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Hambrick and Engle (2002) proposed 3 models of how domain knowledge and working memory capacity may work together to influence episodic memory: a \"rich-get- richer\" model, a \"building blocks\" model, and a \"compensatory\" model. Their results supported the rich-get- richer model, although later work by Hambrick and Oswald (2005) found support for a building blocks model. We investigated the effects of domain knowledge and working memory on recall of studied grocery prices. Working memory was measured with 3 simple span tasks. A contrast of realistic versus fictitious foods in the episodic memory task served as our manipulation of domain knowledge, because participants could not have domain knowledge of fictitious food prices. There was a strong effect for domain knowledge (realistic food–price pairs were easier to remember) and a moderate effect for working memory capacity (higher working memory capacity produced better recall). Furthermore, the interaction between domain knowledge and working memory produced a small but significant interaction in 1 measure of price recall. This supported the compensatory model and stands in contrast to previous research.

A similar neural ensemble participates in the encoding of two distinct memories, resulting in the recall of one memory increasing the likelihood of recalling the other, but only if those memories occur very closely in time—within a day rather than across a week. Linkage of separate memories across time This paper tests and provides support for the emerging hypothesis that two distinct memories formed close in time may be linked, such that recall of one triggers recall of the other. Using a range of techniques including in vivo calcium imaging with miniature head-mounted fluorescent microscopes in freely behaving mice, Alcino Silva and colleagues show that learning-dependent changes in excitability can temporally and contextually link memories formed close in time. Interestingly the overlap between memory encoding ensembles and strengthening of the second memory within short periods of time do not occur in aged animals, which do not exhibit the increased hippocampal excitability necessary for such links to occur. Recent studies suggest that a shared neural ensemble may link distinct memories encoded close in time 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 . According to the memory allocation hypothesis 1 , 2 , learning triggers a temporary increase in neuronal excitability 13 , 14 , 15 that biases the representation of a subsequent memory to the neuronal ensemble encoding the first memory, such that recall of one memory increases the likelihood of recalling the other memory. Here we show in mice that the overlap between the hippocampal CA1 ensembles activated by two distinct contexts acquired within a day is higher than when they are separated by a week. Several findings indicate that this overlap of neuronal ensembles links two contextual memories. First, fear paired with one context is transferred to a neutral context when the two contexts are acquired within a day but not across a week. Second, the first memory strengthens the second memory within a day but not across a week. Older mice, known to have lower CA1 excitability 15 , 16 , do not show the overlap between ensembles, the transfer of fear between contexts, or the strengthening of the second memory. Finally, in aged mice, increasing cellular excitability and activating a common ensemble of CA1 neurons during two distinct context exposures rescued the deficit in linking memories. Taken together, these findings demonstrate that contextual memories encoded close in time are linked by directing storage into overlapping ensembles. Alteration of these processes by ageing could affect the temporal structure of memories, thus impairing efficient recall of related information.

People remember emotional and taboo words better than neutral words. It is well known that words that are processed at a deep (i.e., semantic) level are recalled better than words processed at a shallow (i.e., purely visual) level. To determine how depth of processing influences recall of emotional and taboo words, a levels of processing paradigm was used. Whether this effect holds for emotional and taboo words has not been previously investigated. Two experiments demonstrated that taboo and emotional words benefit less from deep processing than do neutral words. This is consistent with the proposal that memories for taboo and emotional words are a function of the arousal level they evoke, even under shallow encoding conditions. Recall was higher for taboo words, even when taboo words were cued to be recalled after neutral and emotional words. The superiority of taboo word recall is consistent with cognitive neuroscience and brain imaging research.

