Distinguishing the noise and attractor strength of coordinated limb movements using recurrence analysis

Abstract

The variability of coupled rhythmic limb movements is assumed to be a consequence of the strength of a movement's attractor dynamic and a constant stochastic noise process that continuously perturbs the movement system away from this dynamic. Recently, it has been suggested that the nonlinear technique of recurrence analysis can be used to index the effects of noise and attractor strength on movement variability. To test this, three experiments were conducted in which the attractor strength of bimanual wrist-pendulum movements (using coordination mode, movement frequency and detuning), as well as the magnitude of stochastic perturbations affecting the variability of these movements (using a temporally fluctuating visual metronome) was manipulated. The results of these experiments demonstrate that recurrence analysis can index parametric changes in the attractor strength of coupled rhythmic limb movements and the magnitude of metronome induced stochastic perturbations independently. The results of Experiments 1 and 2 also support the claim that differences between the variability of inphase and antiphase coordination, and between slow and fast movement frequencies are due to differences in attractor strength. In contrast to the standard assumption that the noise that characterizes interlimb coordination remains constant for different magnitudes of detuning (Delta omega) the results of Experiment 3 suggest that the magnitude of noise increases with increases in |Delta omega|.

A Dynamic Systems Approach to the Effects of Aging on Bimanual Coordination

“…Such an increase in asymmetry between the 2 hands could be (one of) the source(s) of the difference in pattern stability between young and older participants. Such a hypothesis is consistent with the results observed by Richardson et al [42] using cross-recurrence quantification analysis. They showed that modulations in frequency detuning between oscillatory hands influenced the magnitude of internal fluctuations and consequently relative phase variability.…”

“…They showed that modulations in frequency detuning between oscillatory hands influenced the magnitude of internal fluctuations and consequently relative phase variability. According to Richardson et al [42] , one could speculate that changes in frequency detuning resulted in rescaling of the magnitude of the perturbation process (i.e. noise) inherent to inter-limb coordination.…”

“…This result has already been observed in previous studies on bimanual coordination in young healthy adults [15,41] . According to the modeling of Haken et al [18] , it suggests that an increase in frequency neither changed the magnitude of noise present in the system nor the coupling strength [42] . These results are of importance for the existing knowledge in the domain of aging.…”

Movement synchronization fails during non-adaptive human-robot interaction

“…In line with [11,12], the relative phase difference between movement signals was calculated per trial and averaged for each start condition respectively. If in-phase synchronization occurred, a peak for data in the 0-20° region should be found, for anti-phase synchronization in the 160-180° region.…”

Auditory white noise reduces postural fluctuations even in the absence of vision

“…The data were down-sampled for these analyses to 50 Hz. RQA measures used were percent determinism, percent recurrence, and entropy (delay = 40, embedding dimension = 4, radius = 10), and the standard largest box size was used (Richardson et al 2007). Radial sway in low-and high-frequency ranges was examined separately to assess changes in slow and fast timescales of postural control (Yeh et al 2010(Yeh et al , 2014van den Heuvel et al 2009).…”