diff --git a/analysis/matlab/variations/unmerge_d0_13/learning_curve.png b/analysis/matlab/variations/unmerge_d0_13/learning_curve.png
index 9a1cd74..e35a036 100644
Binary files a/analysis/matlab/variations/unmerge_d0_13/learning_curve.png and b/analysis/matlab/variations/unmerge_d0_13/learning_curve.png differ
diff --git a/analysis/matlab/variations/unmerge_d0_13/learning_curve_rate.png b/analysis/matlab/variations/unmerge_d0_13/learning_curve_rate.png
index c77f4c3..ec6223c 100644
Binary files a/analysis/matlab/variations/unmerge_d0_13/learning_curve_rate.png and b/analysis/matlab/variations/unmerge_d0_13/learning_curve_rate.png differ
diff --git a/analysis/matlab/variations/unmerge_d0_13/plotcurve.m b/analysis/matlab/variations/unmerge_d0_13/plotcurve.m
index 8fb7f44..8399de2 100644
--- a/analysis/matlab/variations/unmerge_d0_13/plotcurve.m
+++ b/analysis/matlab/variations/unmerge_d0_13/plotcurve.m
@@ -38,9 +38,22 @@ legend([e1 e2], {sprintf('anodal, N = %d', na), sprintf('control, N = %d', nc)},
     'Location', 'northwest', 'Box', 'off');
 xlabel('training day'); ylabel(ylab);
 title(vname, 'Interpreter', 'none');
-set(gca, 'XTick', xd, 'XTickLabelRotation', 90, ...   % vertical x-axis tick labels
+% Vertical x-axis tick labels. XTickLabelRotation / xtickangle are NOT honored
+% by exportgraphics on a headless invisible figure, so draw the labels manually
+% as rotated text objects (which always render).
+set(gca, 'XTick', xd, 'XTickLabel', {}, 'Position', [0.13 0.20 0.80 0.70], ...
     'FontName', 'Arial', 'FontSize', 13, 'LineWidth', 1.5, 'Box', 'off');
-drawnow;                         % force layout so the rotation is applied headless
+drawnow;
+yl = ylim(gca);
+yb = yl(1) - 0.015 * (yl(2) - yl(1));
+for k = 1:numel(xd)
+    text(xd(k), yb, num2str(xd(k)), 'Parent', gca, 'Rotation', 90, ...
+        'HorizontalAlignment', 'right', 'VerticalAlignment', 'middle', ...
+        'FontName', 'Arial', 'FontSize', 13, 'Clipping', 'off');
+end
+xlh = get(gca, 'XLabel');            % push the axis label below the vertical ticks
+set(xlh, 'Units', 'normalized', 'Position', [0.5 -0.15 0]);
+drawnow;
 exportgraphics(fig, outFile, 'Resolution', 150);
 close(fig);
 fprintf('%s: wrote %s (anodal N=%d, control N=%d)\n', vname, outFile, na, nc);
diff --git a/analysis/matlab/variations/unmerge_d0_5/learning_curve.png b/analysis/matlab/variations/unmerge_d0_5/learning_curve.png
index 71777f7..fdb347c 100644
Binary files a/analysis/matlab/variations/unmerge_d0_5/learning_curve.png and b/analysis/matlab/variations/unmerge_d0_5/learning_curve.png differ
diff --git a/analysis/matlab/variations/unmerge_d0_5/learning_curve_rate.png b/analysis/matlab/variations/unmerge_d0_5/learning_curve_rate.png
index 23bcdaf..f86b755 100644
Binary files a/analysis/matlab/variations/unmerge_d0_5/learning_curve_rate.png and b/analysis/matlab/variations/unmerge_d0_5/learning_curve_rate.png differ
diff --git a/analysis/matlab/variations/unmerge_d0_5/plotcurve.m b/analysis/matlab/variations/unmerge_d0_5/plotcurve.m
index 8fb7f44..8399de2 100644
--- a/analysis/matlab/variations/unmerge_d0_5/plotcurve.m
+++ b/analysis/matlab/variations/unmerge_d0_5/plotcurve.m
@@ -38,9 +38,22 @@ legend([e1 e2], {sprintf('anodal, N = %d', na), sprintf('control, N = %d', nc)},
     'Location', 'northwest', 'Box', 'off');
 xlabel('training day'); ylabel(ylab);
 title(vname, 'Interpreter', 'none');
-set(gca, 'XTick', xd, 'XTickLabelRotation', 90, ...   % vertical x-axis tick labels
+% Vertical x-axis tick labels. XTickLabelRotation / xtickangle are NOT honored
+% by exportgraphics on a headless invisible figure, so draw the labels manually
+% as rotated text objects (which always render).