Research on episodic memory has established that spontaneous eye movements occur to spaces associated with retrieved information even if those spaces are blank at the time of retrieval. Although it has been claimed that such looks to \"nothing\" can function as facilitatory retrieval cues, there is currently no conclusive evidence for such an effect. In the present study, we addressed this fundamental issue using four direct eye manipulations in the retrieval phase of an episodic memory task: (a) free viewing on a blank screen, (b) maintaining central fixation, (c) looking inside a square congruent with the location of the to-be-recalled objects, and (d) looking inside a square incongruent with the location of the to-be-recalled objects. Our results provide novel evidence of an active and facilitatory role of gaze position during memory retrieval and demonstrate that memory for the spatial relationship between objects is more readily affected than memory for intrinsic object features.

To make decisions, animals must evaluate candidate choices by accessing memories of relevant experiences. Yet little is known about which experiences are considered or ignored during deliberation, which ultimately governs choice. We propose a normative theory predicting which memories should be accessed at each moment to optimize future decisions. Using nonlocal ‘replay’ of spatial locations in hippocampus as a window into memory access, we simulate a spatial navigation task in which an agent accesses memories of locations sequentially, ordered by utility: how much extra reward would be earned due to better choices. This prioritization balances two desiderata: the need to evaluate imminent choices versus the gain from propagating newly encountered information to preceding locations. Our theory offers a simple explanation for numerous findings about place cells; unifies seemingly disparate proposed functions of replay including planning, learning, and consolidation; and posits a mechanism whose dysfunction may underlie pathologies like rumination and craving.

Two studies examined whether photographing objects impacts what is remembered about them. Participants were led on a guided tour of an art museum and were directed to observe some objects and to photograph others. Results showed a photo-taking-impairment effect: If participants took a photo of each object as a whole, they remembered fewer objects and remembered fewer details about the objects and the objects' locations in the museum than if they instead only observed the objects and did not photograph them. However, when participants zoomed in to photograph a specific part of the object, their subsequent recognition and detail memory was not impaired, and, in fact, memory for features that were not zoomed in on was just as strong as memory for features that were zoomed in on. This finding highlights key differences between people's memory and the camera's \"memory\" and suggests that the additional attentional and cognitive processes engaged by this focused activity can eliminate the photo-taking-impairment effect.

How are new experiences transformed into memories? Recent findings have shown that activation in brain regions involved in the initial task performance reemerges during postlearning rest, suggesting that \"offline activity\" might be important for this transformation. It is unclear, however, whether such offline activity indeed reflects reactivation of individual learning experiences, whether the amount of event-specific reactivation is directly related to later memory performance, and what brain regions support such event-specific reactivation. Here, we used functional magnetic resonance imaging to assess whether event-specific reactivation occurs spontaneously during an active, postlearning delay period in the human brain. Applying representational similarity analysis, we found that successful recall of individual study events was predicted by the degree of their endogenous reactivation during the delay period. Within the medial temporal lobe, this reactivation was observed in the entorhinal cortex. Beyond the medial temporal lobe, event-specific reactivation was found in the retrosplenial cortex. Controlling for the levels of blood oxygen level-dependent activation and the serial position during encoding, the data suggest that offline reactivation might be a key mechanism for bolstering episodic memory beyond initial study processes. These results open a unique avenue for the systematic investigation of reactivation and consolidation of episodic memories in humans.

During the past decade, a large body of research has shown that memory traces can become labile upon retrieval and must be restabilized. Critically, interrupting this reconsolidation process can abolish a previously stable memory. Although a large number of studies have demonstrated this reconsolidation associated amnesia in nonhuman animals, the evidence for its occurrence in humans is far less compelling, especially with regard to declarative memory. In fact, reactivating a declarative memory often makes it more robust and less susceptible to subsequent disruptions. Here we show that existing declarative memories can be selectively impaired by using a noninvasive retrieval–relearning technique. In six experiments, we show that this reconsolidation-associated amnesia can be achieved 48 h after formation of the original memory, but only if relearning occurred soon after retrieval. Furthermore, the amnesic effect persists for at least 24 h, cannot be attributed solely to source confusion and is attainable only when relearning targets specific existing memories for impairment. These results demonstrate that human declarative memory can be selectively rewritten during reconsolidation.