Effects of MK-801 on vicarious trial-and-error and reversal of olfactory discrimination learning in weanling rats

The effects of dizocilpine maleate (MK-801) on vicarious trial-and-error (V TE), and on simultaneous olfactory discrimination learning and its reversal , were observed in weanling rats. The term VTE was used by Tolman (The dete rminers of behavior at a choice point. Psychol. Rev. 1938,46:318-336), who described it as conflict-like behavior at a choice-point in simultaneous di scrimination learning. It takes the form of head movements from one stimulu s to the other, and has recently been proposed by Amsel (Hippncampal functi on in the rat: cognitive mapping or vicarious trial-and-error? Hippocampus, 1993;3:251-256) as related to hippocampal, nonspatial function during this learning. Weanling male rats received systemic MK-801 either 30 min before the onset of olfactory discrimination training and its reversal, or only b efore its reversal. The MK-801-treated animals needed significantly more se ssions to acquire the discrimination and showed significantly fewer VTEs in the acquisition phase of learning. Impaired reversal learning was shown on ly when MK-801 was administered during the reversal-learning phase, itself, and not when it was administered throughout both phases. (C) 1998 Elsevier Science B.V. All rights reserved.