. Too much dopamine means distorted prediction and analysis of the negative and positive aspects, due to increased positive RPE and impaired negative RPE. Hence, the patient is uncapable of judging a situation properly.
I hope this topic is a little more clear now.
Thank you for your interest! 🙂
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