Age-related changes in regional brain activation during phonological decoding and printed word recognition.

Using magnetic source imaging, age-related changes in spatiotemporal brain activation profiles associated with printed word recognition and phonological decoding (pseudoword reading) were examined in 27 adults and 22 children without reading problems. Adults showed a distinct spatiotemporal profile during reading of both types of print consisting of bilateral activation of occipital cortices, followed by strongly left-predominant activation of basal temporal regions, and, finally, left hemisphere temporoparietal (including the angular gyrus) and inferior frontal activation. Children lacked the clear temporal distinction in the engagement of basal and temporoparietal areas and displayed significantly weaker activation of the left inferior frontal gyrus. In addition, the consistent hemispheric asymmetries in the degree of activation of basal temporal regions that were present in the adult readers were not apparent in the children. In contrast, the strong left hemisphere preponderance in the degree of activation of temporoparietal areas was present in children as well as adults, regardless of the type of print they were asked to read. The data suggest that the degree of specialization of cortical regions for reading, as well as the pattern of regional interactions that supports this specialization, may change with age.