Hippocampal-parietal cortex causal information flow in human episodic memory: replication across three experiments.

While extensive research has focused on hippocampus-prefrontal circuits in episodic memory and spatial navigation, the role of hippocampus-parietal cortex circuits remains understudied. We employed intracranial EEG to investigate these circuits across three different memory experiments, revealing a consistent, asymmetric pattern of higher causal information flow from the hippocampus to both lateral and medial posterior parietal cortex (PPC). This directional information flow was observed during both memory encoding and recall and across verbal and spatial episodic memory domains. Importantly, this directed information flow was not contingent upon activation or suppression states in the hippocampus or PPC. Frequency-specific directional interactions were also identified, with greater hippocampal-to-PPC flow in the delta-theta band and the reverse in the beta band. The robustness of these results was demonstrated through Bayesian replication analysis. Our findings shed new light on the frequency-dependent signaling within hippocampus-parietal circuits, broadening our understanding of their critical roles in human episodic memory.