A developmental fMRI study of reading and repetition reveals changes in phonological and visual mechanisms over age

Abstract

In this study of reading development, children (ages 7-10) and adults (ages 18-32) performed overt single-word reading and aural repetition tasks on high-frequency word stimuli during functional magnetic resonance imaging. Most regions showed similar activity across age groups. These widespread regions of similarity indicate that children and adults use largely overlapping mechanisms when processing high-frequency words. Significant task-related differences included greater activity in occipital cortex for the read task, and greater activity in temporal cortex for the repeat task; activity levels in these regions were similar for adults and children. However, age group differences were found in several posterior regions, including a set of regions implicated in adult reading: the left supramarginal gyrus, the left angular gyrus, and bilateral anterior extrastriate cortex. The angular and supramarginal gyrus regions, hypothesized to play a role in phonology, showed decreased activity in adults relative to children for high-frequency words. The extrastriate regions had significant activity for both the visual read task and auditory repeat task in children, but just for the read task in adults, showing significant task and age interactions. These results are consistent with decreasing reliance on phonological processing, and increasing tuning of visual mechanisms, with age.

Figure 1.

Regions showing no significant differences between ages or tasks. An example region, location indicated by the arrow, is shown at right, with percent signal change on the y-axis, and time (in MR frames; each MR frame is 3.08 s) on the x-axis. Time courses are shown with standard error of the mean. Coordinates reported for this and all figures are in Talairach space. The orientation of all subsequent brain surfaces will follow the convention above. All surface-rendered images were created using CARET software and surface-based atlases (Van Essen 2002; Van Essen et al. 2001).

Figure 2.

Regions showing significant task-related (A) or age-related (B) effects. (A) Task-related regions: Pink indicates regions showing significant activity only for Read; Red indicates regions showing significantly more activity for Read than Repeat; Yellow indicates regions showing significantly more activity for Repeat than Read. An example region, location indicated by the arrow, is shown below the brain images with percent signal change on the y-axis, and time (in MR frames) on the x-axis. Time courses are shown with standard error of the mean. (B) Age-related regions: Light blue indicates regions showing significant activity only in children; Dark blue indicates regions showing significantly more activity in children than in adults. An example region, location indicated by the arrow, is shown below the brain images. All differences surpassed a Z-score of 2.5.

Figure 3.

Five bilateral extrastriate cortex regions showing both significant task-related and significant age-related effects. An example from each hemisphere, locations indicated by the arrows, are shown below the image with percent signal change on the y-axis, and time (in MR frames) on the x-axis. Time courses are shown with standard error of the mean. The left hemisphere exemplar region is within 8 mm of the purported vWFA.

Figure 4.

Two left hemisphere regions of interest. Region A, in the supramarginal gyrus, shows greater activity for children than adults. Region B, in the angular gyrus, shows significant activity only in children. Time courses are shown with standard error of the mean.