Functional dissociation of striatal and hippocampal cholinergic systems in egocentric and allocentric localization:...

The effects of overtraining on the retention of egocentric localization (EL) and allocentric localization (AL) tasks using rats injected with 1.8 nmol/12 microliters of ethylcholine mustard aziridinium ion (AF64A) in the striatum or hippocampus were examined. In the EL task, an arm positioning at in same direction of a randomly selected start arm was baited throughout trials. In the AL task, a baited arm was fixed throughout trials regardless of the position of the start arm. The performance of EL retention was disrupted only by intrastriatal AF64A injection. The overtrained striatal lesioned animals showed better performance compared to the non-overtrained striatal lesioned animals. In contrast, hippocampal AF64A injection selectively impaired AL retention. Unlike the effect of overtraining on EL retention in striatal lesioned animals, however, the AL performance of hippocampal lesioned animals was not significantly affected by overtraining. The results support the idea of functional dissociation of striatal and hippocampal cholinergic systems in EL and AL learning and provide further evidence that the striatal cholinergic system may be involved in the memory (consolidation or retrieval) process of EL learning, and the hippocampal cholinergic system in the processing of specific cues necessary for efficient performance in AL learning rather than memory.