Magnus Liebherr

Detrended fluctuation analysis and adaptive fractal analysis of stride time data in Parkinson's disease: stitching together short gait trials.

Variability indicates motor control disturbances and is suitable to identify gait pathologies. It can be quantified by linear parameters (amplitude estimators) and more sophisticated nonlinear methods (structural information). Detrended Fluctuation Analysis (DFA) is one method to measure structural information, e.g., from stride time series. Recently, an improved method, Adaptive Fractal Analysis (AFA), has been proposed. This method has not been applied to gait data before. Fractal scaling methods (FS) require long stride-to-stride data to obtain valid results. However, in clinical studies, it is not usual to measure a large number of strides (e.g., strides). Amongst others, clinical gait analysis is limited due to short walkways, thus, FS seem to be inapplicable. The purpose of the present study was to evaluate FS under clinical conditions. Stride time data of five self-paced walking trials ( strides each) of subjects with PD and a healthy control group (CG) was measured. To generate longer time series, stride time sequences were stitched together. The coefficient of variation (CV), fractal scaling exponents (DFA) and (AFA) were calculated. Two surrogate tests were performed: A) the whole time series was randomly shuffled; B) the single trials were randomly shuffled separately and afterwards stitched together. CV did not discriminate between PD and CG. However, significant differences between PD and CG were found concerning and . Surrogate version B yielded a higher mean squared error and empirical quantiles than version A. Hence, we conclude that the stitching procedure creates an artificial structure resulting in an overestimation of true . The method of stitching together sections of gait seems to be appropriate in order to distinguish between PD and CG with FS. It provides an approach to integrate FS as standard in clinical gait analysis and to overcome limitations such as short walkways.

Adherence to Worksite Health Interventions: Practical Recommendations Based on a Theoretical Framework

Health promotion at the workplace aims at environmental and/or behavioral changes. Numerous health promotion programs have shown positive effects on employees’ health and productivity. However, success is affected by insufficient adherence to long-term change of behavior. This article provides an overview of factors that influence employees’ adherence to worksite health interventions (WHIs). Strategies to enhance participation and adherence are outlined based on a review of the current literature. The findings are evaluated by reference to the health action process approach. We propose a theoretical framework for WHIs and make recommendations for supporting workers’ adherence to behavioral changes based on this model.

Dual-tasking and aging—About multiple perspectives and possible implementations in interventions for the elderly

Abstract It is well known that dual-tasking is adversely affected by physiological degenerative processes. Furthermore, the completion of a secondary task while walking is frequently discussed as a key contributor for falls in the elderly. Age-related differences in both activated neural structures and human behavior are indicated in numerous previous studies. Besides a general overview of dual-tasking and aging, this article reviews studies aiming at improving gait or postural control in older adults using dual- or multi-task interventions. Approximately, 130 parameters out of 17 illustrated studies presented significant changes after dual-task-specific interventions regarding gait, postural control/balance, and falls. On the one hand, the article at hand shows highly consistent results in all of the dual-task intervention studies analyzed, indicating significant improvements related to postural control, gait, falls, or the performance of a secondary task. On the other hand, the results represent a heterogeneous structure and a gap between theoretical aspects and practical use. To optimize the use of dual-task, a systematization of underlying tasks is inevitable and should be focused on in further research.

Cognitive performance under motor demands – On the influence of task difficulty and postural control

We often walk around when we have to think about something, but suddenly stop when we are confronted with a demanding cognitive task, such as calculating 1540*24. While previous neurophysiological research investigated cognitive and motor performance separately, findings that combine both are rare. To get a deeper understanding of the influence of motor demands as well as the difficulty of a simultaneously performed cognitive task, we investigated 20 healthy individuals. Participants performed two cognitive tasks with different levels of difficulty while sitting or standing on one leg. In addition to behavioral data, we recorded the electroencephalogram from 26Ag/AgCI scalp electrodes. The critical time-windows, predefined by visual inspection, yielded an early (200-300 ms, P2) and a subsequent positivity (350-500 ms, P3). Statistical analysis of the early time window registered a motor × cognition interaction. Resolution of this interaction revealed an effect of the cognitive task in the one-legged stance motor condition, with a more pronounced positivity for the difficult task. No significant differences between cognitive tasks emerged for the simple motor condition. The time-window between 350 and 500 ms registered main effects of the motor task and a trend for the cognitive task. While the influence of cognitive task difficulty (in the P3) is in accordance with previous studies, the motor task effect is specific to one-legged stance (cf. no effects for running in previous research). The motor-cognition interaction found in the P2 indicates that the more difficult motor task (one-legged stance) facilitates cognitive task performance.

