Article Figures & Data
Figures
- Figure 1.
Whole-brain matter volume differences in dyslexics when compared with either age-matched or reading level-matched controls. A, GMV differences. Whole-brain renderings for the GMV comparisons between dyslexics with both age-matched and reading level-matched groups at a height threshold of p < 0.01 uncorrected, and a cluster level threshold of p < 0.01 FWE corrected. Age-matched controls showed greater GMV than dyslexics in left middle temporal gyrus, left anterior cingulate gyrus, right precentral gyrus, right middle frontal gyrus, and right anterior superior temporal gyrus. No significant results were found for the dyslexics > controls contrast when matched on age. Reading level-matched controls showed greater GMV than dyslexics in right precentral gyrus. Dyslexics showed greater GMV than the reading level-matched controls in left middle temporal gyrus. See Table 2 for details on all clusters. B, WMV differences. The same whole-brain renderings as in A, but this time for WMV comparisons of dyslexics and the two control groups. Age-matched controls showed greater WMV than dyslexics in left paracentral lobule, left middle frontal and superior frontal gyrus, right middle frontal gyrus, right precentral gyrus, right WM anterior to the thalamus, and right subgyral temporal WM. No significant results were found for the dyslexics > controls contrast when matched on age. Also, no significant results were found for the controls > dyslexics contrast for the reading level-matched comparison. Dyslexics showed greater WMV than reading level-matched controls in right WM just lateral to the putamen. See Table 3 for details on all clusters.
- Figure 2.
Gray and white matter intensities in ROIs. A, Average GMV intensity within ROIs (identified in the whole-brain, age-matched controls > dyslexics GMV comparison). For the dyslexic versus control comparisons in groups matched on age, all ROIs were, as expected, significantly different. However, when comparing the same dyslexics with a younger control group matched on reading level, most areas failed to show a difference. To probe for a possible role for age-related changes in the typical readers, the right chart shows between-group differences in GMV in the younger versus older control group in these same ROIs. B, Average WMV intensity within ROIs (identified in the whole-brain, age-matched controls > dyslexics WMV comparison). As above, all ROIs were significant in the comparisons of dyslexics and controls matched on age, as expected. There were no significant differences in these ROIs when comparing the dyslexics with controls matched on reading level. Again, the right chart gauges differences that exist between younger and older typical readers, this time in WMV. Like above, there was a trend for age-related differences in these regions, with left middle frontal gyrus and superior frontal gyrus being statistically significant. *p < 0.05 Bonferroni corrected for multiple comparisons. #p = 0.05 Bonferroni corrected for multiple comparisons.
Tables
Dyslexics Control AGE Control READ p values: dyslexics versus control AGE p values: dyslexics versus control READ N 15 15 15 Age 9.8 years (SD, 1.5 years) 9.9 years (SD, 2.7 years) 7.4 years (SD, 0.9 year) 0.8374 3.49 × 10−5 Gender 6 boys, 9 girls 9 boys, 6 girls 8 boys, 7 girls 0.2893 0.4814 Performance IQ: standard score 101.3 (SD, 12.3) 102.3 (SD, 8.2) 109.2 (SD, 14.0) 0.7960 0.1137 Word identification: standard score 77.4 (SD, 7.6) 118.2 (SD, 8.3) 3.48 × 10−14 Word identification: reading age 7.6 (SD, 0.9) 8.1 (SD, 0.5) 0.0621 Passage comprehension: standard score 78.3 (SD, 11.0) 110.3 (SD, 10.0) 3.54 × 10−8 Passage comprehension: reading age 7.3 (SD, 1.0) 7.6 (SD, 0.6) 0.3400 Hemisphere Talairach coordinates (X, Y, Z) Cluster size Z score Cluster p value Peak anatomical location Age-matched comparison Controls > dyslexics Lefta −45, −15, −12 1289 3.79 4.37 × 10−7 Middle temporal gyrus, BA 21 Left −16, −18, 40 1026 3.17 7.79 × 10−6 Cingulate gyrus, BA 24 Righta 42, −10, 33 1545 5.33 3.18 × 10−8 Precentral gyrus, BA 6 Right 34, 38, 12 711 4.66 3.49 × 10−4 Middle frontal gyrus, BA 10 Right 51, 9, −13 518 3.29 0.005 Superior temporal gyrus, BA 38 Dyslexics > controls No significant results Reading level-matched comparison Controls > dyslexics Right 42, −13, 32 694 3.72 0.001 Precentral gyrus, BA 6 Dyslexics > controls Left −63, −53, 1 672 5.04 0.001 Middle temporal gyrus, BA 21 ↵aClusters that survive both FWE and nonstationary cluster corrections.
Hemisphere Talairach coordinates (X, Y, Z) Cluster size Z score Cluster p value Peak anatomical location Age-matched comparison Controls > dyslexics Left −4, −24, 52 784 4.53 4.78 × 10−6 Paracentral lobule Left −39, 43, 13 1051 4.05 9.94 × 10−8 Middle frontal gyrus Left −30, −13, 45 918 3.49 6.53 × 10−7 Middle frontal gyrus Left −20, 44, 32 356 3.54 0.007 Superior frontal gyrus Right 48, 26, 24 1063 4.47 8.42 × 10−8 Middle frontal gyrus Righta 42, −8, 36 3465 4.30 3.54 × 10−19 Precentral gyrus Right 40, −42, −5 878 3.52 1.17 × 10−6 Subgyral temporal lobe Right 10, −3, 17 1021 3.38 1.51 × 10−7 Anterior to thalamus Dyslexics > controls No significant results Reading level-matched comparison Controls > dyslexics No significant results Dyslexics > controls Right 27, −4, −9 386 3.80 0.004 Lateral to putamen ↵aClusters that survive both FWE and nonstationary cluster corrections.
