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Trade-off between frequency and precision during stepping movements: Kinematic and BOLD brain activation patterns.

ABSTRACT: The central nervous system has the ability to adapt our locomotor pattern to produce a wide range of gait modalities and velocities. In reacting to external pacing stimuli, deviations from an individual preferred cadence provoke a concurrent decrease in accuracy that suggests the existence of a trade-off between frequency and precision; a compromise that could result from the specialization within the control centers of locomotion to ensure a stable transition and optimal adaptation to changing environment. Here, we explore the neural correlates of such adaptive mechanisms by visually guiding a group of healthy subjects to follow three comfortable stepping frequencies while simultaneously recording their BOLD responses and lower limb kinematics with the use of a custom-built treadmill device. In following the visual stimuli, subjects adopt a common pattern of symmetric and anti-phase movements across pace conditions. However, when increasing the stimulus frequency, an improvement in motor performance (precision and stability) was found, which suggests a change in the control mode from reactive to predictive schemes. Brain activity patterns showed similar BOLD responses across pace conditions though significant differences were observed in parietal and cerebellar regions. Neural correlates of stepping precision were found in the insula, cerebellum, dorsolateral pons and inferior olivary nucleus, whereas neural correlates of stepping stability were found in a distributed network, suggesting a transition in the control strategy across the stimulated range of frequencies: from unstable/reactive at lower paces (i.e., stepping stability managed by subcortical regions) to stable/predictive at higher paces (i.e., stability managed by cortical regions). Hum Brain Mapp 37:1722-1737, 2016. © 2016 Wiley Periodicals, Inc.

SUBMITTER: Martinez M

PROVIDER: S-EPMC6867488 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature

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Trade-off between frequency and precision during stepping movements: Kinematic and BOLD brain activation patterns.

Martínez Martin M Valencia Miguel M Vidorreta Marta M Luis Elkin O EO Castellanos Gabriel G Villagra Federico F Fernández-Seara Maria A MA Pastor Maria A MA

Human brain mapping 20160209 5

The central nervous system has the ability to adapt our locomotor pattern to produce a wide range of gait modalities and velocities. In reacting to external pacing stimuli, deviations from an individual preferred cadence provoke a concurrent decrease in accuracy that suggests the existence of a trade-off between frequency and precision; a compromise that could result from the specialization within the control centers of locomotion to ensure a stable transition and optimal adaptation to changing ...[more]

PMID: 26857613

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Project description:BackgroundAlthough deficits in the interpretation of affective facial expressions have been described clinically and in behavioral studies of fetal alcohol spectrum disorders (FASD), effects of prenatal alcohol exposure on the neural networks that mediate affective appraisal have not previously been examined.MethodsWe administered a nonverbal event-related fMRI affective appraisal paradigm to 64 children (mean age = 12.5 years; 18 with fetal alcohol syndrome (FAS) or partial FAS (PFAS), 18 nonsyndromal heavily exposed (HE), and 28 controls). Happy, sad, angry, fearful, and neutral faces and pixelated control images were presented sequentially in a randomized order. The child indicated whether the currently displayed face showed the same or different affect as the previous one.ResultsData from whole-brain analyses showed that all groups activated the appropriate face processing neural networks. Region of interest analyses indicated that, compared to HE and control children, the FAS/PFAS group exhibited greater blood oxygenation level-dependent (BOLD) signal changes when processing neutral faces than pixelated images in 2 regions that form part of the visual sensory social brain network, which plays an important role in the initial processing of facial affect. By contrast, BOLD signal when processing angry faces was weaker for the FAS/PFAS group in a region involved in the processing of facial identity and facial expressions and in a region involved in the recognition and selection of behavioral responses to aggressive behavior.ConclusionsThese findings of greater BOLD signal in the FAS/PFAS group in response to neutral faces suggest less efficient neural processing of more difficult to interpret emotions, and the weaker BOLD response to angry faces suggests altered processing of angry stimuli. Although behavioral performance did not differ in this relatively simple affective appraisal task, these data suggest that in children with FAS and PFAS, the appraisal of neutral affect and anger is likely to be more effortful in more challenging and dynamic social contexts.

Project description:BackgroundSoft wearable robots (exosuits), being lightweight, ergonomic and low power-demanding, are attractive for a variety of applications, ranging from strength augmentation in industrial scenarios, to medical assistance for people with motor impairments. Understanding how these devices affect the physiology and mechanics of human movements is fundamental for quantifying their benefits and drawbacks, assessing their suitability for different applications and guiding a continuous design refinement.MethodsWe present a novel wearable exosuit for assistance/augmentation of the elbow and introduce a controller that compensates for gravitational forces acting on the limb while allowing the suit to cooperatively move with its wearer. Eight healthy subjects wore the exosuit and performed elbow movements in two conditions: with assistance from the device (powered) and without assistance (unpowered). The test included a dynamic task, to evaluate the impact of the assistance on the kinematics and dynamics of human movement, and an isometric task, to assess its influence on the onset of muscular fatigue.ResultsPowered movements showed a low but significant degradation in accuracy and smoothness when compared to the unpowered ones. The degradation in kinematics was accompanied by an average reduction of 59.20±5.58% (mean ± standard error) of the biological torque and 64.8±7.66% drop in muscular effort when the exosuit assisted its wearer. Furthermore, an analysis of the electromyographic signals of the biceps brachii during the isometric task revealed that the exosuit delays the onset of muscular fatigue.ConclusionsThe study examined the effects of an exosuit on the characteristics of human movements. The suit supports most of the power needed to move and reduces the effort that the subject needs to exert to counteract gravity in a static posture, delaying the onset of muscular fatigue. We interpret the decline in kinematic performance as a technical limitation of the current device. This work suggests that a powered exosuit can be a good candidate for industrial and clinical applications, where task efficiency and hardware transparency are paramount.

Dataset Information

Trade-off between frequency and precision during stepping movements: Kinematic and BOLD brain activation patterns.

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Trade-off between frequency and precision during stepping movements: Kinematic and BOLD brain activation patterns.

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