Entrainment to a real time fractal visual stimulus modulates fractal gait dynamics

Abstract

Fractal patterns characterize healthy biological systems and are considered to reflect the ability of the system to adapt to varying environmental conditions. Previous research has shown that fractal patterns in gait are altered following natural aging or disease, and this has potential negative consequences for gait adaptability that can lead to increased risk of injury. However, the flexibility of a healthy neurological system to exhibit different fractal patterns in gait has yet to be explored, and this is a necessary step toward understanding human locomotor control. Fifteen participants walked for 15min on a treadmill, either in the absence of a visual stimulus or while they attempted to couple the timing of their gait with a visual metronome that exhibited a persistent fractal pattern (contained long-range correlations) or a random pattern (contained no long-range correlations). The stride-to-stride intervals of the participants were recorded via analog foot pressure switches and submitted to detrended fluctuation analysis (DFA) to determine if the fractal patterns during the visual metronome conditions differed from the baseline (no metronome) condition. DFA α in the baseline condition was 0.77±0.09. The fractal patterns in the stride-to-stride intervals were significantly altered when walking to the fractal metronome (DFA α=0.87±0.06) and to the random metronome (DFA α=0.61±0.10) (both p<.05 when compared to the baseline condition), indicating that a global change in gait dynamics was observed. A variety of strategies were identified at the local level with a cross-correlation analysis, indicating that local behavior did not account for the consistent global changes. Collectively, the results show that a gait dynamics can be shifted in a prescribed manner using a visual stimulus and the shift appears to be a global phenomenon.

Influence of Internal and External Noise on Spontaneous Visuomotor Synchronization

“…Accordingly, optimal structures of frequency variability in participants and/or stimulus movements might also facilitate spontaneous visuomotor synchronization. Future research may well benefit from controlling the variability structure in participants' movement and employing both correlated and uncorrelated noise structures for stimulus movements (Hunt, McGrath, & Stergiou, 2014;Rhea, Kiefer, D'Andrea, Warren, & Aaron, 2014;Torre, Varlet, & Marmelat, 2013). The facilitating effects of external stimulus noise may be strengthened with more correlated structures.…”

Fractal Gait Patterns Are Retained after Entrainment to a Fractal Stimulus

“…In the next 15 minutes (synchronization phase), the participants synchronized their gait cycle to a visual metronome that exhibited persistence (DFA α = 0.98). As in our previous work [27], the visual metronome consisted of a red flashing square that was projected in front of the treadmill and participants were asked to synchronize to the metronome by being at right heel contact when the red square flashed. The average interval between red square flashes was 1.00±0.07 sec.…”

“…This experiment was designed to replicate and expand our previous work using a visual stimulus exhibiting fractal timing patterns as a mechanism for individuals to develop a desired change in fractal timing patterns of gait [27]. This was accomplished by instructing the participants to entrain their gait cycle to the visual stimulus.…”

“…Specifically, the development of new interventions to change gait variability patterns would be a unique way to potentially restore functional gait behavior [26]. Our previous work has shown that fractal patterns in gait can be altered when participants synchronize their stride-to-stride intervals to a visual metronome (flashing square on a screen) while they walk on a treadmill [27]. The intervals between flashes of the visual metronome were not consistent; rather, they exhibited a variety of fractal patterns.…”

Retracted: Mathematical‐based modeling and prediction of the effect of external stimuli on human gait

“…They indicated that the auditory stimuli have the strongest influence on human gait compared to other types of stimuli [4]. See also [5]. In another work Kaipust et al investigated the effects of different auditory stimuli on two groups of subjects, young and elderly adults.…”