We present neuroanatomical correlates of encoding and retrieval in an episo
dic memory task using visually presented highly imaginable word-pair associ
ates. A total of 13 right-handed normal male volunteers took part in the st
udy. Each subject underwent six O-15-butanol PET scans. On each of the six
trials the memory task began 30 s before the injection of a bolus of O-15-b
utanol. The subjects had to learn and retrieve 12 word pairs (highly imagin
able words, not semantically related, hard associations). The presentation
of nonsense words served as a reference condition. Recall accuracy after 2-
4 presentations was 66.1% +/- 21.1 correct during the PET measurement so th
at scanning during the retrieval of word pair associates was appropriate to
capture the brain activity associated with retrieval. The results obtained
support the hypothesis of the presence of an asymmetric network consisting
of distributed brain structures subserving associative memory. We show lef
t dorsolateral prefrontal activation during the encoding of visually presen
ted word pair associates, whereas retrieval led to bilateral frontal activa
tion. Furthermore, the importance of the precuneus in the retrieval of high
ly imaginable word-pair associates using visual imagery as a mnemonic strat
egy is demonstrated. (C) 1998 Elsevier Science B.V. All rights reserved.