Effects of surrogate feedback on the temporal coordination of sequential movements

Bei der Steuerung von Bewegungen verwendet das motorische System verschiedene Arten von Rückmeldungen, um die Präzision zu erhöhen. Dies lässt sich z.B. bei Greif- und Hebe-Bewegungen beobachten, bei denen die taktile Rückmeldung von den Fingerspitzen dazu genutzt wird, die Griffkraft zu regulieren. Dies ist nicht auf gleiche Modalitäten beschränkt -- so können z.B. auditive Rückmeldungen dazu genutzt werden, die Variabilität bei einer Tapping-Aufgabe zu senken. Eine zentrale Fragestellung im Kontext von Assistenzsystemen für Nutzer mit sensomotorischen Defiziten ist, ob künstlich erzeugte sensorische Rückmeldungen ebenfalls dazu genutzt werden können, die Präzision von Bewegungen zu verbessern. In dieser Arbeit wurden verschiedene Aspekte dieser Fragestellung anhand einer Tapping-Aufgabe untersucht. Hierzu wurden mehrere abhängige Variablen genutzt, z.B. globale Maße wie konstanter und variabler Fehler, aber auch Messungen der aufgewandten Kraft bei den Tapping-Bewegungen. Desweiteren wurde ein bekanntes Modell aus der psychologischen Grundlagenforschung eingesetzt: Das Zwei-Ebenen-Modell (WKM) von Wing und Kristofferson (1973b). Das WKM teilt die bei rhytmischen Bewegungen gemessene Variabilität in zwei Komponenten auf: Eine zentralnervöse Zeitgeber-Struktur und die motorischen Umsetzung. Neuere Studien zeigen, dass der zentrale Zeitgeber sensorisches Feedback integriert -- im Gegensatz zu der ursprünglichen Annahme von Wing und Kristofferson, die den Zeitgeber als offenen Regelkreis annahmen. Daher wurde in dieser Arbeit überprüft, ob sich das WKM eignet, um den Einfluss von künstlichen sensorischen Rückmeldungen auf die Variabilität zu modellieren. Experiment 1 zeigte, dass künstliche taktile Rückmeldungen sowohl am Zeigefinger als auch am großen Zeh integriert werden können, mit lediglich geringen Unterschieden. Experiment 2 erweiterte die Befunde, indem gezeigt wurde, dass taktile Rückmeldungen auch bis zu einem gewissen Grad die endogenen taktilen Rückmelddungen kompensieren können, wenn diese reduziert werden. Jedoch gab es in beiden Experimenten unerwartetes Verhalten der Schätzwerte für zentrale und periphere Varianz. In Experiment 2 wurde bestätigt, dass ca. ein Drittel aller Trials nicht die Modellannahmen erfüllten, was der Grund für das unerwartete Verhalten sein könnte. Um Vergleiche mit anderen Studien zu ermöglichen, wurde das Modell dennoch in den verbleibenden Experimenten angewandt. Die verbleibenden drei Experimente befassten sich mit Fragestellungen, die während Experiment 1 und 2 auftauchten. In Experiment 3 wurde untersucht, ob sich die Vertrautheit mit den künstlichen taktilen Rückmeldungen steigern lässt, wenn die Vorgabe der Tapping-Geschwindigkeit nicht durch Töne erfolgt, sondern ebenfalls durch taktile Pulse. Dies war nicht der Fall. Experiment 4 führte eine künstliche, systematisch variierte Verzögerung der künstlichen Rückmeldungen ein. Die Verzögerung war dazu gedacht, die Verlässlichkeit der künstlichen Rückmeldungen zu manipulieren. In den Maßen für zeitliche Präzision hatte dies bereits einen Effekt ab der niedrigsten Verzögerungsstufe. Bei den Kraftmaßen war der Effekt am ausgeprägtesten für mittlere Verzögerungsstufen. Die Verzögerung wurde bei Experiment 5 beibehalten, aber zusätzlich wurde neben den künstlichen taktilen Rückmeldungen auch auditive Rückmeldungen verwendet. Dies führte zu deutlich ausgeprägteren Effekten in sowohl den Zeit- als auch den Kraftmaßen. Außerdem wurden zwei Altersgruppen miteinander verglichen. Ältere Probanden zeigten im Ganzen eine mit den jüngeren Probanden vergleichbare Leistung bei den Maßen für zeitliche Präzision. Bei den Kraftmaßen zeigten sich hingegen klare Unterschiede zwischen beiden Altersgruppen. Zusammenfassend lässt sich sagen, dass die Befunde der Experimente in dieser Arbeit zur Literatur passen. Jedoch sprechen die häufigen Verletzungen der Modellannahmen sowie das unverwartete Verhalten der Schätzwerte für zentrale und periphere Varianz gegen die Anwendung des WKM um den Einfluß von künstlichem Feedback zu modellieren. Hierzu erwiesen sich die globalen Maße als geeigneter. Die Kraftmaße erschienen ebenfalls vielversprechend, bedürfen allerdings noch weiterer Erforschung vor einer eventuellen praktischen Anwendung.The human motor system integrates various sources of feedback to increase movement precision. This can be observed, for instance, when lifting an object with the thumb and index finger, where the tactile sensory feedback of the fingertips is being used to control the amount of grip force applied. Other modalities can be used as well (e.g., auditory feedback helps to produce more regular intervals in a tapping task). In the context of an assistance system for users with sensorimotor deficits, a general question is whether artificially generated sensory feedback can be used as surrogate sensory feedback to enhance movement precision. This thesis examined several aspects of this question by means of a tapping task. Several methods were chosen to evaluate whether the feedback was integrated. Global measures of timing precision (viz., constant and variable error), as well as measurement of the applied force at the tapping movements during the continuation phase were employed. Furthermore, a well-known model from basic psychological research, the two-level timing model for interresponse intervals by Wing and Kristofferson (1973b), was applied. The two-level timing model distinguishes a central timing structure and the motor implementation processes by partitioning the observed global interresponse interval variance into a central and a peripheral variance component. Recent studies showed that the central timing structure seems to integrate sensory feedback—despite that it was originally assumed as an open loop process. Therefore, it was assessed whether the two-level timing model is also suited to model the influence of surrogate sensory feedback on the timing of movements, and how the variance components are influenced under such circumstances. Experiment 1 showed that surrogate tactile feedback could be integrated when applied on both the finger and the hallux (big toe) with little differences. Experiment 2 extended the findings, showing that the surrogate tactile feedback could compensate for missing sensory reafferences to some extent. However, in both experiments, the estimators of the two-level timing model also showed unexpected behavior, such as an increase of the peripheral variance with target interval. In Experiment 2, it was confirmed that about a third of all trials did not met the model assumptions, which may be the cause for the unexpected behavior. To maintain comparability with a number of studies, the remaining experiments continued to apply the variance decomposition, despite the unmet assumptions. The remaining three experiments addressed questions which arose during Experiments 1 and 2. Experiment 3 investigated whether the pacing modality could increase the familiarity with the surrogate tactile feedback, if the tapping speed was also given using tactile pacing stimuli instead of audio stimuli. This was not the case. Experiment 4 introduced a systematically varied delay of the surrogate feedback signal in order to manipulate the perceived reliability. The delay manifested in the temporal measures already at the lowest level of delay. Furthermore, the force measures (e.g., amplitudes) indicated that the force regulation was most economic for mid-range values of the delay. Experiment 5 compared the influence of two different modalities (tactile vs. audio) across systematically varied delays. The effects of audio feedback were much more pronounced, on both the temporal and force measures. Furthermore, two different age groups were compared. The older adults generally performed comparable to the younger adults at the temporal measures. The force measures instead showed clear differences between both age groups in general but also regarding the integration of surrogate feedback in particular. To conclude, the effects found were generally in line with the literature. However, the problematic behavior of the estimators as well as the frequently unmet model assumptions oppose the application of the two-level timing model in this context. For evaluating the effect of surrogate sensory feedback, the global measures of timing precision performed better. Force measures also seemed promising, but require further research to increase understanding prior to application in a practical context

