O-15-butanol PET activation study on declarative memory

Aim: In this study, neuroanatomical correlates of encoding and retrieval in paired associate learning were evaluated with positron emission tomography using auditorily presented highly imaginable words. Methods: Six right-han ded normal male volunteers took part in the study. Each subject underwent s ix O-15-butanol PET scans. On each of the six trials the memory task began with the injection of a bolus of O-15-butanol. The subjects had to learn an d retrieve twelve word pairs (highly imaginable words, not semantically rel ated). The presentation of nonsense words served as reference condition. Re sults: Recall accuracy after 2-4 presentations was high during the PET meas urement. In both encoding and retrieval we found anterior cingulate activat ion. We show bilateral dorsolateral prefrontal activation during the encodi ng of auditorily presented word pair associates, whereas retrieval led to l eft frontal activation. Furthermore, we demonstrate the importance of the p recuneus in the retrieval of highly imaginable word-pair associates. Conclu sion: Our results support the hypothesis of the presence of distributed wid espread brain structures subserving episodic declarative memory.