Similarities and differences in semantic and phonological processing with age: Patterns of functional MRI activation

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.