Neuronal correlates of encoding and retrieval in episodic memory during a paired-word association learning task: a functional magnetic resonance imaging study
Fm. Mottaghy et al., Neuronal correlates of encoding and retrieval in episodic memory during a paired-word association learning task: a functional magnetic resonance imaging study, EXP BRAIN R, 128(3), 1999, pp. 332-342
The investigation of memory function using functional magnetic resonance im
aging (fMRI)) is an expanding field of research. The aim of this study was
to demonstrate brain-activity patterns related to a word-pair association t
ask employing a whole-brain EPI sequence. Six right-handed, healthy male vo
lunteers (mean age: 27.5 years) took part in the study. fMRI was performed
at a field strength of 1.5 Tesla with 26-32 slices parallel to the AC-PC li
ne, depending on individual brain size. Distributed brain regions were acti
vated in episodic encoding and retrieval with similarities, but also (disti
nct) differences in activation patterns. Bilateral prefrontal cortical area
s were involved when comparing encoding as well as retrieval to the referen
ce condition (nonsense words). Furthermore, activation was observed in cere
bellar areas during encoding, and activation in bilateral parietal areas (p
recuneus and inferior parietal cortex) was differentially more pronounced d
uring retrieval. The activation of left dorsomedial thalamus during retriev
al of high imagery-content word-pair associates may point to the role of th
is structure in episodic retrieval. The direct cognitive subtraction of enc
oding minus retrieval yielded a differentially larger left prefrontal activ
ation. There was a differentially higher right prefrontal activation during
retrieval than during encoding, underlining the proposed right/left asymme
try for episodic memory processes.