Tuesday, May 7, 2019

Motivational Systems in the Adolescent Brain

By Amna Tahir, Neuroscience, 2021

Motivational systems in adolescents can help drive their behavior in different circumstances. Different parts of the brain are involved in motivations and the effect in adolescents is different from that of adults. I chose this topic because motivational systems play a large role in the life of an adolescent. 

Davidow, J.Y., Foerde, K., Galván, A., and Shohamy, D. An Upside to Reward Sensitivity: The Hippocampus Supports Enhanced Reinforcement Learning in Adolescence. Neuron, Volume 92. (2016). Pages 93-99. Retrieved from https://www.sciencedirect.com

Davidow, Foerde, Galván, and Shohamy used a task that combined reinforcement and probability to find a link between learning and memory in situations where rewards were involved. They were able to find that the hippocampus was influenced by the presence of a reward and so it would affect how an adolescent could learn from experience. Using an fMRI, the researchers found there was a strong link between reinforcement learning and episodic memory. Episodic memory is the ability to recall a specific part, or “episode”, of a person’s past.


In the experiment, there were two parts; the learning phase and the memory test. In the learning phase, participants had to press a button to predict where they thought a butterfly would land and would gain probabilistic reinforcement and a photo of an object. In the memory test, the participants would see a picture of an object and would then have to decide if they thought the photo was old or new. Then, they would rate how sure they were in their decision. They were able to find, using these tests that adolescents connected their episodic memory to their reinforcement learning to get better results for positive outcomes rather than negative outcomes.


Somerville, L.H, and Casey, BJ. Developmental neurobiology of cognitive control and motivational systems. Elsevier, Volume 20. (2010). Pages 236-241. Retrieved from https://www.sciencedirect.com


In this article, the Somerville and Casey begin by writing about the forms of cognitive control. One form is being able to go against the temptation to achieve a long-term goal. While this form of control was considered to increase linearly, it was found to be decreased in the presence of a reward. For example, in gambling tasks, adolescents were found to make riskier gambles in comparison to adults. This was because there was an increase in the sensitivity to rewards in adolescents. The sensitivity to rewards peaked between the ages of 14-16 and then would decline, which explained why the adults were less likely to make the same risky decisions.

With the increase in sensitivity to rewards, the adolescent brain was found to also be at an increased risk for cognitive control capacity to be lowered depending on how much attention or suppression the tasks would require. Another thing mentioned in this article was the relationship between incentives and cognitive control. When it was found to be better for adolescents to suppress their response to the incentive, their cognitive control would suffer.


Galván, A. (2017). Motivational Systems. The neuroscience of adolescence (pp. 151-178). Cambridge: Cambridge University Press. https://www.cambridge.org/


Galván begins by explaining a reward is any stimulus that an organism will find to be pleasurable. However, to find the stimulus rewarding, there has to be a change in how the organism will respond to the stimulus and how the information from the stimulus is processed in the brain. She then explains the importance of the neurotransmitter Dopamine in the reward system. In rats, she talks about how the release of dopamine increases in adolescence when stimulates by changes in the environment or pharmacologically. There is also a lot of neurocircuitries involved in reward processing, especially in areas where there are plenty of dopamine-releasing neurons. A part of this neurocircuitry network that is involved in the reward system is the ventral striatum. This part of the brain is what allows an organism to analyze and respond to the reward.

After explaining how the reward pathways work, Galván explains different studies done focusing on reward systems. One of which is the MRI studies. In these studies, the researchers were able to find that around age 10 in females and 14 in males, the cerebral’s volume increases and at age 8 in females and 10 in males, the amount of grey matter in the brain peaks. In fMRI studies, the researchers were able to see how the reward system affected the brain as it happened. When providing an incentive, the striatal regions of the participant’s brain were activated. Lastly, Galván addresses the good and bad purposes of risk-taking and the rewards it provides in adolescents. A good role rewards play in adolescents is how it helps in learning. In risk-taking behaviors, adolescents would perform better when the reward was higher. This helped in facilitating learning.

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