Activity in the left angular gyrus tracks recollection and prior knowledge

Separate lines of evidence from human neuroimaging have implicated the left angular gyrus (AG) in our ability to recollect specific past episodes and our ability to access general prior knowledge. This poses an important question regarding the nature of the mnemonic content tracked by the left AG: is this region sensitive to recollection, prior knowledge, or overall mnemonic content from either source? In this dissertation, I report three experiments that examine the interplay between recollection and prior knowledge in behaviour and in the univariate activity of the left AG. I argue that the anatomical position of the left AG, as a region of heteromodal association cortex, would predict an integrative role in tracking both types of mnemonic content simultaneously. Chapter 2 describes a series of behavioural studies examining whether general prior knowledge can support task-specific recollection. Participants performed a recognition task on famous and non-famous faces using the remember-know paradigm. The availability of prior knowledge at encoding (i.e., fame) was found to significantly improve recollection, highlighting their interplay. Chapter 3 describes a functional magnetic resonance imaging (fMRI) study testing whether the left AG was sensitive to prior knowledge and recollection within the same individuals. Region PGp of the left AG was sensitive to both recollection and prior knowledge independently at retrieval, and was most strongly recruited when both types of mnemonic content were available simultaneously. Chapter 4 examined the role of the left AG during encoding using subsequent memory for famous and non-famous faces. The left AG (region PGp) showed sensitivity to prior knowledge (i.e., fame) during encoding; unlike retrieval, however, recollection was associated with reduced activity relative to non- recollected trials irrespective of fame. Overall, I argue that these data provide clear evidence that the left AG is primarily driven by processes occurring during retrieval, when we sample existing internal representations from memory as opposed to when we sample the external environment (e.g., encoding). Critically, activity in the left AG is best described as tracking both specific recollections and general prior knowledge, reflecting access to internal mnemonic content irrespective of its relevance to ongoing task performance.Ph.D.2020-11-16 00:00:0