Retrieval Search and Strength Evoke Dissociable Brain Activity during Episodic Memory Recall

Abstract

Neuroimaging studies of episodic memory retrieval have revealed activations in the human frontal, parietal, and medial-temporal lobes that are associated with memory strength. However, it remains unclear whether these brain responses are veritable signals of memory strength or are instead regulated by concomitant subcomponents of retrieval such as retrieval effort or mental search. This study used event-related fMRI during cued recall of previously memorized word-pair associates to dissociate brain responses modulated by memory search from those modulated by the strength of a recalled memory. Search-related deactivations, dissociated from activity due to memory strength, were observed in regions of the default network, whereas distinctly strength-dependent activations were present in superior and inferior parietal and dorsolateral PFC. Both search and strength regulated activity in dorsal anterior cingulate and anterior insula. These findings suggest that, although highly correlated and partially subserved by overlapping cognitive control mechanisms, search and memory strength engage dissociable regions of frontoparietal attention and default networks.

The effects of sleep on the neural correlates of pattern separation

“…While we did not explicitly measure memory strength, accuracy and reaction time data are consistent with low memory strength in the delay conditions of the current study. According to this interpretation, our results of greater activation when memory strength is the lowest are consistent with those of Reas and Brewer () in the DLPFC and dorsal ACC (though not in the inferior parietal lobule).…”

“…Reas and Brewer () showed that DLPFC, dorsal ACC (in a region similarly located to our medial frontal cortical activation), and inferior parietal lobule all respond differentially to memory strength and memory search in recognition memory. Reas and Brewer demonstrated that activation in dorsal ACC increased during memory search and was further modulated by memory strength (with greatest activation in the “low” strength condition).…”

Phases of learning: How skill acquisition impacts cognitive processing

“…Such work agrees with our findings that the involvement of frontal regions during Encoding stage diminishes with practice. Furthermore, fMRI studies have found reduction in the activation of the left dorsal lateral prefrontal cortex (Reas & Brewer, 2013) and left lateral prefrontal cortex (Cabeza, Locantore, & Anderson, 2003) as retrieval becomes easier; however, the diverse functions performed by these regions make it difficult to know the exact role of these regions in memory recall.…”

Neurocognitive mechanisms of the “testing effect”: A review

“…They found that activity in the IPL decreased from the immediate to the delayed test for restudied items but not for items that were tested during practice. Since one hypothesis concerning the level of activation in the IPL is that it might reflect the strength or richness of retrieved representations [35,36], the comparably stable activation level over time for tested items might indicate that practice-testing made memory traces more resistant to decay than restudying.…”