Dentate gyrus-selective colchicine lesion and performance in temporal and spatial tasks

The effects of multiple-site, intradentate, colchicine injections on the performance of a temporal. 'differential reinforcement of low rates of responding' (DRL-20 s) task and a spatial, 'delayed non-matching-to-place' (DNMTP) task in a plus-maze were investigated in rats trained in both tasks prior to the lesion. Quantitative analysis revealed a greater than 86% reduction in the dentate gyrus (DG) of the colchicine-injected rats compared to the sham-operated controls. Dentate gyrus damage rendered rats less efficient than sham-operated controls in the performance of the DRL-20 s task. The DRL inter-response time (IRT) distribution for the DG-lesioned rats and the sham-operated controls was similar; however, while the distribution peak for the control rats was 20 s, it was 16 s for the DG-lesioned rats, indicating that the latter rats underestimated time. Performance of the DG-lesioned rats was also disrupted in the DNMTP task. However, DG-lesioned rats recovered control levels of performance during repeated training with an intertrial interval equal to 3 s. An increase in intertrial interval in lesioned and sham-operated controls disrupted performance in both groups; however, while DG-lesioned rats performed at chance levels when the intertrial interval was increased to 4 min or longer, the sham-operated controls performed at chance levels only when the intertrial interval was increased to 16 min. These results seem most parsimoniously interpreted following the cognitive map theory of hippocampal function. (c) 2004 Elsevier B.V. All rights reserved.