Cued retrieval of memory is typically examined with delay when testing hippocampal functions, as in delayed matching-tosample tasks. Equally emphasized in the literature, on the other hand, is the hippocampal involvement in making arbitrary associations. Paired associate memory tasks are widely used for examining this function. However, the two variables (i.e., delay and paired association) were often mixed in paired associate tasks, and this makes it difficult to localize the cognitive source of deficits with hippocampal perturbation. Specifically, a few studies have recently shown that rats can learn arbitrary paired associations between certain locations and nonspatial items (e.g., object or flavor) and later can retrieve the paired location when cued by the item remotely. Such tasks involve both (1) delay between sampling the cue and retrieving the target location and (2) arbitrary association between the cueing object and its paired location. Here, we tested whether delay was necessary in a cued paired associate task by using a task in which no delay existed between object cueing and the choice of its paired associate. Moreover, fixed associative relationships between the cueing objects and their paired locations were repeatedly used, thus involving no trial-unique association. Nevertheless, inactivations of the dorsal hippocampus with muscimol severely disrupted retrieval of paired associates, whereas the same manipulations did not affect discriminating individual objects or locations. The results powerfully demonstrate that the hippocampus is inherently required for retrieving paired associations between objects and places, and that delay and trial uniqueness of the paired associates are not necessarily required.[Supplemental material is available for this article.]Animal models for testing episodic memory have been particularly useful for studying a selective contribution of the hippocampus and its neural mechanisms. One of the animal models in the literature involves teaching paired associative relationships between mnemonic items and then testing the retrieval of a learned item when cued by its paired associate (Bunsey and Eichenbaum 1993;Day et al. 2003;Kesner et al. 2005). Recently, Day et al. (2003) proposed an impressive rodent version of cued paired associate task, in which rats formed paired associate memory between a particular flavor and its paired associate location. Specifically, in the task, the rat should learn flavor-place paired association during spatial navigation in a sample phase. In the retrieval phase, the rat was cued with one of the flavors learned during the sample phase and was required to navigate to its paired associate place. Compared with other paired associate tasks (Cho and Kesner 1995; Bunsey and Eichenbaum 1996; Lee and Solivan 2008), animals must learn a trial-unique paired association in a single trial in this task. Furthermore, the rat was cued in the start box (thus, away from its original sampling location) during the test phase. Importantly, this feature of the tas...

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