Orderliness of Visual Stimulus Motion Mediates Sensorimotor Coordination

We explored the coupling of gaze and postural sway to the motion of a visual stimulus, to further understand sensorimotor coordination. Visual stimuli consisted of a horizontally oscillating red dot, moving with periodic (sine), chaotic, or aperiodic (brown noise) temporal structure. Cross Recurrence Quantification Analysis (cRQA) was used to investigate the coupling between each measured signal with the time series of the visual stimulus position. The cRQA parameter of percent determinism indicated similar strength of coupling of gaze with either periodic or chaotic motion structures, yet weaker coupling to aperiodic stimulus motion. The cRQA parameter of Maxline indicated a particular affinity toward chaotic motion. Analysis of postural coupling supports the idea that the complex periodicity of body sway affords interactivity with non-simple environmental dynamics. These results collectively strengthen the argument that chaos is an invariant and beneficial feature of biological motion, a feature which may be critical for immediate and robust coordination of the self with the environment and other environmental agents

Gaze and posture coordinate differently with the complexity of visual stimulus motion

In this study, we explored whether gaze and posture would exhibit coordination with the motion of a presented visual stimulus, specifically with regard to the complexity of the motion structure. Fourteen healthy adults viewed a set of four visual stimulus motion conditions, in both self-selected and semi-tandem stance, during which the stimulus moved horizontally across a screen, with position updated to follow a sine, chaos, surrogate, or random noise trajectory. Posture was measured using a standard force platform in self-selected and semi-tandem stance conditions while gaze was recorded using image-based eye-tracking equipment. Cross-correlation confirmed the continuous coordination of gaze with each type of stimulus motion, with increasing lag as stimulus motion complexity increased. Correlation dimension and approximate entropy were used to assess the complexity of the measured gaze and posture behaviors, with these values compared against those of the actual stimulus via ANOVA and dependent t tests. We found that gaze behavior was particularly sensitive to the complexity of the stimulus motion, according to both metrics. Posture seemed to be unaffected by stimulus motion viewing; however, different stance conditions did exhibit differences in posture metrics. Our results support an evolving understanding of how vision is used for determining perception and action

Asynchrony between subtalar and knee joint function during running

Purpose: It has been suggested that during running proper coordination between subtalar joint pronation/supination and knee joint flexion/extension via tibial rotation is important to attenuate ground reaction impact forces (GRIF). Lack of coordination may produce over time a wide range of injuries. The goal of this study was to investigate the relationship between subtalar pronation/supination and knee flexion/extension with GRIF increases during distance running. Methods: Eight subjects ran under different speeds (a self-selected pace, 10% faster, 10% slower, and 20% faster) and over different obstacle heights (5%, 10%, and 15% of their standing height) on their self-selected pace. Sagittal, rear-view kinematic, and GRIF data were collected. The biomechanical results were also compared with data from a clinical evaluation of the subjects. Results: Speed changes and obstacle heights produced increases in GRIF and differences between rearfoot and knee angular velocities. The higher the obstacle and the faster the speed, the greater the GRIF and the greater the velocity differences. A change of the rearfoot angle curve from a unimodal (one minimum) to a bimodal (two minimums) parabolic configuration was also observed. The appearance of the second minimum was attributed to a lateral deviation of the tibia as a rebound effect due to the increased impact with the ground. The velocity differences between the actions of the subtalar and the knee joint, which in essence capture the antagonistic nature of their relationship, produced the highest correlation with the clinical evaluation. Conclusions: It was suggested that a possible mechanism responsible for various running injuries could be lack of coordination between subtalar and knee joint actions. This mechanism may have potential for predicting runners with susceptibility to injury

Children’s looking preference for biological motion may be related to an affinity for mathematical chaos

Recognition of biological motion is pervasive in early child development. Further, viewing the movement behavior of others is a primary component of a child’s acquisition of complex, robust movement repertoires, through imitation and real-time coordinated action. We theorize that inherent to biological movements are particular qualities of mathematical chaos and complexity. We further posit that this character affords the rich and complex inter-dynamics throughout early motor development. Specifically, we explored whether children’s preference for biological motion may be related to an affinity for mathematical chaos. Cross recurrence quantification analysis (cRQA) was used to investigate the coordination of gaze and posture with various temporal structures (periodic, chaotic, and aperiodic) of the motion of an oscillating visual stimulus. Children appear to competently perceive and respond to chaotic motion, both in rate (cRQA-percent determinism) and duration (cRQA-maxline) of coordination. We interpret this to indicate that children not only recognize chaotic motion structures, but also have a preference for coordination with them. Further, stratification of our sample (by age) uncovers the suggestion that this preference may become refined with age

KARST FEATURES AND RELATED SOCIAL PROCESSES IN THE REGION OF THE VIKOS GORGE AND TYMPHI MOUNTAIN (NORTHERN PINDOS NATIONAL PARK, GREECE)

