Recollection and prior knowledge recruit the left angular gyrus during recognition

Abstract The human angular gyrus (AG) is implicated in recollection, or our ability to retrieve detailed memory content from a specific study episode. Parallel work also highlights a key role of the AG in the representation of general knowledge and semantics. How these two lines of research converge remains unclear. The present fMRI experiment used a remember-know paradigm with famous and non-famous faces to test whether activity in the AG could be modulated by both task-specific recollection and general prior knowledge in the same participants. Increased BOLD activity in the left AG was observed during both recollection in the absence of prior knowledge (i.e., recollected > non-recollected or correctly rejected non-famous faces) and when prior knowledge was accessed in the absence of recollection (i.e., famous > non-famous correct rejections). This pattern was unique to the left AG, and was not present in any other regions of the lateral inferior parietal lobe. Furthermore, the response profile of the left AG was consistent with accounts of recollection strength. Recollection-related activity was greater for faces with longer exposures at encoding than those with shorter exposures and was greater for stimuli with prior knowledge than those without, despite prior knowledge being incidental to the recognition decision. Therefore, the left AG is recruited during the access of both task-specific recollection and general prior knowledge, with greater activity as the amount of retrieved information increases, irrespective of its episodic or semantic nature. Significance Statement The human angular gyrus (AG) is often implicated in our ability to remember past events. A separate line of research examining our ability to represent general knowledge has also highlighted the AG as a core region of interest. To reconcile these separate views of AG function, we used fMRI to test whether the human left AG was sensitive to remembering details from a specific study episode (i.e., recollection) or more general prior knowledge, within the same participants. Overall, activity in the left AG was sensitive to both recollection and prior knowledge, suggesting any complete functional account of the left AG during retrieval must consider its sensitivity to both kinds of mnemonic representations.