Browsing by Author "Costa, Rui M."
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- 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.
- Postingestive Modulation of Food Seeking Depends on Vagus-Mediated Dopamine Neuron ActivityPublication . Fernandes, Ana B.; Alves da Silva, Joaquim; Almeida, Joana; Cui, Guohong; Gerfen, Charles R.; Costa, Rui M.; Oliveira-Maia, Albino J.Postingestive nutrient sensing can induce food preferences. However, much less is known about the ability of postingestive signals to modulate food-seeking behaviors. Here we report a causal connection between postingestive sucrose sensing and vagus-mediated dopamine neuron activity in the ventral tegmental area (VTA), supporting food seeking. The activity of VTA dopamine neurons increases significantly after administration of intragastric sucrose, and deletion of the NMDA receptor in these neurons, which affects bursting and plasticity, abolishes lever pressing for postingestive sucrose delivery. Furthermore, lesions of the hepatic branch of the vagus nerve significantly impair postingestive-dependent VTA dopamine neuron activity and food seeking, whereas optogenetic stimulation of left vagus nerve neurons significantly increases VTA dopamine neuron activity. These data establish a necessary role of vagus-mediated dopamine neuron activity in postingestive-dependent food seeking, which is independent of taste signaling.