A common functional brain network for autobiographical, episodic, and semantic memory retrieval.

The objective of this study was to delineate a common functional network that underlies autobiographical, episodic, and semantic memory retrieval. We conducted an event-related fMRI study in which we utilized the same pictorial stimuli, but manipulated retrieval demands to extract autobiographical, episodic, or semantic memories. To assess this common network, we first examined the functional connectivity of regions identified by a previous analysis of task-related activity that were active across all three tasks. Three of these regions (left hippocampus, left lingual gyrus, and right caudate nucleus) appeared to share a common pattern of connectivity. This was confirmed in a subsequent functional connectivity analysis using these three regions as seeds. The results of this analysis showed that there was a pattern of functional connectivity that characterized all three seeds and that was common across the three retrieval conditions. Activity in inferior frontal and middle temporal cortex bilaterally, left temporoparietal junction, and anterior and posterior cingulate gyri was positively correlated with the seeds, whereas activity in posterior occipito-temporo-parietal regions was negatively correlated. These findings support the idea that a common neural network underlies the retrieval of declarative memories regardless of memory content. This proposed network consists of increased activity in regions that represent internal processes of memory retrieval and decreased activity in regions that mediate attention to external stimuli.