Fig 1.
Typical images/maps obtained with this MRI protocol.
Anatomical T2 weighted (T2W) image; shear modulus (G*) map, as measured by MRE at 800 Hz; fractional anisotropy (FA), mean diffusivity (MD), axial and radial diffusivity (AD and RD) maps, as measured with DTI (Bregma -0.72 mm (29)). Anatomical images were used to measure the cross-sectional areas of the ventricular system (green), whole-brain (white), and deep gray matter (red), along with the cortical thickness in the middle slice acquired (navy blue). The cortical thickness was averaged over 5 locations on the “roof” of the lateral ventricles. The magnitude of the complex shear modulus (G*) was calculated for the cortex (navy blue) and deep gray matter (red). FA, MD, RD and AD were obtained for the corpus callosum (yellow), external (pink) and internal (purple) capsules.
Fig 2.
Typical histological sections of a poly (I:C) rat brain stained with luxol fast blue and cresyl violet (top row) and with Iba-1 (red), NeuN (green) and DAPI (blue) (bottom row) at 10 weeks after birth. Regions of interest are shown on the histological sections.
Fig 3.
Cross-sectional areas of the ventricles (A), whole-brain (B), deep gray matter (C), and cortical thickness (D) measured in controls (n = 8, ●) and poly (I:C) rats (n = 12, ○) at week 4 and week 10 after birth (mean ± standard deviation). Data were analyzed with a repeated two-way ANOVA with Sidak’s multiple comparisons.
Fig 4.
Corpus callosum MR diffusion properties (mean ± standard deviation) in controls (●) and poly (I:C) rats (○) measured at 4 and 10 weeks after birth.
(A) Fractional anisotropy—FA, (B) Mean diffusivity–MD, (C) Axial diffusivity–AD, and (D) Radial diffusivity–RD. MD, RD and AD increased with age in poly (I:C) rats, while only AD increased from week 4 to week 10 in controls. FA of the corpus callosum did not differ between groups and did not change with age. Data were analyzed with a mixed-effects model with Sidak’s multiple comparisons.
Fig 5.
Internal capsule MR diffusion properties (mean ± standard deviation) in controls (●) and poly (I:C) rats (○) measured at 4 and 10 weeks after birth.
(A) Fractional anisotropy—FA, (B) Mean diffusivity–MD, (C) Axial diffusivity–AD, and (D) Radial diffusivity—RD. MD and AD increased with age only in poly (I:C) rats. RD was lower in poly (I:C) rats at week 4. Data were analyzed with a mixed-effects model with Sidak’s multiple comparisons.
Fig 6.
External capsule MR diffusion properties (mean ± standard deviation) in controls (●) and poly (I:C) rats (○) measured at 4 and 10 weeks after birth.
(A) Fractional anisotropy—FA, (B): Mean diffusivity–MD, (C) Axial diffusivity–AD, and (D) Radial diffusivity–RD. Increases in all four MR diffusion parameters with age was only seen in poly (I:C) rats. Data were analyzed with a mixed-effects model with Sidak’s multiple comparisons.
Fig 7.
Shear modulus (G*)(mean ± standard deviation) of the cortex (A) and deep gray matter (B), measured at 800Hz in controls (●) and poly (I:C) rats (○) at weeks 4 and 10 after birth. Cortical G* increased from week 4 to week 10 only in control rats. Data were analyzed with a mixed-effects model with Sidak’s multiple comparisons. P values for significant Sidak’s comparisons are reported.
Table 1.
Histological measurements.
Fig 8.
Estimates of the Pearson correlations with ventricle cross-sectional area and their 95% confidence intervals (CI).
Radial diffusivity (RD) in the internal capsule at week 4 (A) and fractional anisotropy (FA) in the external capsule at week 4 (B); cell density at week 10 in the corpus callosum (C) and myelin density at week 10 in the internal capsule (D) across the whole sample. Control (●) and poly (I:C) rats (○) are indicated. Bonferroni-adjusted confidence intervals are reported in the S1 Table.
Table 2.
Estimates of the correlations with ventricle size.