Reassessing hippocampal contributions to implicit memory: a call for conceptual clarity, methodological rigor, and increased measures of awareness

In a previous discussion paper, we conducted a systematic review of 13 implicit memory studies that reported fMRI activity in the hippocampus. It was determined that each of these studies suffered from at least one of the following confounds that could produce hippocampal activity: explicit memory contamination, imbalanced attentional states, imbalanced stimuli between conditions, or differential novelty. Thus, we concluded that implicit memory is not associated with the hippocampus. Six commentaries on that discussion paper were received from Hannula (2024), Henke and Ruch (2024), Rosenthal (2024), Spaak (2024), Thakral et al. (2024), and Züst (2024). In this response, we address several issues to clarify our theoretical and experimental framework and maintain that when confounds are excluded, there is no evidence for hippocampal involvement during implicit memory. This discourse highlights the need for conceptual clarity, methodological consistency, and the critical distinction between neural engagement and behavioral expression.