Episodic memory is defined as a memory system that consciously carries out recollecting one's subjective past experience and re-experiencing it. Through these mental activities, episodic memory is thought to make mental time travel retrospectively and prospectively possible, which is sometimes considered to be unique to humans. However, after a seminal study in scrub-jays by Clayton & Dickinson (1998), animal models of episodic memory have been developing and are starting to affect the concept of human episodic memory itself. This paper will concentrate on reviewing the studies that could encourage nonhuman animals to utilize memory — the properties are consistent with current definition of human episodic memory. Additionally, a discussion on the possibility to divide the system of episodic memory into two sub-processes and to study in animals the sub-processes of episodic memory will be undertaken.

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The mouse is a good animal model that helps us to elucidate various human and other mammalian genetic systems. Several international programs are under way to introduce mutations into every gene in the mouse genome. However, the phenotypes exhibited by every mutant mouse generated in these programs should be determined to reach the goal of these programs. Large-scale phenotyping for genome-wide functional annotation needs efforts by scientists in the infrastructural, logistical, and informatics area. These include the use of standardized procedures for phenotyping and integrated databases with comparable datasets. In this paper, we shall discuss the trends in recent mouse-mutagenesis projects, descriptions of a large amount of phenotyping data from mutants, and descriptions of experimental procedures in an international unified database.

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The present study examined transitive responding and a symbolic distance effect during a transitive inference task in rats. Seven three-step barriers (45 cm high in total) with different visual appearances and tactile features were used as discriminative stimuli. Four rats were trained to choose and climb over one of two barriers presented simultaneously to enter a goal box and get food rewards. If a rat climbed the wrong barrier the door connected to the goal box did not open. All four rats acquired concurrent discrimination learning of four tasks (A+B-, B+C-, C+D-, and D+E-), and showed significant transitive responding to item B on the novel BD pair in a probe test. Moreover, two rats acquired concurrent discrimination learning of six tasks (X+A-, A+B-, B+C-, C+D-, D+E-, and E+F-), and one of them showed a symbolic distance effect, in other words a better performance for novel pairs composed of more distant items (e.g., AE) than pairs composed of closer items (e.g., BD) in the transitive series (X-A-B-C-D-E-F). The symbolic distance effect is regarded as evidence that animals solve transitive inference task based on non-deductive processes, because deductive reasoning predicts better performance to item pairs composed of closer items that call for fewer premises to be combined. Therefore, findings in the present study suggest that, as is the case with birds, monkeys, apes, and human beings, rats seemed to learn a transitive task based on some non deductive processes, such as formation of liner representation of items or value transfer between items.

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