Decision Making under Ambiguity and Objective Risk in Higher Age – A Review on Cognitive and Emotional Contributions

The ability of decision making plays a highly relevant role in our survival, but is adversely affected during the process of aging. The present review aims to provide a better understanding of age-related differences in decision making and the role of cognitive and emotional factors in this context. We reviewed the literature about age-effects on decision-making performance, focusing on decision making under ambiguous and objective risk. In decisions under ambiguous risks, as measured by the Iowa Gambling Task, decisions are based on the experiences with consequences. In this case, many articles have attributed age-related impairments in decision making to changes in emotional and somatic reward- and punishment processing. In decisions under objective risks, as measured for example by the Game of Dice Task, decisions can be based on explicit information about risks and consequences. In this case, age-related changes have been attributed mainly to a cognitive decline, particularly impaired executive functions. However, recent findings challenge these conclusions. The present review summarizes neuropsychological and neurophysiological findings of age-related differences in decision making under ambiguous and objective risk. In this context, the relevance of learning, but also of cognitive and emotional contributors – responsible for age-related differences in decision making – are additionally pointed out.

The Impact of Psychological and Demographic Parameters on Simulator Sickness.

In a world, which is characterized by technical progress, virtual environment technologies become increasingly relevant. In this context, simulators are used as a cost and time efficient methods for investigating innovative developments, training effects, but also the influence of individual attributes such as the process of aging. Although the simulator technologies have been greatly developed in recent years, they are not able to perfectly replicate the real world, which causes problems of system adaptation and simulator sickness. In the paper at hand, we will focus both, the time of adaptation to the virtual environment and the phenomenon of simulator sickness under the aspect of mental abilities and the process of aging, based on a driving simulator study with

Simultaneous motor demands affect decision making under objective risk

ABSTRACT Previous studies on factors influencing decision making focused on the effects of additional cognitive load, stress, psychological disorders, and the process of aging. The potential effects of simultaneously performing motor demands have been neglected, so far. However, previous motor / cognitive dual-task studies provide evidence for both negative as well as facilitating effects of simultaneously performing cognitive and motor tasks. The study at hand, aimed to investigate the effects of decision making under objective risk while performing additional motor demands. Seventy-two participants ranging from 18 to 30 years performed the Game of Dice Task either while sitting or while standing on one leg. Participants were asked to put similar effort on the decision task and the motor demand. The results revealed a significant main effect for “choice”, as well as a significant interaction of “choice” × “group”. Participants standing on one leg more frequently selected the most disadvantageous choice (one single number), whereas the “sitting group” most often selected the advantageous combination of four numbers. The findings are discussed under the aspects of executive functions, working memory, stress, somatic markers and the dual-process theory.

Bewegungssteuerung und -training bei Morbus Parkinson

Bewegungs- und Trainingsprogramme weisen ein bedeutendes Potenzial bei der Behandlung von Morbus Parkinson auf. Vor allem durch gezielt variable Trainingsinhalte konnen hier krankheitsbedingte Storungen im Bereich der Gang- und Gleichgewichtsmotorik reduziert werden. Zudem gibt es Hinweise, dass ein solches Bewegungstraining uber die Freisetzung neurotropher Faktoren neuroprotektive Funktionen hat. Die Ubersicht erlautert die aktuelle Studienlage zur Bewegungsvariabilitat und gibt einen Ausblick auf infrage kommende Trainingsansatze.