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A biologically inspired model of hippocampal-striatal loops for spatial navigation, path planning, and decision-making| old_uid | 12426 |
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| title | A biologically inspired model of hippocampal-striatal loops for spatial navigation, path planning, and decision-making |
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| start_date | 2013/05/10 |
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| schedule | 13h |
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| online | no |
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| details | Host: Neil Burgess |
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| summary | The hippocampus is known to play a major role in spatial representation, declarative and episodic memory. Neurons in this area fire selectively when the individual is within a small area of the environment. Recently, it has been found in rats that these cells can be active also when the animal is outside the location or context of their corresponding place field, producing so-called "forward sweeps". These typically occur at decision points during task execution and seem to be utilized, among other things, for the evaluation of alternative paths. A similar behavior is found in the ventral striatum, a brain area that is strongly interconnected with the hippocampus and is known to encode value and reward.
In this talk I will describe a biologically inspired neural network that reproduces the hippocampal-ventral striatum circuit. Its core functionality is to implement a goal-directed mechanism of choice, with the hippocampus primarily involved in the mental simulation of possible navigation paths and the ventral striatum involved in the evaluation of the associated reward expectancies. More precisely, decisions about future actions are made by simulating movements and their sensory effects using the same brain areas that are active during overt execution.
The model has been validated in a navigation task in which a rat is placed in a complex maze with multiple rewarding sites. I will show that the rat mentally activates place cells to simulate paths, estimate their value and make decisions, implementing two essential processes of model-based reinforcement learning algorithms of choice: look-ahead prediction and the evaluation of predicted states. Furthermore, as the rat spends more time in the maze, action control slowly switches from goal-directed to habitual behavior, with a decrease of the frequency and depth of mental simulations and a strengthening of stimulus-response like neural activations. |
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| responsibles | Lawrence |
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