Due to unfavourable natural conditions (poor soils, lack of water, special relief conditions), karst terrains have always been relatively sparsely populated, and they have been seriously affected by recent depopulation processes. However, the creation of national parks on karst terrains and the recent increase of (geo)tourism may influence and even turn these population trends. Our study examines the validity of this statement in the context of Vikos Gorge and Tymphi Mountain (NW Greece). Geological and geomorphological values are presented first, including Vikos Gorge, the glaciokarst landscape of Tymphi and the particular spherical rock concretions. Digital terrain analysis is used to obtain scientifically based, reliable morphometric parameters about Vikos Gorge, and it is found that the maximum gorge depth is 1144 m, the maximum width is 2420 m, and the maximum of depth/width ratio is 0.76. Thereafter, rural depopulation trends are examined and it is found that this region (Zagori) is seriously affected by depopulation. It is observed that there are differences among settlements, and a relative stabilization of population is sensible in only few settlements around Vikos Gorge, which are linked to tourism. As for nature protection, while at the beginning conflicts were perceptible among management and local people, now new conflicts are emerging between growing tourism and nature protection goals.Key words: gorge morphometry, glaciokarst, spherical concretions, rural depopulation, geotourism, national park.Kraške oblike in s krasom povezane družbene spremembe na območju soteske Vikos ter v gorovju Timfi (narodni park Severni Pindi, Grčija)Zaradi neugodnih naravnih razmer, kot so manj rodovitna prst, pomanjkanje vode in svojstvena oblikovanost površja, je kraško površje od nekdaj relativno redko poseljeno, v zadnjem obdobju pa je podvrženo tudi procesom odseljevanja. V zadnjem času je vse več tudi geoturizma in z njim povezanega ustanavljanja geoparkov, ki trend depopulacije lahko tudi obrnejo. Pričujoča študija se nanaša na vrednotenje omenjenih procesov na primeru doline Vikos in gorovja Timfi (SZ Grčija). Najprej so predstavljene geomorfološke in geološke značilnosti območja, kjer so izpostavljene značilnosti soteske Vikos, glaciokras gorovja Timfi in za to območje značilne okrogle skalne konkrecije. Digitalni model višin je bil namenjen morfometrični analizi soteske Vikos. Ta je pokazala, da je njena največja globina 1144 m, največja širina 2420 m, največje razmerje med globino in širino pa 0,76. V nadaljevanju so analizirane značilnosti odseljevanja s podeželja, katerim je najbolj podvrženo območje Zagori. Demografski vzorci kažejo na razlike med posameznimi naselji, kjer je število prebivalcev stabilno le v nekaterih naseljih v bližini turistično zanimive soteske Vikos. Z ustanovitvijo parka so se pojavili tudi konflikti. V začetku so se navzkrižja interesov pojavila med lokalnim prebivalstvom in upravljavci, sedaj pa se konflikt pojavlja ob istočasnem naraščanju turizma in želji po varovanju narave.Kjučne besede: morfometrija soteske, glaciokras, okrogle konkrecije, depopulacija podeželja, geoturizem, narodni park.

Indifference to Chaotic Motion May Be Related to Social Disinterest in Children With Autism

Children with autism spectrum disorder tend to have little interest in the presence, actions, and motives of other persons. In addition, these children tend to present with a limited and overly redundant movement repertoire, often expressing hyperfixation and aversion to novelty. We explore whether this is related to a more fundamental lack of appreciation for various temporal dynamics, including periodic, chaotic, and aperiodic motion structures. Seven children with ASD (age, gender, and height matched with children without ASD) were asked to stand and watch the motion of a visual stimulus displayed on a large (55 ) video monitor. Gaze and posture movements were recorded and assessed using cross recurrence quantification analysis for qualities of coordination, including rate and duration of bouts of coordination. Results showed that children with ASD do not express an affinity to chaotic motion of the stimulus in the same way as children without ASD. We contend that this indifference to chaotic motion is foundational to their general disinterest in biological motion

Aging and partial body weight support affects gait variability

This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

Intralimb coordination following obstacle clearance during running: the effect of obstacle height

The purpose of this study was to investigate the different coordination strategies used following obstacle clearance during running. Ten subjects ran over a level surface and over obstacles of six different heights (10, 12.5, 15, 17.5, 20 and 22.5% of their standing height). Analysis based upon the dynamical systems theory (DST) was used and the phasing relationships between lower extremity segments were examined. The results demonstrated that the increasing obstacle height elicited behavioral changes. The foot and the leg became more independent in their actions, while the leg and the thigh strengthened their already stable relationship. The 15% obstacle height seems to be a critical height for the observed changes

Center of pressure and the projection of the time-course of sitting skill acquisition

A normal time-course for the acquisition of sitting is essential. A delay in sitting may affect other developmental milestones, resulting in deficiencies in overall skill. Therefore, our aim was to identify variables whose measures at the very beginning of sitting would allow for the projection of the evolution of the sitting skill. Center of pressure data were collected from the postural sway of twenty-six typically developing infants while sitting on a force platform with a beginning ability to sit upright. Spatial, temporal and frequency variables of postural sway were obtained from both the medial/lateral and anterior/posterior directions of sway. Discriminant function analysis was conducted to identify potential predictors of the duration between onset and fully independent sitting. Gender (p=0.025), Median Frequency (p=0.006), and Correlation Dimension (p=0.002) were identified to be predictive of grouping with 73.1% correct classification of the participating infants into short, mid, and long delay groups. In conclusion, measures taken at the earliest stage of sitting may allow the projection of the time-course to achieve independent sitting for typical infants. This approach may be useful for monitoring typical development