Lower Levels of Task-Induced Hippocampal Activation Predict Better Performance on a Separate Verbal Memory Evaluation

Inter-individual differences in learning-related activation in the hippocampus and its subregions predict specific differences in memory abilities. The complexity of these relationships creates a setting that is ripe for theoretically informative investigation, but that can also yield reports of spurious relationships that do not reflect underlying neurobiological associations. Across-study replication is therefore a critical step toward understanding how individual differences in hippocampal activity drive individual differences in memory ability. In the domain of verbal memory, Wig et al. (2008) identified a negative relationship between task-induced activation in right posterior HPC (pHPC) and out-of-scanner verbal memory test performance. Replicating this result in an independent sample of 86 participants, we identified the same negative correlation between pHPC activation during an in-scanner Lithuanian-English paired associate learning task and out-of-scanner California Verbal Learning Test (CVLT-II) performance. In a follow-up exploratory voxel-wise association analysis, we observed the same negative correlation between CVLT-II performance and task-induced activity across three regions of the medial temporal lobe: the left perirhinal/entorhinal cortex, right parahippocampal gyrus, and left posterior hippocampus. This replication and accompanying extension represent a critical step toward understanding how pHPC supports verbal memory by answering basic questions concerning the reliability and selectivity of this previously identified relationship.