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There are experiments [1] showing that our brain tries to maximize amount of dopamine. At the same time it is the brain who controls the dopamine level, because the reward system is located in the brain and if we'll stimulate specific brain areas, our body will produce dopamine.

My question is: why can't our brain learn to constantly stimulate this "reward system" area? Why it learns such complex things like doing math, playing chess, helping other people, etc., which in the far end increase dopamine level (by feeling "evrika" moment, winning a competition, seeing other people grateful) when it can just fool its reward system and manually send electrical signals into it? It is a much more easier and lucrative task.

P.S. I am not a biologist at all and will be very thankful if you formulate your answers easier than wikipedia articles which are a big struggle for me to comprehend.

P.P.S. I'd like to conduct some research in machine learning (neural networks, to be precise) and was thinking about how our brain prevents such devastating overfitting because underlying concepts can be very useful.

[1] Wikipedia page on the 'Reward system', History

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  • $\begingroup$ In general, all neurotransmitters have a negative feedback loop in the form of autoreceptors so that they don't get constantly pumped out... Also, neurotransmitters get recycled; this is called reuptake. What you mean to ask is probably a little different, something like why aren't dopaminergic pathways always stimulated or some such. $\endgroup$ – Fizz Nov 5 '17 at 15:17
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    $\begingroup$ And I'd give you a fuller answer, but it turns out it has been written by a science journalist already: theguardian.com/science/2013/feb/03/dopamine-the-unsexy-truth $\endgroup$ – Fizz Nov 5 '17 at 15:34
  • $\begingroup$ I like this question. In the context of machine learning, if you let your algorithm change the reward / loss function, it will just change it to maximize reward / minimize loss. If the brain is so powerful in learning, and the circuit is plastic enough to arbitrarily modify its activity to induce maximum dopamin (even in the presence of regulatory mechanisms), why doesn't it do so??? $\endgroup$ – Memming Nov 6 '17 at 15:02
  • $\begingroup$ @Fizz, thanks for the link. This article says, that reward system is something much more complex, than simply dopamine level in the blood, so it is useless for brain to just increase dopamine level. But this does not solve the problem and just reformulates it. (see next comment, I had to split it because of length limit) $\endgroup$ – Wunsch Punsch Nov 7 '17 at 15:32
  • $\begingroup$ Our brain has the power to stimulate its reward system and sometimes it does it indeed (during sex, for example). Then what's the problem for it to stimulate it constantly? It wants it so badly! In the experiment on wikipedia page I provided, a rat dies from exhaustion after hours of sending electrical signals into brain's reward system with a special device! What prevents our brain from constantly stimulating its reward system without any device? It has everything at its disposal for doing it! $\endgroup$ – Wunsch Punsch Nov 7 '17 at 15:32
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Short answer
Continuous activation of the reward system leads to habituation and hence a downregulation of the pleasure feelings. Further, a continuous euphoric state is a potentially harmful state, as behaviors essential to life are undermined.

Background
I'm having some difficulty what you mean with a brain fooling itself. A brain cannot fool itself. More importantly for the question, however, is that in case of the reward system it definitely doesn't want to 'fool itself'. Below I outline why from two different angles.

The evolutionairy perspective
In its very essence, the reward system is one of the most ancient parts of the brain and the use of dopamine neurons to mediate reward-driven behavior is also seen in worms and flies, which evolved around 1 billion years ago (Mount Sinai Medical School). Indeed, it's evolutionary role is to stimulate behaviors essential to the survival of an individual such as eating, but it is also essential for the survival of the continuity of an entire species by stimulating the drive for sexual reproduction (Melis & Argiolas, 1995). Reward should follow beneficial behaviors - continuous activation wouldn't aid anything other than a continuous euphoric state. An individual being euphoric wouldn't survive long as it wouldn't pursue anything any longer. That would quickly lead to a discontinuation of that trait as the individual would not be fit to reproduce (Darwin's survival of the fittest).

The physiological perspective
Continuous activation of the dopamine pathways quickly results in habituation (increasing resistance to the drug's effects) and, in the case of illicit drugs, to dependence (craving/compulsory drug seeking), together referred to as addiction (compulsive drug use despite harmful consequences). The downregulation of the receptors for dopamine (mainly D2) is a physiological reason reward sensations should be transient and uncommon, otherwise the reward system is being tuned down.

Reference
- Melis & Argiolas, Neurosci Biobehav Rev (1995); 19(1): 19-38

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    $\begingroup$ However, it's still interesting why brain does not do it periodically/randomly. While I agree with evolutionary perspective, there some things that are not useful in terms of reproduction/survival, such as playing games, feeling psychological support, etc, that is not covered by evolutionary perspective. $\endgroup$ – rus9384 Nov 6 '17 at 23:37
  • $\begingroup$ So, the only way to stimulate the reward system is by sending dopamine into special pathways; and our brain would be happy to do it constantly, but has 2 problems: 1) dopamine is a limited resource and 2) reward system quickly get's used to large amounts of dopamine. Did I get it right? $\endgroup$ – Wunsch Punsch Nov 7 '17 at 15:51

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