Abstract
IntroductionWe used dynamic causal modeling (DCM) to examine effective connectivity during cued autobiographical memory (AM) search in a left‐hemispheric network consisting of six major regions within the large network of brain regions recruited during memory retrieval processes.MethodsFunctional MRI data were acquired while participants were shown verbal cues describing common life events and requested to search for a personal memory associated with the cue. We examined directed couplings between the ventromedial (vmPFC), dorsomedial (dmPFC), and dorsolateral prefrontal cortices (dlPFC), hippocampus, angular gyrus, and the posterior midline cortex (RSC/PCC/Prec).ResultsDuring AM search, the vmPFC, dlPFC, and RSC/PCC/Prec acted as primary drivers of activity in the rest of the network. Moreover, when AM search completed successfully (Hits), the effective connectivity of the hippocampus on the vmPFC and angular gyrus was up‐modulated. Likewise, there was an increase in the influence of the RSC/PCC/Prec in the activity of the dlPFC and dmPFC. Further analysis indicated that the modulation observed during Hits is primarily a distributed phenomenon that relies on the interplay between different brain regions.ConclusionThese results suggest that prefrontal and posterior midline cortical regions together with the dlPFC largely coordinate the processes underlying AM search, setting up the conditions on which the angular gyrus and the hippocampus may act upon when the outcome of the search is successful.
Highlights
Autobiographical memories (AM) retrieval, i.e., when memories of personally experienced events are brought to recollection, is known to engage a large ensemble of brain regions (Cabeza and St Jacques, 2007; Svoboda et al, 2006), most notably the ventral and dorsal aspects of the medial prefrontal cortex, the lateral prefrontal cortex, 22 the posterior medial cortex, likely encompassing portions of the posterior cingulate cortex (PCC), the precuneus and the retrosplenial cortex (RSC), the medial temporal 2 lobes, and the lateral parietal cortex
Here we focused the analysis in regions along the frontal and posterior (RSC/PCC/Prec) midline cortices, which mostly overlap with the default-mode network, regions involved with attention and cognitive control, and the hippocampus
dynamic causal modeling (DCM) results (Section 3.3) showed that the RSC/PCC/Prec, 2 dorsolateral prefrontal cortices (dlPFC) and ventromedial prefrontal cortex (vmPFC) were the only nodes that positively influenced the activity in the rest 3 of the nodes via endogenous connections, suggesting that they serve as a primary 4 backbone structure supporting Autobiographical memory (AM) search processes
Summary
Autobiographical memories (AM) retrieval, i.e., when memories of personally experienced events are brought to recollection, is known to engage a large ensemble of brain regions (Cabeza and St Jacques, 2007; Svoboda et al, 2006), most notably the ventral and dorsal aspects of the medial prefrontal cortex, the lateral prefrontal cortex, 22 the posterior medial cortex, likely encompassing portions of the posterior cingulate cortex (PCC), the precuneus and the retrosplenial cortex (RSC), the medial temporal 2 lobes, and the lateral parietal cortex. Results pointed out to the existence of a medial temporal lobe network, encompassing regions that are typically associated with memory retrieval processes such as ventromedial prefrontal cortex (vmPFC), hippocampus, and parahippocampus, which influenced the medial PFC network during memory search but only in the trials where the retrieved AM was more accessible (i.e., when participants were able to quickly find a memory associated with the cue). These results highlight first and foremost the involvement of widely distributed brain networks during the performance of AM retrieval. How regions within and between such large networks interact with one another during AM retrieval processes still remains to be clarified
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