Exploring the neural bases of episodic and semantic memory: the role of structural and functional neuroimaging

Exploration of the neural bases of episodic and semantic memory is best pur sued through the combined examination of the effects of identified lesions on memory and functional neuroimaging of both normal people and patients wh en they engage in memory processing of various kinds. Both structural and f unctional neuroiniaging acquisition and analysis techniques have developed rapidly and will continue to do so. This review briefly outlines the histor y of neuroimaging as it impacts on memory research. Next, what has been lea rned so far from lesion-based research is outlined with emphasis on areas o f disagreement as well as agreement. What has been learned from functional neuroimaging, particularly emission tomography and functional magnetic reso nance imaging, is then discussed, and some stress is placed on topics where the interpretation of imaging studies has so far been unclear. Finally, ho w functional and structural imaging techniques can be optimally used to hel p resolve three areas of disagreement in the lesion literature will be disc ussed. These disagreements concern what the hippocampus and perirhinal cort ex contribute to memory; whether any form of priming depends on the medial temporal lobes; and whether remote episodic as well as semantic memories ce ase to depend on the medial temporal lobes. Although the discussion will sh ow the value of imaging techniques, it will also emphasize some of the limi tations of current neuroimaging studies. (C) 2001 Published by Elsevier Sci ence Ltd.