Article Figures & Data
Figures
- Figure 1.
A, Lesion distribution volume. The color code indicates in how many individuals of our patient sample (n = 20) a given voxel was lesioned, in absolute numbers (ranging from 1 to 6). In our sample, a maximum of six of the patients had a same voxel lesioned. B, Lesion-symptom map. Green, Voxels that, when lesioned, are associated with a significantly higher accuracy cost during contralesional minus ipsilesional orienting trials when stimuli are presented bilaterally and symmetrically than with unilateral double stimulation (LESS index). Statistical test: Student's t test (corrected p < 0.05). C, Same analysis as in B except for the use of a Brunner-Munzel instead of a Student's t test (corrected p < 0.05). D, Lesion-symptom map. Red, Voxels that, when lesioned, are associated with a significant accuracy cost during contralesional versus ipsilesional orienting under bilateral symmetrical stimulation conditions. Student's t test (corrected p < 0.05). L, Left; R, right.
- Figure 2.
Experimental paradigm applied in patients and during fMRI in healthy volunteers. A central instructive cue (200 ms) pointed to one of the four quadrants. After a 200 ms delay, a relevant grating was presented in the cued quadrant together with an irrelevant grating. Subjects were instructed to fixate a central fixation point and press a left-hand or right-hand key depending on the orientation of the target grating. A–C, The distracter could be either in the quadrant symmetrical to that occupied by the target (A), in the other quadrant of the same hemifield (B), or in the diagonally opposite quadrant (C). In this example, distracter and target have different orientations, but in reality, the orientation could be either the same or different.
- Figure 3.
Regression plot. x-axis, LESS index; y-axis, lesion size (in cubic centimeters).
- Figure 4.
A, Main fMRI experiment. Brain activity map for the contrast of bilateral symmetrical stimulation minus unilateral vertical stimulation. Thresholded at uncorrected p < 0.001. B, C, Main fMRI experiment. Time-activity curves in the left (B) and right (C) IPS cluster, respectively, shown in A. Percentage of BOLD signal change averaged over all 23 healthy participants and all 3 × 3 × 3 mm3 voxels within the left (total number of voxels, 62) or right (total number of voxels, 22) IPS cluster, respectively. x-axis, Time in seconds. Dark blue, Left-sided attention, bilateral symmetrical stimulation; red, right-sided attention, bilateral symmetrical stimulation; cyan, left-sided attention, unilateral double stimulation along a vertical axis; black, right-sided attention, unilateral double stimulation. D, E, Effect of axis of configuration across hemifields. Green, Left-sided attention, bilateral diagonal stimulation; magenta, right-sided attention, bilateral diagonal stimulation. D, Percentage of BOLD signal change averaged over all 18 participants and all 62 voxels of the left IPS cluster shown in A. E, Percentage of BOLD signal change averaged over all 18 participants and all voxels of the right IPS area of overlap shown in yellow in Figure 6. Had we averaged all 22 voxels of the right IPS cluster shown in A, the profile would have been practically identical to that of the area of overlap. F, G, Sensory control experiment. F, Percentage of BOLD signal change averaged over all 12 participants and all 62 voxels of the left IPS cluster shown in A. G, Percentage of BOLD signal change averaged over all 12 participants and all voxels of the right IPS area of overlap shown in yellow in Figure 6. L, Left; R, right.
- Figure 5.
Main experiment. Time activity curve of the left occipitotemporal cluster of activity obtained by contrasting bilateral symmetrical stimulation minus unilateral double stimulation. Percentage of BOLD signal change was averaged for all 23 participants and all 34 voxels belonging to this cluster. The color code is identical to that used in Figure 4.
- Figure 6.
Overlap (yellow) between lesion-symptom map (green; Fig. 1B) and fMRI activity map (red; Fig. 4A). Projection on the cortical surface using CARET (http://brainmap.wustl.edu). A set of selected activity and rTMS peaks from the literature has also been added (Sereno et al., 2001; Woldorff et al., 2004; Hung et al., 2005; Kincade et al., 2005; Summerfield et al., 2006; Cicek et al., 2007; Molenberghs et al., 2007: Ruff et al., 2008). RH, Right hemisphere.
- Figure 7.
Lesion visualization in each of the four patients who had a pathological LESS index. The lesion is shown in white. Case numbers correspond to those in Table 1.
- Figure 8.
fMRI experiments in healthy volunteers. Left-sided and right-sided attention trials have been pooled. A, B, Orientation control experiment. A, Stimulus display. B, Time activity curve in the right IPS volume of overlap (Fig. 6, yellow), averaged over all four participants. C, D, Replication of the results from the main experiment in elderly controls. C, Stimulus display. D, Time activity curve in the right IPS volume of overlap, averaged over all eight participants E, F, Effect of display symmetry. E, Stimulus display. F, Time-activity curves, averaged over all 11 participants and all voxels belonging to the right IPS volume of overlap. G, H, Effect of axis of configuration within hemifields. G, Stimulus display. H, Time-activity curves. y-axis, Percentage BOLD signal increase, averaged over all eight participants and all voxels belonging to the right IPS volume of overlap.