+set(gca, 'XTick', xd, 'XTickLabel', {}, 'Position', [0.13 0.20 0.80 0.70], ...
     'FontName', 'Arial', 'FontSize', 13, 'LineWidth', 1.5, 'Box', 'off');
-drawnow;                         % force layout so the rotation is applied headless
+drawnow;
+yl = ylim(gca);
+yb = yl(1) - 0.015 * (yl(2) - yl(1));
+for k = 1:numel(xd)
+    text(xd(k), yb, num2str(xd(k)), 'Parent', gca, 'Rotation', 90, ...
+        'HorizontalAlignment', 'right', 'VerticalAlignment', 'middle', ...
+        'FontName', 'Arial', 'FontSize', 13, 'Clipping', 'off');
+end
+xlh = get(gca, 'XLabel');            % push the axis label below the vertical ticks
+set(xlh, 'Units', 'normalized', 'Position', [0.5 -0.15 0]);
+drawnow;
 exportgraphics(fig, outFile, 'Resolution', 150);
 close(fig);
 fprintf('%s: wrote %s (anodal N=%d, control N=%d)\n', vname, outFile, na, nc);
diff --git a/analysis/matlab/variations/unmerge_d6_10/learning_curve.png b/analysis/matlab/variations/unmerge_d6_10/learning_curve.png
index 561cf02..7dcb7de 100644
Binary files a/analysis/matlab/variations/unmerge_d6_10/learning_curve.png and b/analysis/matlab/variations/unmerge_d6_10/learning_curve.png differ
diff --git a/analysis/matlab/variations/unmerge_d6_10/learning_curve_rate.png b/analysis/matlab/variations/unmerge_d6_10/learning_curve_rate.png
index d0df499..ffc52b7 100644
Binary files a/analysis/matlab/variations/unmerge_d6_10/learning_curve_rate.png and b/analysis/matlab/variations/unmerge_d6_10/learning_curve_rate.png differ
diff --git a/analysis/matlab/variations/unmerge_d6_10/plotcurve.m b/analysis/matlab/variations/unmerge_d6_10/plotcurve.m
index 8fb7f44..8399de2 100644
--- a/analysis/matlab/variations/unmerge_d6_10/plotcurve.m
+++ b/analysis/matlab/variations/unmerge_d6_10/plotcurve.m
@@ -38,9 +38,22 @@ legend([e1 e2], {sprintf('anodal, N = %d', na), sprintf('control, N = %d', nc)},
     'Location', 'northwest', 'Box', 'off');
 xlabel('training day'); ylabel(ylab);
 title(vname, 'Interpreter', 'none');
-set(gca, 'XTick', xd, 'XTickLabelRotation', 90, ...   % vertical x-axis tick labels
+% Vertical x-axis tick labels. XTickLabelRotation / xtickangle are NOT honored
+% by exportgraphics on a headless invisible figure, so draw the labels manually
+% as rotated text objects (which always render).
+set(gca, 'XTick', xd, 'XTickLabel', {}, 'Position', [0.13 0.20 0.80 0.70], ...
