Rats (Rattus norvegicus) flexibly retrieve objects’ non-spatial and spatial information from their visuospatial working memory: effects of integrated and separate processing of these features in a missing-object recognition task

After being trained to find a previous missing object within an array of four different objects, rats received occasional probe trials with such test arrays rotated from that of their respective three-object study arrays. Only animals exposed to each object’s non-spatial features consistently paired with both its spatial features (feeder’s relative orientation and direction) in the first experiment or with only feeder’s relative orientation in the second experiment (Fixed Configuration groups) were adversely affected by probe trial test array rotations. This effect, however, was less persistent for this group in the second experiment but re-emerged when objects’ non-spatial features were later rendered uninformative. Animals that had both types of each object’s features randomly paired over trials but not between a trial’s study and test array (Varied Configuration groups) were not adversely affected on probe trials but improved their missing-object recognition in the first experiment. These findings suggest that the Fixed Configuration groups had integrated each object’s non-spatial with both (in Experiment 1) or one (in Experiment 2) of its spatial features to construct a single representation that they could not easily compare to any object in a rotated probe test array. The Varied Configuration groups must maintain separate representations of each object’s features to solve this task. This prevented them from exhibiting such adverse effects on rotated probe trial test arrays but enhanced the rats’ missing-object recognition in the first experiment. We discussed how rats’ flexible use (retrieval) of encoded information from their visuospatial working memory corresponds to that of humans’ visuospatial memory in object change detection and complex object recognition tasks. We also discussed how foraging-specific factors may have influenced each group’s performance in this task. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10071-015-0915-8) contains supplementary material, which is available to authorized users.