Percorrer por autor "Dayan, Peter"
A mostrar 1 - 2 de 2
Resultados por página
Opções de ordenação
- An effect of serotonergic stimulation on learning rates for rewards apparent after long intertrial intervalsPublication . Iigaya, Kiyohito; Fonseca, Madalena S.; Murakami, Masayoshi; Mainen, Zachary F.; Dayan, PeterSerotonin has widespread, but computationally obscure, modulatory effects on learning and cognition. Here, we studied the impact of optogenetic stimulation of dorsal raphe serotonin neurons in mice performing a non-stationary, reward-driven decision-making task. Animals showed two distinct choice strategies. Choices after short inter-trial-intervals (ITIs) depended only on the last trial outcome and followed a win-stay-lose-switch pattern. In contrast, choices after long ITIs reflected outcome history over multiple trials, as described by reinforcement learning models. We found that optogenetic stimulation during a trial significantly boosted the rate of learning that occurred due to the outcome of that trial, but these effects were only exhibited on choices after long ITIs. This suggests that serotonin neurons modulate reinforcement learning rates, and that this influence is masked by alternate, unaffected, decision mechanisms. These results provide insight into the role of serotonin in treating psychiatric disorders, particularly its modulation of neural plasticity and learning.
- Explicit knowledge of task structure is a primary determinant of human model-based actionPublication . Castro-Rodrigues, Pedro; Akam, Thomas; Snorasson, Ivar; Camacho, Marta; Paixão, Vitor; Maia, Ana; Barahona-Corrêa, J. Bernardo; Dayan, Peter; Simpson, H. Blair; Costa, Rui M.; Oliveira-Maia, Albino J.Explicit information obtained through instruction profoundly shapes human choice behaviour. However, this has been studied in computationally simple tasks, and it is unknown how model-based and model-free systems, respectively generating goal-directed and habitual actions, are affected by the absence or presence of instructions. We assessed behaviour in a variant of a computationally more complex decision-making task, before and after providing information about task structure, both in healthy volunteers and in individuals suffering from obsessive-compulsive or other disorders. Initial behaviour was model-free, with rewards directly reinforcing preceding actions. Model-based control, employing predictions of states resulting from each action, emerged with experience in a minority of participants, and less in those with obsessive-compulsive disorder. Providing task structure information strongly increased model-based control, similarly across all groups. Thus, in humans, explicit task structural knowledge is a primary determinant of model-based reinforcement learning and is most readily acquired from instruction rather than experience.