Anterior Hippocampus Function Used for Predicting Memory Lateralization

Abstract:
Abstract: Using functional magnetic resonance imaging (fMRI) we previously demonstrated bilateral anterior hippocampal activation during a contrast of a visual encoding task with a perceptual discrimination task. The current study was conducted to develop a technique for determining memory lateralization using fMRI. Whole-brain fMRI was performed on fifty neurologically normal controls and twenty-eight temporal lobe epilepsy (TLE) patients (12 left hemisphere TLE; 16 right hemisphere TLE) while encoding pictures of novel scenes or spatially scrambled scenes. Bilateral anterior hippocampal region of interest (ROI) were created by averaging masks drawn on 40 individuals high-resolution anatomy. ROI analyses were applied to each individuals stereotaxically standardized statistical parametric map. The number of voxels exceeding a statistical significance level of p < 0.05 were tallied for both the right and left anterior hippocampal ROIs and used to create a memory laterality index for each subject. Control subjects laterality indexes were normally distributed with a slight bias toward left hemisphere lateralization. Whereas, 11 TLE patients in the right and left side of seizure focus groups had laterality indexes biased away from their respective side of seizure focus. Although postsurgical outcome measures have not been completed, these results are comparable to memory lateralization measures obtained from the WADA test. These results suggest that fMRI may potentially be of use for determining memory lateralization in TLE though further validation is needed.