Guest blogger Katie Pham is a neuroscience Ph.D. student interested in visual processing and memory research. She was born in Hanoi and raised in Northern California. Outside of lab, she enjoys spending time with her cats, watching Family Guy, and reading literary fiction.
Our daily decisions are shaped by our brain’s selection of the most beneficial actions in a particular situation. Such selection requires continuous integration of both our internal state and the external environment throughout the day. As these conditions change, priorities shift. For example, when seated in the office at 2 p.m. and choosing to skip lunch to meet a deadline, eating swiftly becomes a top priority due to the onset of exhaustion and hunger. Subsequently, after completing work and enjoying a hearty dinner, eating is no longer a priority and spending time with loved ones takes precedence.
This dynamic decision-making process is closely linked to the dopamine signaling system in our brains, which tags certain things as rewarding and deserving of attention, adjusting based on the physical state of our body and our surrounding environment.1 While numerous studies connect dopamine to signaling rewards, recent research from the Department of Neurobiology and Behavior at Cornell University investigated how this chemical system navigates and prioritizes different rewards as our focus shifts throughout the day.
Dopamine serves as a special messenger in our brains, guiding our actions and decisions by helping us learn from positive and negative experiences. It shapes our behavior by encouraging the pursuit of activities that bring joy or satisfaction. When encountering something enjoyable or anticipating a reward, such as a delicious meal or a positive social interaction, a brain region called the ventral tegmental area spikes up its release of dopamine to other areas of the brain to signal excitement and anticipation. This creates a sense of motivation and pleasure. Conversely, when we encounter a negative experience, the ventral tegmental area reduces its ongoing dopamine release. In this manner, the dopamine signal reinforces the connection between the experience and the reward, teaching our brain which actions are good and worth repeating.1
Neuroscientists from Cornell University used zebra finches, small songbirds known for their romantic inclinations, to explore how the dopamine system weighs the value of food and positive social interactions in different contexts. Zebra finches are ideal subjects for studying social bonding due to their unique courtship behavior. From a young age, male zebra finches learn how to sing certain songs from the adult male birds in their environment. Throughout their lifetime, they invest a lot of time and effort to practice the songs they have learned. Finally, during mating season, male zebra finches use their songs to attract female birds.2 Both their singing behavior and the response of the female birds can be easily observed and recorded in a laboratory environment.
The researchers placed water-deprived male zebra finches in four environmental contexts, all containing a spout that dispenses water when the bird touches it, and observed how the birds’ behavior and dopamine release changed across the different contexts. They measured water consumption levels when the birds were alone versus when they were alone and singing, and then introduced a female to compare drinking rates when the birds were standing in front of her versus singing to her. Simultaneously, dopamine levels were measured in two brain regions that directly receive signals from the ventral tegmental area: Area X, part of the bird’s song production system that sends signals to the muscles in the throat, and MST, where the water rewards signal has previously been observed.3
When the birds were alone and not singing, the researchers observed the highest level of water consumption, with intake gradually decreasing as they became preoccupied with singing or the presence of a female. Notably, when singing to a female, water consumption was at its lowest. Concurrently, both Area X and MST showed dopamine signals related to water reward, being highest when the bird was alone and not singing and lowest when singing to a female. Interestingly, dopamine signals related to courtship singing were absent in MST and routed specifically to Area X. The researchers found that, when the male birds are singing to a female, dopamine release in Area X could be evoked in response to the female calls synchronized with the male’s song. Such synchronization was likely a reward signal for the act of courtship singing.
The result of this study demonstrate how the birds’ perception of what is rewarding changes based on their internal and external environments. During courtship song practice or when distracted by the presence of a female, water consumption became less rewarding, reflected in a corresponding decrease in the dopamine signal for water reward. The researchers also identified anatomically distinct dopamine pathways in zebra finches, carrying different signals related to water rewards and social communication. Both pathways dynamically adjusted their activity levels based on the birds’ current objectives.
As we reflect on the dynamics of the dopamine signaling system during decision-making, it becomes clear that our perception of rewards is adaptable. Our brains continuously make inferences, shaping our understanding of what is rewarding based on internal factors like hunger and emotional well-being as well as the external factors in our environment. Whether enticed by a delicious meal, finding joy in meeting tight deadlines or deriving satisfaction from positive social interactions, the dynamic nature of our desires is comparable to the ever-shifting priorities observed in zebra finches’ behavior and underscores the idea that we may not always know what we want until it emerges as a viable option.
Whether examining the intricate courtship behaviors of zebra finches or the daily decisions of humans, the dopamine signaling system plays a critical role in adapting to shifting priorities and guiding our actions. Its course of action within our brains invites contemplation on the nature of our preferences — how they evolve and crystallize based on the contextual landscape of our lives. Thus, understanding these intricate processes enriches our comprehension of the motivation behind our daily choices and the neural mechanisms that drive them.
References:
- Arias-Carrión, O., Stamelou, M., Murillo-Rodríguez, E., Menéndez-González, M., & Pöppel, E. (2010). Dopaminergic reward system: a short integrative review. International archives of medicine, 3, 24. https://doi.org/10.1186/1755-7682-3-24
- Chen, Y., Clark, O., & Woolley, S. C. (2017). Courtship song preferences in female zebra finches are shaped by developmental auditory experience. Proceedings. Biological sciences, 284(1855), 20170054. https://doi.org/10.1098/rspb.2017.0054
- Roeser, A., Gadagkar, V., Das, A., Puzerey, P. A., Kardon, B., & Goldberg, J. H. (2023). Dopaminergic error signals retune to social feedback during courtship. Nature, 623(7986), 375–380. https://doi.org/10.1038/s41586-023-06580-w
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