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Figures
- Fig. 1
Isomap algorithm capacity. (Left) Isomap automatically finds the manifold of dimension 2 embedded in a Swiss roll (the manifold is an abstract mathematical space). (Right) Isomap creates a manifold of dimension 2 approximating the high-dimensional space of manually drawn digits (http://scikit-learn.org/).
- Fig. 2
Sample for each bundle of interest (cingulum, uncinate, arcuate) with the streamline representations obtained from tractography. Three alternative voxel-based representations are obtained for each bundle with different thresholds on the number of streamlines crossing the voxels. The threshold used in our study was considered optimal, preventing spurious voxels including few streamlines to be selected (see the uncinate representation for a low threshold) and preserving the topology of the bundle (see the split representation of arcuate branches for a high threshold). Note that from the low to the right threshold, the diameter of the bundle core decreases without qualitative changes in the shape.
- Fig. 3
First dimension of the left uncinate fasciculus Isomap. (Top) Moving average shapes (MAS) along the Isomap observed with 2 different orientations (for each orientation, the frontal horn of the bundle is on the left). The extreme MAS (green and magenta) are combined to highlight the shape feature encoded by the Isomap. This dimension captures the volume variability of the bundles. From the left to the right of the Isomap axis, the volume increases, while the bundle becomes more “fanned out” in the frontal lobe. More particularly, the ventrolateral orbitofrontal branch emerges toward the right of the axis. (Middle) Individual bundles are superimposed over the same MAS along the Isomap axis to show their distributions for both groups. (Bottom) Uncinate fasciculus sample and overall and centre-based boxplots of the localization in the isomap after adjustment for fractional anisotropy, age and sex.
- Fig. 4
Second dimension of the cingulum fasciculus Isomap. (Top) Moving average shapes (MAS) along the Isomap axis observed with 2 different orientations (for each orientation, the frontal horn of the bundle is on the left). The extreme MAS (green and magenta) are combined to highlight the shape feature encoded by the Isomap. This dimension captures a pure shape feature. From the left to the right of the Isomap axis, the volume of the frontal extremity increases while the volume of the parietal extremity decreases. (Middle) Distributions along the Isomap axis of the left bundles of patients with bipolar disorder versus controls superimposed over the same MAS. (Bottom) Cingulum sample and the corresponding uncinate fasciculus and overall and centre-based boxplots of the localization in the isomap after adjustment for fractional anisotropy, age and sex.
- Fig. 5
Second dimension of the arcuate fasciculus Isomap. (Top) Moving average shapes (MAS) along the Isomap axis observed with 2 different orientations (for each orientation, the frontal horn of the bundle is on the left). The extreme MAS (green and magenta) are combined to highlight the shape feature encoded by the Isomap. This dimension captures a pure shape feature: the extent of the development of the bundle toward the temporal pole. (Middle) Distributions along the Isomap axis of the left bundles of patients with bipolar disorder versus controls superimposed over the same MAS. (Bottom) Arcuate fasciculus sample and overall and centre-based boxplots of the localization in the Isomap after adjustment for fractional anisotropy, age and sex.
Tables
Characteristic Group; no. (%) or mean ± SD [range] BD, n = 118 Control, n = 86 Scan site Centre 1 24 (20.5) 22 (25.6) Centre 2 53 (45.3) 26 (30.2) Centre 3 40 (34.2) 38 (44.2) Male sex 47 (40.2) 41 (47.7) Age at MRI, yr 36.5 ± 10.4 [18–63] 37.3 ± 11.22 [19–66] Right-handedness 110 (96.5) 84 (97.7) IQ* 108.7 ± 10.58 107.39 ± 10.06 Medication Lithium 39 (33.3) — Anticonvulsants 64 (54.7) — Antipsychotic 52 (44.4) — Antidepressant 54 (46.2) — Age at onset, yr 20.8 ± 8.0 — YMRS score†‡§ 2.6 ± 3.7 — MADRS score†§ 3.5 ± 5.4 — HAMD-17 score‡ 9.9 ± 7.9 — BD = bipolar disorder; HAMD-17= Hamilton Rating Scale for Depression; NART = National Adult Reading Test; MADRS = Montgomery–Asberg Depression Rating Scale; SD = standard deviation; YMRS = Young Mania Rating Scale.
↵* Assessed using the NART.
↵† Recorded at centre 1.
↵‡ Recorded at centre 2.
↵§ Recorded at centre 3.
Bundle Df Dim Diagnosis FA Scanner Age Sex F1 p value F1 p value F2 p value F1 p value F1 p value Left AF 187 1 1.4 0.23 14.2 < 0.001* 2.1 0.13 5.1 0.026 0.8 0.78 2 15.1 < 0.001* 24.5 < 0.001* 1.9 0.16 3.5 0.06 0.3 0.61 Right AF 176 1 3.2 0.07 11.1 0.001† 0.6 0.54 7.8 0.006† 0.7 0.39 2 0.1 0.84 1.3 0.24 4.4 0.014 0 0.96 0.7 0.39 Left CG 187 1 0.4 0.54 48.6 < 0.001* 0.73 0.48 0 0.89 0.39 0.53 2 4.99 0.027† 0 0.87 2.5 0.08 0.8 0.37 0.3 0.56 Right CG 187 1 0. 0.91 32.4 < 0.001* 8.3 < 0.001† 0 0.99 0.8 0.91 2 3.5 0.06 1.5 0.22 10.7 < 0.001* 0.7 0.40 0 0.87 Left UN 187 1 4.4 0.036† 30.3 < 0.001* 26.1 < 0.001* 4.9 0.029† 2.8 0.10 2 1. 0.31 0.5 0.48 7.7 < 0.001† 3.0 0.08 1.7 0.20 Right UN 187 1 2. 0.16 3.0 0.08 39.7 < 0.001* 10.2 0.002† 0.3 0.57 2 2.9 0.09 2.8 0.09 36.1 < 0.001* 0 0.97 0.4 0.51 AF = arcuate fasciculus; CG = cingulum; Df = degrees of freedom; Dim = dimension; FA = fractional anisotropy; UN = uncinate fasciculus.
↵* Significant effect after Bonferroni correction for multiple tests (p < 4 × 10−4)
↵† Trend toward significance after Bonferroni correction for multiple tests (4 × 10−4 < p < 0.05).
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