Dopaminergic control of preference for reward maximization and reward unpredictability during free choice.
Final Report Abstract
My work can be divided in three distinct parts: experimental, theoretical, and computational. At the experimental level, I used dopamine agonists to stimulate the release of dopamine in the brain of pigeons and alter their foraging activity. In contrast to similar experiments with rodents, our results show that non-selective stimulation of dopamine neurons (with apomorphine) has no effect on the behavior of pigeons that have to freely choose between a variable and a constant delay, as well as between a 50% and a 100% probability of reward. Also, pramipexole – a dopamine D2/3 receptor agonist – increases the aversion for high-cost options in tasks where drug-free rodents show increased attraction. These results indicate that the link between dopamine and the willingness to deploy effort may be weaker in pigeons than in rodents. At the theoretical level, I developed and extended a motivational theory initially suggested explaining the higher response rates observed under partial rather than continuous reinforcement in Pavlovian autoshaping. The theory posits that the higher response rates under reward uncertainty do not reflect preference, but a survival requirement: organisms “hope” for unreliably rewarded CSs and invest more foraging effort when food cannot be fully expected. I suggested that this theory is not limited to autoshaping in Skinner boxes, but can explain foraging behaviors of wild animals living in environments in which the risk of starvation is high. Finally, at the computational level, the theory was implemented and concretely showed how foragers come to put on more fat reserves in winter than in summer, despite reduced food amounts in the environment. Also, it was shown that enhanced motivation to seek food under uncertainty favors the occurrence of Lévy walks, a property of random search movements that relocates the individual in the environment and optimizes the chance of finding food. The mechanistic perspective proposed here is therefore promising and may contribute to orient current research in new directions. It also calls for a dialogue between research areas not used to interact, such as behavioral psychology, behavioral ecology, and reward neuroscience. The “surprise” in the execution of this project was to find that the stimulation of dopamine neurons does not promote foraging activity in pigeons. Given the well-documented fact that dopamine plays a crucial role in motivation and reward-seeking in rodents, the same phenomenon was also expected in pigeons. The reasons for such a functional difference with mammals is currently unknown but might be related to evolutionary divergences in the way of collecting food between these species.
Publications
- (2016). Motivational control of sign-tracking behaviour: a theoretical framework. Neuroscience and Biobehavioral Reviews, 65, 1-20
Anselme, P.
(See online at https://doi.org/10.1016/j.neubiorev.2016.03.014) - (2017). How unpredictable access to food increases the body fat of small passerines: a mechanistic approach. Behavioural Processes, 144, 33-45
Anselme, P., Otto, T. & Güntürkün, O.
(See online at https://doi.org/10.1016/j.beproc.2017.08.013) - (2018). Long-term behavioral sensitization to apomorphine is independent of conditioning and increases conditioned pecking, but not preference, in pigeons. Behavioural Brain Research, 336, 122-134
Anselme, P., Edeş, N., Tabrik, S. & Güntürkün, O.
(See online at https://doi.org/10.1016/j.bbr.2017.08.037) - (2018). Pigeons consistently prefer easy over harder access to food: no reversal after direct dopaminergic stimulation. Behavioral Neuroscience, 132, 293-301
Anselme, P., Dreher, T. & Güntürkün, O.
(See online at https://doi.org/10.1037/bne0000249) - (2019). How foraging works: uncertainty magnifies food-seeking motivation. Behavioral and Brain Sciences, 42, e35, 1-15
Anselme, P. & Güntürkün, O.
(See online at https://doi.org/10.1017/S0140525X18000948)
