At present studies investigate the relationship between memory and hippocampus with functional neuroimaging [2]. The morphometric magnetic resonance imaging approach was often performed to understand the pathology and the decrease of the performances. In our study we showed the evidence that this latter technique should give us interesting informations about memory processing on healthy subjects. The purpose of this research was to study the relationship between an explicit (EM) and implicit (IM) memory test and the hippocampal volume.

Seventy healthy adults were administered an established test of explicit and implicit memory: the word stem completion. A magnetic resonance imaging was performed for each subject on a 1.5 T signa unit (General Electric). The volumetric acquisitions were obtained with a spoiled gradient recalled acquisition at the steady state sequence (GRASS). Parameters of the sequence were 23/5/35/1; field of view was 22 cm, and matrix size 256x192. One hundred twenty-four contiguous sections were obtained of the entire head. To obtain measurements of the volume of the hippocampal formations, an accurate 3-D processing technique was used to segment the hippocampus [1].

There was a significant negative correlation between the EM test and both hippocampal volumes. The IM test did not correlate with hippocampal volume and total brain volume. These data indicated that MRI morphometric techniques were relevant not only for studying pathology but also for neuropsychological studies on healthy subjects.

References

1. Hasboun, D.; Chantome, M.; Zouaoui, A.; Sahel, M., Deladoeuille, M.; Sourour, N.; Duyme, M.; Baulac, M.; Marsault, C.; Dormont, D. (1996). MR determination of hippocampal volume: comparison of three methods. American Journal of Neuroradiology, 17, 1091-1098.
2. Squire, L.R.; Ojemann, J.; Miezin, F.; Petersen, S.; Videen, T.; Raichle, M. (1992). Activation of the hippocampus in normal humans: a functional anatomical study of memory. Proceedings of the National Academy of Science of the U.S.A., 89, 1837-1841.