Tables
Case Age Sex Lesion Lesion size (mm3) Time Extinction L/B/R Bells L/M/R Bisection (%) DS Hand used Contralesional orienting Ipsilesional orienting LESS B symm (%) U vert (%) B symm (%) U vert (%) 20 80 M R 64617 18 weeks 10/5/10 3/1/0 +6.3 5 R 64 94 94 97 −27 17 62 M R 89666 4 d 10/3/10 2/0/0 +5.3 5 R 47 58 58 42 −27 11 54 M R 30248 5 d 10/8/10 2/0/0 +6.6 5 R 65 76 98 85 −24 10 42 M R 43448 6 d 4/3/10 4/3/1 +18.7 7 R 46 60 79 70 −23 5 61 M L 18452 7 d 10/10/10 0/0/1 −5.2 7 L 89 97 94 92 −10 16 35 M L 64443 9 weeks 10/10/10 0/0/0 −1.0 4 R 97 100 100 94 −9 12 79 F R 40756 2 weeks 10/10/10 2/1/1 −3.8 5 R 86 91 97 97 −5 3 68 F R 10998 22 weeks 10/10/10 0/0/0 −3.0 7 R 89 97 97 100 −5 19 44 M R 161207 13 weeks 10/10/10 0/0/0 +5.0 6 R 86 94 97 100 −5 1 60 M R 29618 24 weeks 10/10/10 1/1/0 −1.8 7 R 97 100 100 100 −3 4 64 M R 107228 28 weeks 10/10/10 3/0/1 +4.1 5 R 58 64 64 67 −3 15 62 F L 17006 19 weeks 10/10/10 0/0/0 −0.4 6 R 92 89 92 86 −3 14 66 M L 95094 18 weeks 10/10/10 1/1/2 −0.5 7 R 100 96 100 96 0 2 55 M R 2568 20 weeks 10/10/10 1/0/0 −3.6 5 L 93 92 86 86 1 7 37 M L 11209 3 weeks 10/10/10 0/0/0 −0.4 5 R 100 95 100 97 2 9 37 F R 8480 2 weeks 10/10/10 2/0/1 +0.9 9 R 76 76 78 80 2 18 61 F L 1025 31 weeks 10/10/10 0/0/0 −2.0 6 R 94 89 94 94 5 8 76 M L 3966 5 d 10/10/10 1/1/2 −4.6 4 R 92 97 83 97 9 13 65 M R 49459 2 weeks 10/10/10 1/1/1 +4.0 6 R 97 92 92 97 10 6 52 M R 14307 21 weeks 10/10/10 2/1/0 −5.9 5 R 83 72 94 97 14 -
Cases were numbered consecutively but are ranked in this table in increasing order of LESS index. Bold values indicate significant difference between individual's score on the experimental task and control group [modified ttest, statistical threshold two-tailed p< 0.05 (Crawford and Garthwaite, 2005)]. Bold and underlined values indicate statistical threshold two-tailed p< 0.005 (Crawford and Garthwaite, 2005). LESS, Difference in accuracy based on the contrast [contralesional orienting, symmetrical stimulation minus ipsilesional orienting, symmetrical stimulation] − [contralesional orienting, contralesional stimulation minus ipsilesional orienting, ipsilesional stimulation]; L, left; R, right; B, bilateral; M, middle; Bells, number of omissions on the Bells test; Bisection, positive values are deviations to the patient's right side; Hand used, hand used in the experimental task; DS, digit span forward; B symm, bilateral symmetrical; U vert, unilateral vertical.
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Bilateral symmetrical Unilateral vertical Bilateral diagonal Unilateral single First psychophysical experiment RT (ms) 845 (160) 819 (160) 818 (146) 789 (161) Percentage correct (%) 78.8 (7.8) 81.7 (7.7) 82.0 (9.4) 82.9 (9.0) Mean number of saccades per run 0.78 (0.39) 0.79 (0.43) 0.70 (0.60) 0.90 (0.47) Second psychophysical experiment RT (ms) 735 (174) 692 (168) 700 (162) 655 (151) Percentage correct (%) 87.4 (10.4) 88.5 (11.1) 88.3 (9.3) 90.8 (7.8) Mean number of saccades per run 0.88 (0.67) 0.89 (0.78) 0.87 (0.83) 0.97 (0.79) -
Values are mean and SD.
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Bilateral symmetrical Unilateral double Single Bilateral diagonal Main experiment Reaction times (ms) 797 (146) 780 (142) 786 (147) % Correct 91.5 (7.5) 91.6 (7.6) 89.4 (10.2) Saccades per run 0.66 (0.42) 0.72 (0.31) 0.56 (0.54) Effect of configuration axis across hemifields Reaction times (ms) 857 (179) 847 (172) 845 (170) % Correct 71.6 (9.9) 70.9 (10.3) 71.8 (8.8) Saccades per run 0.60 (0.32) 0.67 (0.49) 0.54 (0.29) Case Time (weeks) Contra Ipsi Inter (LESS) Contra Ipsi Inter Contra Ipsi Inter B symm (%) U vert (%) B symm (%) U vert (%) B asymm (%) Corr vert (%) B asymm (%) Corr vert (%) Hor unilat (%) Vert unilat (%) Hor unilat (%) Vert unilat (%) 20 68 58 67 78 69 −18 56 78 75 69 −28 53 78 75 75 −25 17 64 58 69 67 64 −14 56 69 64 61 −16 56 66 63 63 −10 10 164 89 89 89 83 −6 97 94 92 97 2 81 78 78 81 0 -
The interaction refers to the difference between contralesional (Contra) and ipsilesional (Ipsi) orienting with horizontally configured stimuli versus vertically configured stimuli. B, Bilateral; symm, symmetrical; asymm, asymmetrical; Hor, horizontal; Vert, vertical; U unilateral; corr, corresponding; Inter, interaction. Bold indicates significant difference from 10 age-matched healthy controls at two-tailed p< 0.05 (Crawford and Garthwaite, 2005); underlined, significantly different from controls at two-tailed p< 0.005.
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