Memory relationships between MRI volumes and resting PET metabolism of medial temporal lobe structures.

Prior studies of temporal lobe epilepsy (TLE) patients showed that MRI volumes and resting PET scan measures of temporal lobe structures were related to memory. Weintrob and colleagues [Ann. Neurol. 2002;51:442-7] reported that PET glucose uptake in the left perirhinal cortex predicted verbal paired associate (PA) learning, whereas MRI volume of the left hippocampus did not. We investigated whether MRI volumes could account for memory functioning if both PET and volumes were from the same region in 18 TLE patients. Volumes and glucose uptake of the hippocampus and parahippocampal gyrus (PHG) were compared with WMS-III performance. Significant correlations were observed between hippocampal volumes and PA and Logical Memory (LM) Percent Retention, but not between memory and PHG volumes or any PET measures. Multiple regression revealed that hippocampal volumes, but not PHG volumes or PET, significantly predicted PA and LM retention scores. These findings suggest that hippocampal volumes provide unique information regarding memory.