The Function of the Effects of Risk Reward on Dopamine

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Biology 202, Spring 2005
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The Function of the Effects of Risk Reward on Dopamine

Imran Siddiqui

In my previous paper I briefly discussed how risk and reward are related to dopamine functions in the brain. In this paper I will delve deeper into this relationship and ultimately try to answer the question: what function does the risk/reward relationship to dopamine have within the every day function of both humans and animals? In doing so, more questions about risk/reward and dopamine will arise, and I well also attempt o discuss those in further detail.

In the previous paper I discussed a study that monitored dopamine levels in monkeys when they were given rewards to certain stimulus(1). The experiment found that when the monkeys were given a reward randomly, that dopamine levels increased. The study concluded that people worked similarly and showed similar increases in dopamine levels when given a random reward. Ultimately, this was one reason why humans enjoy gambling (1). I was very intrigued by the fact that risk reward causes dopamine release, and wondered why this was a necessary characteristic for humans to have. However, before I researched directly toward this question, I first wanted to do further research on the studies like the example above.

A similar study conducted at Concordia University also used monkeys to detect dopamine fluctuations during risk/reward tasks. The monkeys were put in front of a computer screen which displayed different color visuals (2). During the experiments different color visuals would come up, and a reward (drop of syrup) was associated to a particular visual. During the study the scientists preformed three different types of such experiments. In one experiment the monkey would receive the reward every time the monitor showed reward visual. In the second experiment the monkey would not receive any rewards whether or not the monitor showed the reward visual. In the final experiment the monkey was given reward randomly 50% of the time the monitor presented the reward stimulus (2).

The results showed that in the first experiment dopamine levels rose only the first few times the stimulus showed and a reward was given. After the first few times, the monkey became used to the reward. It expected the reward, and the reward was always given. Therefore, the stimulus would no longer have an effect on dopamine levels (2). The second experiment also showed a similar fluctuation in dopamine levels. At first, the monkey would expect to be given a reward after the monitor presented the reward stimulus. However, after the monkey was not given a reward, and continued to not be given a reward, the dopamine levels were no longer effected (2). The final experiment produced some very interesting results. Because the monkey would be rewarded randomly, the dopamine levels rose every time the monitor displayed the reward stimulus. If the monkey received a reward the monkey's dopamine levels would show a strong outburst. However, even before the monkey received the reward, dopamine levels rose in the monkey's brain. The underlying effect of this experiment was a constant increase in dopamine levels (2).

Now that this study has shown evidence to support the notion that risk/reward increases dopamine levels, I wanted to better understand what role does this function play in human's everyday lives? My initial hypothesis was that humans are creators, and in order to create humans must take risks. For example in order to develop an airplane the Wright brothers had to risk their lives by attempting to fly in machines that probably would not fly. However, the Wright brothers continued to attempt to fly, because the reward of creating a better flying machine made the happy (released dopamine). They did not know if a certain prototype would work, or what the results would be, therefore; the anticipation of the result also caused dopamine release. Without these dopamine releases, the Wright brothers would have had no incentive to try and retry to invent a flying machine.

At first this Hypothesis made sense to me, but later I realized that monkeys were used to replace humans in the experiment, and show the same kinds of dopamine release patterns. However, monkeys do not create as humans do. They do not invent. Therefore, there must be a more general use that this function of dopamine takes, and the incentive to create is only a byproduct of this more general functions within humans. I decided to research more into the actual reason for this dopamine function.

One of the major hypothesis that the literature on this subject proposed was that the dopamine response function to risk/reward acts a s learning mechanism (3). One study found that when dopamine increases, attention increases as well. This makes sense if we relate this back to the initial study. When the reward was given randomly the monkey's dopamine level would increase after the monitor displayed the reward stimulus, but before the reward was given (2). In this situation, it is likely that the dopamine increase functioned to increase the monkey's attention. But why would the monkey's attention need to increase?

Sources state that this increase in attention is used to increase the monkey's ability to learn from what is going on around it (3). Mainly, during the random reward phase of the experiment the monkey is trying to find use cognitive reasoning to find a pattern in the way the reward is being given. Once the monkey figures out the pattern, then the dopamine no longer responds to the stimulus or reward (4). This explains why in the first experiment where the monkey received a reward every time the monitor displayed a reward stimulus the monkey did not show dopamine increases. If dopamine does work this way in risk/reward situations, which there is ample evidence to support, then dopamine release in risk/reward situations is used as a learning tool (4).

This type of learning is called reward dependent learning. Dopamine release pushes animals or humans to not only do things that release dopamine, but also figure out patters for when certain things release dopamine and when they do not. This forces the animal or human to learn more about its environment, and what actions within the environment will produce positive results, and what actions won't. In animals specifically this works to improve choices that the animal makes in terms of finding food, shelter, and safety (4). One experiment conducted took one group of normal rats as the control, and one group of rats that had their dopamine release function blocked. Both rats were put in front of levers that they could push down if they walked over. Out of the group of levers one lever, when pressed, would cause the release of a pellet of food to the rat (4). The results of the experiment concluded that the rats with the dopamine blocked took far longer to learn which lever to press than the normal rats. This experiment supports the notion that dopamine release response to rewards is used to increase the learning capability of the animal. In humans, this would work very similarly (4).

However, how can this be related back to my original hypothesis that dopamine persuades humans to create? In fact, research has developed support for the hypothesis that dopamine is related to creativity. Furthermore, dopamine actually plays a role in how motivated a person is to achieve (5). Studies have proven that people who achieve more actually have more natural dopamine release than those who don't (6). But does this relate to the learning aspect of dopamine, or is this a different function? As I explained in my initial hypothesis earlier, I believe that achievement involves risk reward; therefore, achievement does work similarly to reward dependent learning. I feel that humans are intelligent enough to create and achieve; therefore, do so, and learn from it. However, I am still trying to make a more solid connection between reward dependent leaning and human aspirations towards achievement.

In conclusion, the one of the functions of dopamine reactions towards risk and reward is learning. Humans and animals alike use dopamine level increases to increase attention in order to learn what behavior will cause what effects. However, humans unlike animals have the ability to achieve create, and studies have shown a correlation between dopamine levels and achievement. It makes sense to me that achievement and creation is related to risk reward dopamine release. However, it is still unclear to me how achievement relates to reward dependent learning. I strongly feel that they are connected, because there is support to show that they are both results from dopamine level increases form risk/reward, but it is still unclear how. The research on achievement and dopamine is scarce (5), so hopefully there will be more conclusive results that will lead to more insight on the topic.

References

1)Hijacking the Brain Circuits With a Nickel Slot Machine

2)Gambling on Dophamine

3)Discrete Coding of Reward Probability and Uncertainty by Dophamine Neurons

4)Aneural Substrate of Prediction and Reward

5)Creativity and Addiction

6)The plunge of pleasure

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