Contributions of frontal and medial temporal regions to verbal episodic memory: a PET study

Using PET, subtraction and correlation analysis were jointly employed to determine the specific and complementary contributions of frontal and medial temporal regions to verbal episodic encoding and retrieval processes. Subtraction analysis highlighted prefrontal rCBF increases which were predominantly left-sided during intentional encoding and exclusively right-sided during retrieval, the latter being moreover associated with bilateral precuneus activation. However, significant correlation between rCBF values obtained during intentional encoding and performance scores obtained during retrieval concerned, among other regions, the left parahippocampal gyrus, which indicated that the higher the neuronal activity in this medial temporal region during encoding, the better the retrieval performance.