To investigate the role of the hippocampus in visual memory function in participants with idiopathic generalized epilepsy (pwIGE).

Compared to healthy controls without epilepsy, pwIGE exhibit worse performance on memory tests. The hippocampus is vital for memory function and activated by the scene-encoding task (SET) during functional magnetic resonance imaging (fMRI). We hypothesized that increased hippocampus activation during SET fMRI would be associated with better memory performance in pwIGE.

A two-condition SET was administered to pwIGE during a 3-Tesla fMRI scan. In the Scene condition, they were displayed scenes and instructed to indicate if indoor or outdoor via button press and to remember the scenes (targets) for a post-scan test. In the Match condition, they were displayed side-by-side images and instructed to determine if images were similar or dissimilar. In-scanner and post-scan accuracy were collected, and fMRI data were analyzed using AFNI. A Pearson correlation was used to determine the relationship between SET fMRI activation (one sample t-test: Scene>Match) and post-scan target accuracy.

Sixteen pwIGE (8 female; mean age of 28) completed SET fMRI; mean epilepsy onset age was 15, and 9 (56%) seizure-free (self-reported for all seizure types) for the past 6 months. Participants with active seizures experienced an average of 1.43 seizures/month. In-scanner accuracy was 70.59% for Scene and 68.63% for Match conditions. Post-scan accuracy was 55.49% for target and 65.51% for foil scenes. SET fMRI group analysis indicated significant activation (Scene>Match) in both left and right hippocampi during scene encoding (corrected p<0.05). Left hippocampus fMRI activation was significantly correlated with post-scan target recognition accuracy (r=0.602, p=0.018), which was not evident for the right hippocampus (r=0.304, p=0.271).

In pwIGE, increased left hippocampal activity during visual memory encoding is associated with increased visual memory performance. Future directions include examining effects of seizure control status in a larger sample.