PT  - JOURNAL ARTICLE
AU  - P. Furmanek Mariusz
AU  - Madhur Mangalam
AU  - Damian G. Kelty-Stephen
AU  - Grzegorz Juras
TI  - Postural instability recruits shorter-timescale processes into the non-Gaussian cascade processes
AID  - 10.1101/2020.06.05.136895
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.06.05.136895
4099  - http://biorxiv.org/content/early/2020/06/07/2020.06.05.136895.short
4100  - http://biorxiv.org/content/early/2020/06/07/2020.06.05.136895.full
AB  - Healthy human postural sway exhibits strong intermittency, reflecting a richly interactive foundation of postural control. From a linear perspective, intermittent fluctuations might be interpreted as engagement and disengagement of complementary control processes at distinct timescales or from a nonlinear perspective, as cascade-like interactions across many timescales at once. The diverse control processes entailed by cascade-like multiplicative dynamics suggest specific non-Gaussian distributional properties at different timescales. Multiscale probability density function (PDF) analysis showed that when standing quietly, stable sand-filled loading of the upper extremities would elicit non-Gaussianity profiles showing a negative-quadratic crossover between short and long timescales. Unstable water-filled loading of the upper extremities would elicit simpler monotonic decreases in non-Gaussianity, that is, a positive-quadratic cancellation of the negative-quadratic crossover. Multiple known indices of postural sway governed the appearance or disappearance of the crossover. Finally, both loading conditions elicited Lévy-like distributions over progressively larger timescales. These results provide evidence that postural instability recruits shorter-timescale processes into the non-Gaussian cascade processes, that indices of postural sway moderate this recruitment, and that postural control under unstable loading shows stronger statistical hallmarks of cascade structure.Competing Interest StatementThe authors have declared no competing interest.