Stimulus configuration, spatial learning, and hippocampal function.

Schmajuk and DiCarlo (Psychol. Rev., 99 (1992) 268-305) introduced a neural network, which utilizes a biologically plausible backpropagation procedure, to describe configural paradigms in classical conditioning. The model correctly describes many experimental results under the assumption that aspiration lesions of the hippocampus eliminate (a) the competition between simple and configural stimuli to gain association with the unconditioned stimulus and (b) the adjustment of initially random configural stimuli. The present study extends the network to describe place learning. Under the assumption that ibotenic acid lesions of the hippocampus only impair the adjustment of initially random configural stimuli, the model correctly shows that ibotenic acid lesions might spare a configural discrimination but impair place learning. In general, the results are taken to support a hippocampal role in the modulation of stimulus configuration.