Abstract
Are specific distributed coactivations in the brain during memory retrieval a signature of retrieval outcome? Here we show that this is indeed the case. Widespread brain networks were reported to be involved in the retrieval of long-term episodic memories. Although functional coactivation among particular regions occurs during episodic memory retrieval, it is unknown to what extent it contributes to the accuracy and confidence of recollection. In this study we set out to explore this question. Participants saw a narrative documentary movie. A week later they underwent an fMRI scan during which they either accepted or rejected factual or fictitious verbal statements concerning the movie. Correct vs. incorrect responses to factual statements were more common and were provided with higher confidence than those made to fictitious statements. Whereas activity in the retrieval network correlated mostly with confidence, coactivations primarily correlated with memory accuracy. Specifically, coactivations of left medial temporal lobe regions with temporal and parietal cortices were greater during correct responses to factual statements, but did not differ between responses to fictitious statements. We propose that network coactivations play a role in recovering memory traces that are relevant to online retrieval cues, culminating in distinct retrieval outcomes.
Highlights
The search for the engram (Semon, 1904; Lashley, 1950) is far from completed (Moscovitch, 2007), it is generally accepted that retrieval of long-term memory involves concerted activity of distributed networks (Maguire et al 2000; Frankland and Bontempi, 2005; Moscovitch et al, 2006)
Correct responses to Factual statements were more common than correct answers to Fictitious statements (t(16) = 3.3, p < 0.005), demonstrating that participants were more prone to retrieval errors when presented with Fictitious cues (Fact_incor = 21.1%, Fict_incor = 37.9%; Figure 2A)
When comparing the area under the curve (AUC) of BOLD responses in each regions of interest (ROIs), we found that only a small portion of the retrieval network displayed differential activity as a function of memory performance
Summary
The search for the engram (Semon, 1904; Lashley, 1950) is far from completed (Moscovitch, 2007), it is generally accepted that retrieval of long-term memory involves concerted activity of distributed networks (Maguire et al 2000; Frankland and Bontempi, 2005; Moscovitch et al, 2006). The relevance of such hypothetical coactivity, to memory performance in general and to specific performance attributes in particular is still unknown. MTL-neocortical interactions diminish in patients suffering from degenerative disease, concomitant with impaired memory performance (Greicius et al, 2004; Wang et al, 2006; Supekar et al, 2008; Bai et al, 2009)
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