Academic journal article Psychonomic Bulletin & Review

Transfer of Memory Retrieval Cues in Rats

Academic journal article Psychonomic Bulletin & Review

Transfer of Memory Retrieval Cues in Rats

Article excerpt

Two experiments using rats were conducted to determine whether the retrieval of a memory could be brought under the control of new contextual cues that had not been present at the time of training. In Experiment 1, rats were trained in one context and then exposed to different contextual cues immediately, 60 min, or 120 min after training. When tested in the shifted context, rats that had been exposed shortly after training treated the shifted context as if it were the original context. The control that the previously neutral context had over retrieval disappeared with longer posttraining delays, suggesting the importance of an active memory representation during exposure. Experiment 2 replicated the basic finding and demonstrated that the transfer of retrieval cues was specific to the contextual cues present during exposure. These findings with rats are consistent with findings from infant research (see, e.g., Boller & Rovee-Collier, 1992) that have shown that a neutral context can come to serve as a retrieval cue for an episode experienced elsewhere.

Transfer of control over responding has typically focused on Pavlovian instrumental interactions (Domjan, 2003). Solomon and Turner's ( 1 962) classic study provides a pertinent example. Dogs trained in a shuttle box to avoid a light later received, in a different apparatus, Pavlovian fear conditioning in which a tone was paired with a brief but inescapable shock. Subsequently, when returned to the shuttle apparatus, the dogs made avoidance responses to the tone; that is, the control over avoidance had transferred to the Pavlovian cue.

In Solomon and Turner's (1962) study, transfer depended on direct pairing of a signal (tone) with the shock. More recently, there has been growing interest hi memory representations and conditioning (see, e.g., Dwyer, Mackintosh, & Boakes, 1998; Rescorla, 1973, 1974). In these paradigms, the physical cue is absent at the time of a manipulation; thus, any changes in behavior are presumably attributable to a memory representation. By and large, such studies have focused on altering the value of the conditioned stimulus (CS) by virtue of changes in an unconditioned stimulus in the presence of a representation of the CS. In contrast, little attention has been given to the issue from a memory retrieval perspective: Can a neutral stimulus or contextual cue paired with the representation of a learning episode gain retrieval control over responding?

One approach to this issue takes advantage of the observation that performance is commonly impaired when subjects are tested in a context different from that used at training. This context shift effect, found in both human and animal studies (see, e.g., Boiler & Rovee-Collier, 1992; Godden & Baddeley, 1975; Gordon, McCracken, DessBeech, & Mowrer, 1981; Smith, 1979; Zhou & Riccio, 1996), is typically attributed to a memory deficit resulting from the removal of retrieval cues. In one of the few studies focusing on memory transfer, Boiler and RoveeCollier (1992) trained 6-month-old infants to kick a leg to activate a mobile and then immediately exposed them to a novel context (crib liner). At testing, the infants responded in the new context as if it were the training context. Thus, the memory was apparently receded into the context present while the memory was active.

Although the temporal relationship between training and exposure to the new context was not manipulated hi that study, later work using a retroactive interference paradigm demonstrated that the effect of exposure decreased with longer delays (Rossi-George & Rovee-Collier, 1 999). This outcome is consistent with the many findings showing that the severity of retrograde amnesia is inversely related to the interval between training and the amnesic insult. The time-dependent gradient of amnesia is often viewed as resulting from disruption of consolidation - that is, a putative storage process but an alternative retrieval-oriented view is conceptually more compatible with the Rovee-Collier findings (Hinderliter, Webster, & Riccio, 1975; Riccio, Millin, & Gisquet- Verrier, 2003; Riccio, Moody, & Millin, 2002). …

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