The involvement of distributed brain regions in declarative memory has been
hypothesized based on studies with verbal memory tasks. To characterize ep
isodic declarative memory function further, 14 right-handed volunteers perf
ormed a visual verbal learning task using paired word associates. The volun
teers underwent positron emission tomography. O-15-butanol was used as a tr
acer of regional cerebral blood flow (rCBF). Inter-regional functional inte
ractions were assessed based on within-task, across-subject interregional r
CBF correlations. Anatomical connections between brain areas were based on
known anatomy. Structural equation modelling was used to calculate the path
coefficients representing the magnitudes of the functional influences of e
ach area on the ones to which it is connected by anatomical pathways. The e
ncoding and the retrieval network elicit similarities in a general manner b
ut also differences. Strong functional linkages involving visual integratio
n areas, parahippocampal regions, left precuneus and cingulate gyrus were f
ound in both encoding and retrieval; the functional linkages between poster
ior regions and prefrontal regions were more closely linked during encoding
, whereas functional linkages between the left parahippocampal region and p
osterior cingulate as well as extrastriate areas and posterior cingulate gy
rus were stronger during retrieval. In conclusion, these findings support t
he idea of a global bihemispheric, asymmetric encoding/retrieval network su
bserving episodic declarative memory. Our results further underline the rol
e of the precuneus in episodic memory, not only during retrieval but also d
uring encoding.