In a pair of experiments, we have compared the ability of changes of place (Exp. 1) and changes of time of day (Exp. 2) to separately modulate learned saline-aversion memory phenomena in rats. Neither a spatial nor a temporal change disrupted latent inhibition using the present behavioral procedure. However, pre-exposure to the taste increased the contextual control of the learned aversion expression. The aversion reappeared in the place or at the time of conditioning after extinction in a different context. The results indicate that environmental and temporal contexts can independently, but similarly modulate taste aversion learning.Context is an often loosely defined term, which in neuroscience is becoming more common, especially with the current interest to investigate the neural bases of episodic memory in humans (Nadel et al 1985;Schacter and Tulving 1994) and to search for equivalent memory phenomena in nonhuman animals (Clayton and Dickinson 1998;Aggleton and Brown 1999). Whereas rats readily associate tastes of substances with their visceral consequences (García and Koelling 1966;García et al. 1968;Bures et al. 1998;Bernstein 1999), contextual cues also modulate conditioned taste aversions (CTA), because the context specificity, both of the expression (Boakes et al. 1997;Archer et al. 1979Archer et al. , 1980Jarbe et al. 1986;Puente et al. 1988;Bonardi et al. 1990;Loy et al. 1993) and extinction (Rosas and Bouton 1997;Archer et al. 1979) of a learned aversion, and of the latent inhibition (LI) of CTA (Rudy et al. 1977;Hall and Channell 1986) has been reported. In CTA studies, context frequently refers to a particular place that may combine a variety of external environmental cues. However, a broad definition of context may include not only external, but also internal, background cues and a sense of time (Bouton 1993;Pearce and Bouton 2001). Very few of the above-cited studies reporting context modulation of CTA have included the time of day as part of the context, either purposely (Rosas and Bouton 1997) or as the outcome of applying two daily drinking sessions (Hall and Channell 1986;Bonardi et al. 1990). Moreover, although the possibility that the time of day may itself form a context is supported by a recent report showing a time-of-day-dependent expression of the behavioral sensitization to amphetamine (Arvanitogiannis et al. 2000), to our knowledge, no study has explored the ability of the time of day to modulate CTA independently of the spatial context.In the present experiments, we specifically examine whether spatial (Exp. 1) and temporal (Exp. 2) contextual cues separately modulate learned saline-aversion memory phenomema. In Experiment 1, two different sized and shaped cages were used as contexts (Fig. 1). The environments differed in location, geometry, visual, auditory, and tactile cues. In Experiment 2, two different times during the illumination cycle were used as temporal contexts. To differentiate them as much as possible, morning (10:00) and evening (20:00) drinking sessions were used. E...
