Document Type

Dissertation

Date of Degree

Spring 2016

Degree Name

PhD (Doctor of Philosophy)

Degree In

Neuroscience

First Advisor

Eliot Hazeltine

Abstract

Reward has been shown to improve multiple forms of learning. However, many of these studies do not distinguish whether reward directly benefits learning or if learning is boosted by modulation of top-down factors such as attention and motivation. The work outlined in this dissertation explores the modulatory effects of reward and punishment without directly manipulating top-down factors such as attention or motivation. We achieved this goal by studying the effects of reward and punishment on incidental learning – a branch of procedural learning where learning occurs without intention and through repetition. Our results reveal that reward is able to bolster incidental learning during the performance and learning of an associative task, even when awareness of how to achieve the reward is minimized (Experiments 1 and 2). However, a similar benefit was not observed in an analogous set of experiments examining the effect of punishment on incidental learning (Experiments 3 and 4). A direct comparison between the effect of reward and punishment on incidental learning revealed a significant advantage for rewarded combinations over punishment. However, this advantage was only observed when high cognitive (associative) demands were emphasized (Experiment 6), as opposed to high motor demands (Experiment 5). Finally, we explored the role of dopamine in the effect of reward on incidental learning. Because dopamine neuron dynamics have been implicated in both reward processing and in various forms of learning, we hypothesized that patients with Parkinson's disease (PD), who experience an accelerated rate of death of dopamine neurons, would experience impaired learning from rewards compared to healthy older adults. Experiment 7 revealed a significant impairment in reward-related incidental learning for patients with Parkinson's disease relative to comparisons. The amount of levodopa medication taken by PD patients predicted the effect of reward, demonstrating a potential link between dopamine levels and the effect of reward on incidental learning. Together, this dissertation demonstrates that 1) reward improves incidental learning, 2) reward may be an exceptional form of feedback, as opposed to punishments, and 3) dopamine levels may potentially drive the effect of reward on incidental learning

Public Abstract

Receiving a reward (such as money) is a desirable experience, but it is also associated with a change in brain chemistry. This change in brain chemistry is the release of the chemical “dopamine” from neurons in the human brain stem. These specific neurons release a large amount of the chemical dopamine over almost the entire brain. Dopamine has many effects on the brain, but one of the most important effects is improving how you learn skills (like shooting a basketball). This is why learning involving rewards is so beneficial. The purpose of my thesis is to determine whether rewards can improve learning, even when the learner has little idea of how to get the reward, and to see if dopamine is involved in this process

We designed a computer task where participants received rewards when they correctly categorized some sets of faces, but not on others. We found that our participants learned to categorize the rewarded faces better than the faces that were not rewarded. Critically, participants in our study were unable to tell us which trials yielded rewards, even though they benefitted from those rewards. This demonstrates that reward can benefit learning beyond simply improving motivation; just simply giving someone a reward is enough to improve learning.

We performed a similar experiment to see if punishments can also help improve learning. However, we did not see any benefit of punishments on learning. This means that something may be special about rewards, as opposed to punishments, that help you learn.

Finally, we wanted to find out if the chemical dopamine was linked to this effect. To do this, we studied two different populations: Patients with Parkinson’s disease and older adults without Parkinson’s disease. Patients with Parkinson’s disease have many fewer dopamine neurons than their healthy counterparts. Therefore, we predicted that the Parkinson’s patients would benefit less from rewards than the healthy older adults. Indeed, this is what we observed. This experiment demonstrates that dopamine neurons may be a critical factor that allow us to learn information better when we receive rewards.

Keywords

publicabstract, Dopamine, Feedback, Learning, Punishment, Reward, Task Demands

Pages

xv, 189

Bibliography

161-184

Copyright

Copyright 2016 Michael Vincent Freedberg

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