Individual-level hippocampal engagement across three fMRI episodic memory-related tasks for presurgical patients

Reliable detection of hippocampal engagement is critical in presurgical memory fMRI, yet the extent to which different paradigms differentially recruit anterior and posterior hippocampal regions at the individual level remains unclear. This study systematically compares hippocampal engagement across three commonly used memory fMRI tasks-autobiographical memory (AUT), picture encoding (PIC) and hometown walking (HTW)- at the individual level, with a particular emphasis on anterior versus posterior hippocampal regions.

A total of 113 presurgical patients completed at least one memory fMRI task (AUT: n = 41; PIC: n = 53; HTW: n = 60). Hippocampal regions of interest were anatomically defined and subdivided into anterior/posterior and ipsilesional/contralesional segments. Individual-level suprathreshold activation detectability of hippocampal ROIs was assessed using standardized statistical criteria (p < 0.01, uncorrected).

All tasks showed high global hippocampal detection rates. However, regional differences were observed in the anterior hippocampus, where AUT demonstrated higher detectability, particularly contralesionally (88.9 %), compared with PIC (60 %) and HTW (64.7 %) (Cramér's V = 0.259). In contrast, posterior hippocampal detection was high and comparable across tasks, with PIC showing the highest rates (80.6-97.8 %). Whole-brain analyses revealed stronger engagement of default mode network regions for AUT.

Memory fMRI paradigms show distinct regional hippocampal engagement profiles and are not interchangeable for presurgical mapping at the individual level. These findings may inform task selection in presurgical memory fMRI depending on the anatomical region of interest and clinical context.