Written by: Jacinda Taggett
Oftentimes when an individual encounters a rewarding situation, such as getting take-out food after a long week of working, their brain releases a chemical called dopamine. Dopamine is commonly known as the “pleasure chemical” of the brain, as it leads to feelings of motivation and satisfaction.
However, there are other purposes for this chemical, such as movement and learning. Learning that is associative (e.g., making connections) or involving rewards are best correlated with dopamine (Sharpe et al., 2017; Vrieze et al., 2013). Although most research done on dopamine and learning are conducted in rodent studies, we can look at how these findings can relate to clinical populations, such as Parkinson’s Disease and Schizophrenia, which both face cognitive deficits as a symptom of their disorders.
Schizophrenia: Dopamine Imbalances and Learning Deficits
When dopamine is unbalanced in the brain, neuropsychological symptoms arise. In the case of schizophrenia patients, their irregular amounts of dopamine can lead to various symptoms, such as hallucinations (too much dopamine in some parts of the brain) and lack of enjoyment (too little dopamine in other parts). In the situation of too much dopamine, this leads to what neuropsychologists call positive symptoms, and negative symptoms are when there is too little dopamine.
If we consider the literature suggesting that dopamine is responsible for certain aspects of learning, we can question whether dopamine also plays a role in cognitive deficits that are included in the schizophrenic population. If there is an association between dopamine and learning in this clinical population, we can then think about potential treatments to preserve cognitive function.
Research studies have shown that reward learning is impaired in individuals with schizophrenia, which has been seen in both human patients (Abohamza et al., 2020) and rodent models (Higa et al., 2017). Specifically, in a study by Cheng et al. (2022), schizophrenic individuals were seen with lower accuracy in a learning task with reward context although other forms of cognition such as personal reward valuation remained constant.
Connecting Dopamine and Learning in Schizophrenia
To further connect the dopaminergic explanation for learning in schizophrenia, a neuroimaging study from Sheffield et al. (2018) assessed dopamine activation in the brain during associative learning tasks. They found that these patients not only had deficits in cognitive outcomes (i.e., reaction time and accuracy in the tasks), but also had decreased dopamine activation from the parts of the brain responsible for receiving dopamine, the striatum and, more specifically, the caudate. The striatum is a brain region known for its role in movement, reward processing, and learning, with the caudate being a subregion.
Atypical antipsychotics, which are a common treatment for schizophrenia, are medications that primarily affect dopamine (and another chemical called serotonin), leading to more natural dopamine in the brain. In the literature, this form of medication has been seen to be a more effective treatment for cognitive deficits in schizophrenia. For example, in a study by Insel et al. (2014), when the dose of atypical antipsychotics were increased during a learning task in which the participants were “winning”, schizophrenic individuals had better learning rates. These findings indicate that reward plays an important role for learning in these individuals, especially considering their treatment plans.
Future Directions
Understanding whether dopamine has an impact on cognition for schizophrenic individuals is essential. Given that the onset of this disorder begins during college years (i.e., 18 to 25 years of age), more research needs to be done to ensure that learning can be repaired for these individuals while also minimizing their psychotic symptoms.
Future studies should look into observing these relationships on a molecular level by working with rodent models to provide a neuroscientific basis for psychological research in human patients. This research also needs to be applicable to real-world and educational environments since associative and reward learning is the main research focus in dopaminergic studies. Additionally, more studies need to be done on schizophrenic patients currently experiencing symptoms of psychosis, such as hallucinations or delusions, so we can accurately provide treatment to potential college students during their most debilitating moments. Although the ethical and conventional approaches to this are limited, it would be more applicable to real-world scenarios.
Until these questions are answered, only then can we strive for treatments that will allow schizophrenic individuals to succeed academically and achieve their goals.
References
Abohamza, E., Weickert, T., Ali, M., & Moustafa, A. A. (2020). Reward and punishment learning in schizophrenia and bipolar disorder. Behavioural Brain Research, 381, 8. https://doi.org/10.1016/j.bbr.2019.112298
Cheng, X., Wang, L., Lv, Q., Wu, H., Huang, X., Yuan, J., Sun, X., Zhao, X., Yan, C., & Yi, Z. (2022). Reduced learning bias towards the reward context in medication-naive first-episode schizophrenia patients. BMC Psychiatry, 22, 10. https://doi.org/10.1186/s12888-021-03682-5
Higa, K. K., Young, J. W., Ji, B., Nichols, D. E., Geyer, M. A., & Zhou, X. (2017, April). Striatal dopamine D1 receptor suppression impairs reward-associative learning. Behavioural Brain Research, 323, 100–110. https://doi.org/10.1016/j.bbr.2017.01.041
Insel, C., Reinen, J., Weber, J., Wager, T. D., Jarskog, L. F., Shohamy, D., & Smith, E. E. (2014). Antipsychotic dose modulates behavioral and neural responses to feedback during reinforcement learning in schizophrenia. Cognitive, Affective & Behavioral Neuroscience, 14(1), 189-201. https://doi.org/10.3758/s13415-014-0261-3
Sharpe, M., Chang, C., Liu, M. et al. (2017). Dopamine transients are sufficient and necessary for acquisition of model-based associations. Nat Neurosci 20, 735–742. https://doi.org/10.1038/nn.4538
Sheffield, J. M., Ruge, H., Kandala, S., & Barch, D. M. (2018). Rapid instruction-based task learning (RITL) in schizophrenia. Journal of Abnormal Psychology, 127(5), 513-528. https://doi.org/10.1037/abn0000354
Vrieze, E., Ceccarini, J., Pizzagalli, D. A., Bormans, G., Vandenbulcke, M., Demyttenaere, K., Van Laere, K., & Claes, S. (2013). Measuring extrastriatal dopamine release during a reward learning task. Human brain mapping, 34(3), 575–586. https://doi.org/10.1002/hbm.21456
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