Hippocampal lesions facilitate instrumental learning with delayed reinforcement but induce impulsive choice in rats |
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Authors: | Timothy?HC?Cheung Email author" target="_blank">Rudolf?N?CardinalEmail author |
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Institution: | (1) Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge, CB2 3EB, UK;(2) Psychopharmacology Section, Division of Psychiatry, B Floor, Medical School, Queen's Medical Centre, Nottingham, NG7 2UH, UK |
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Abstract: | Background Animals must frequently act to influence the world even when the reinforcing outcomes of their actions are delayed. Learning
with action-outcome delays is a complex problem, and little is known of the neural mechanisms that bridge such delays. When
outcomes are delayed, they may be attributed to (or associated with) the action that caused them, or mistakenly attributed
to other stimuli, such as the environmental context. Consequently, animals that are poor at forming context-outcome associations
might learn action-outcome associations better with delayed reinforcement than normal animals. The hippocampus contributes
to the representation of environmental context, being required for aspects of contextual conditioning. We therefore hypothesized
that animals with hippocampal lesions would be better than normal animals at learning to act on the basis of delayed reinforcement.
We tested the ability of hippocampal-lesioned rats to learn a free-operant instrumental response using delayed reinforcement,
and what is potentially a related ability – the ability to exhibit self-controlled choice, or to sacrifice an immediate, small
reward in order to obtain a delayed but larger reward. |
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Keywords: | |
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