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 during semantic and phonological decision tasks using whole-brain echo-planar imaging. Nine right-handed healthy younger adults were compared to nine right-handed healthy older adult volunteers. While undergoing fMRI scanning, subjects completed three functional MRI auditory stimulation tasks requiring semantic or phonological decisions (match/mismatch) about word pairs (category-exemplar, category-function, pseudo-word). Performance scores on these tasks did not differ between age groups. The fMRI images were motion corrected, spatially normalized, and statistically analyzed for group similarities and differences using a random-effects model. For the semantic tasks, both older and younger adults showed activity within the inferior frontal gyms (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 were 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 atrophy index as a covariate. These findings highlight the similarities in semantic processing across age groups and suggest that global age related atrophy is not impacting activation significantly in healthy older adults.