     'FontName', 'Arial', 'FontSize', 13, 'LineWidth', 1.5, 'Box', 'off');
-drawnow;                         % force layout so the rotation is applied headless
+drawnow;
+yl = ylim(gca);
+yb = yl(1) - 0.015 * (yl(2) - yl(1));
+for k = 1:numel(xd)
+    text(xd(k), yb, num2str(xd(k)), 'Parent', gca, 'Rotation', 90, ...
+        'HorizontalAlignment', 'right', 'VerticalAlignment', 'middle', ...
+        'FontName', 'Arial', 'FontSize', 13, 'Clipping', 'off');
+end
+xlh = get(gca, 'XLabel');            % push the axis label below the vertical ticks
+set(xlh, 'Units', 'normalized', 'Position', [0.5 -0.15 0]);
+drawnow;
 exportgraphics(fig, outFile, 'Resolution', 150);
 close(fig);
 fprintf('%s: wrote %s (anodal N=%d, control N=%d)\n', vname, outFile, na, nc);
diff --git a/analysis/matlab/variations/unmerge_d6_13/learning_curve.png b/analysis/matlab/variations/unmerge_d6_13/learning_curve.png
index 310be29..3405af8 100644
Binary files a/analysis/matlab/variations/unmerge_d6_13/learning_curve.png and b/analysis/matlab/variations/unmerge_d6_13/learning_curve.png differ
diff --git a/analysis/matlab/variations/unmerge_d6_13/learning_curve_rate.png b/analysis/matlab/variations/unmerge_d6_13/learning_curve_rate.png
index 558ce66..482bb0c 100644
Binary files a/analysis/matlab/variations/unmerge_d6_13/learning_curve_rate.png and b/analysis/matlab/variations/unmerge_d6_13/learning_curve_rate.png differ
diff --git a/analysis/matlab/variations/unmerge_d6_13/plotcurve.m b/analysis/matlab/variations/unmerge_d6_13/plotcurve.m
index 8fb7f44..8399de2 100644
--- a/analysis/matlab/variations/unmerge_d6_13/plotcurve.m
+++ b/analysis/matlab/variations/unmerge_d6_13/plotcurve.m
@@ -38,9 +38,22 @@ legend([e1 e2], {sprintf('anodal, N = %d', na), sprintf('control, N = %d', nc)},
     'Location', 'northwest', 'Box', 'off');
 xlabel('training day'); ylabel(ylab);
 title(vname, 'Interpreter', 'none');
-set(gca, 'XTick', xd, 'XTickLabelRotation', 90, ...   % vertical x-axis tick labels
+% Vertical x-axis tick labels. XTickLabelRotation / xtickangle are NOT honored
+% by exportgraphics on a headless invisible figure, so draw the labels manually
+% as rotated text objects (which always render).
+set(gca, 'XTick', xd, 'XTickLabel', {}, 'Position', [0.13 0.20 0.80 0.70], ...
     'FontName', 'Arial', 'FontSize', 13, 'LineWidth', 1.5, 'Box', 'off');
-drawnow;                         % force layout so the rotation is applied headless
+drawnow;
+yl = ylim(gca);
+yb = yl(1) - 0.015 * (yl(2) - yl(1));
+for k = 1:numel(xd)
+    text(xd(k), yb, num2str(xd(k)), 'Parent', gca, 'Rotation', 90, ...
+        'HorizontalAlignment', 'right', 'VerticalAlignment', 'middle', ...
+        'FontName', 'Arial', 'FontSize', 13, 'Clipping', 'off');
+end
+xlh = get(gca, 'XLabel');            % push the axis label below the vertical ticks
+set(xlh, 'Units', 'normalized', 'Position', [0.5 -0.15 0]);
+drawnow;
 exportgraphics(fig, outFile, 'Resolution', 150);
 close(fig);
 fprintf('%s: wrote %s (anodal N=%d, control N=%d)\n', vname, outFile, na, nc);