Adaptive Stimulus Representations: A Computational Theory of Hippocampal-Region Functions

We present a theory of cortico-hippocampal interaction in discrimination learning. The hippocampal region is presumed to form new stimulus representations which facilitate learning by enhancing the discriminability of predictive stimuli and compressing stimulus-stimulus redundancies. The cortical and cerebellar regions, which are the sites of long-term memory. may acquire these new representations but are not assumed to be capable of forming new representations themselves. Instantiated as a connectionist model. this theory accounts for a wide range of trial-level classical conditioning phenomena in normal (intact) and hippocampal-lesioned animals. It also makes several novel predictions which remain to be investigated empirically. The theory implies that the hippocampal region is involved in even the simplest learning tasks; although hippocampal-lesioned animals may be able to use other strategies to learn these tasks. the theory predicts that they will show consistently different patterns of transfer and generalization when the task demands change.