Sc. Johnson et al., Similarities and differences in semantic and phonological processing with age: Patterns of functional MRI activation, AGING NEURO, 8(4), 2001, pp. 307-320
In this investigation, we analyzed the effect of age on fMRI activation dur
ing semantic and phonological decision tasks using whole-brain echo-planar
imaging. Nine right-handed healthy younger adults were compared to nine rig
ht-handed healthy older adult volunteers. While undergoing fMRI scanning, s
ubjects completed three functional MRI auditory stimulation tasks requiring
semantic or phonological decisions (match/mismatch) about word pairs (cate
gory -exemplar, category -function, pseudo-word). Performance scores on the
se tasks did not differ between age groups. The fMRI images were motion cor
rected, spatially normalized, and statistically analyzed for group similari
ties and differences using a random-effects model. For the semantic tasks,
both older and younger adults showed activity within the inferior frontal g
yrus (left more than right) and left superior temporal gyrus, whereas small
regional age differences (younger > older) were found in the left inferior
precentral region. For the phonologic task, common areas of activation wer
e found in the superior temporal gyrus (left more than right). Age-related
differences in the phonologic task were observed predominantly in the right
angular region. The results were not changed by entry of a quantitative at
rophy index as a covariate. These findings highlight the similarities in se
mantic processing across age groups and suggest that global age related atr
ophy is not impacting activation significantly in healthy older adults.