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. 2026 Apr 1;20:1702124. doi: 10.3389/fnins.2026.1702124

Figure 5.

Four scatter plots labeled A through D show log-transformed gamma shape versus scale for NSR across tasks: resting, drawing, pointing, and peg, with red points for control and blue for pain participants. Insets display probability density functions for MMS inter-burst intervals by group. Panel E presents a heatmap comparing pairwise IBI Gamma NSR Ranksum tests across all groups and tasks, with color indicating similarity. Panels F, G, and H show scatter plots of delta gamma values (ΔΓNSR vs ΔΓSK) for drawing, pointing, and peg tasks, respectively, with group differentiation by color.

The continuous gamma family of probability distributions fits the empirical IBI data well in a maximum likelihood estimation sense, with 95% confidence. (A) Control and pain conditions at rest, (B) Drawing, (C) Pointing, and (D) Peg tasks. Each (Гshape, Гscale) point on the gamma parameter plane is plotted to reveal a self-emerging pattern; the log–log scatter aligns according to a tight linear negative correlation: as the distribution becomes more symmetric (with increasing shape values), scale (dispersion) values decrease. The scale is the noise-to-signal ratio (NSR, variance over the mean). (E) The pairwise comparison of the NSR according to the rank-sum test reveals statistically significant differences (p < 0.01) for all tasks during the pain state, relative to the absolute difference between pain and control states for the resting task. (F–H) The parameter plane represents the difference in NSR vs. the difference in skewness for each task relative to the resting task, in both the control (red) and pain (blue) blocks.