Time Series Analysis as a Method to Examine Acoustical Influences on Real-time Perception of Music

Multivariate analyses of dynamic correlations between continuous acoustic properties (intensity and spectral flatness) and real-time listener perceptions of change and expressed affect (arousal and valence) in music are developed, by an extensive application of autoregressive Time Series Analysis (TSA). TSA offers a large suite of techniques for modeling autocorrelated time series, such as constitute both music’s acoustic properties and its perceptual impacts. A logical analysis sequence from autoregressive integrated moving average regression with exogenous variables (ARIMAX), to vector autoregression (VAR) is established. Information criteria discriminate amongst models, and Granger Causality indicates whether a correlation might be a causal one. A 3 min electroacoustic extract from Wishart’s Red Bird is studied. It contains digitally generated and transformed sounds, and animate sounds, and our approach also permits an analysis of their impulse action on the temporal evolution and the variance in the perceptual time series. Intensity influences perceptions of change and expressed arousal substantially. Spectral flatness influences valence, while animate sounds influence the valence response and its variance. This TSA approach is applicable to a wide range of questions concerning acoustic- perceptual relationships in music

Influences of environmental stressors on autonomic function in 12-month-old infants: understanding early common pathways to atypical emotion regulation and cognitive performance

Background Previous research has suggested that children exposed to more early‐life stress show worse mental health outcomes and impaired cognitive performance in later life, but the mechanisms subserving these relationships remain poorly understood. Method Using miniaturised microphones and physiological arousal monitors (electrocardiography, heart rate variability and actigraphy), we examined for the first time infants’ autonomic reactions to environmental stressors (noise) in the home environment, in a sample of 82 12‐month‐old infants from mixed demographic backgrounds. The same infants also attended a laboratory testing battery where attention‐ and emotion‐eliciting stimuli were presented. We examined how children's environmental noise exposure levels at home related to their autonomic reactivity and to their behavioural performance in the laboratory. Results Individual differences in total noise exposure were independent of other socioeconomic and parenting variables. Children exposed to higher and more rapidly fluctuating environmental noise showed more unstable autonomic arousal patterns overall in home settings. In the laboratory testing battery, this group showed more labile and short‐lived autonomic changes in response to novel attention‐eliciting stimuli, along with reduced visual sustained attention. They also showed increased arousal lability in response to an emotional stressor. Conclusions Our results offer new insights into the mechanisms by which environmental noise exposure may confer increased risk of adverse mental health and impaired cognitive performance during later life

Workload characterization, modeling, and prediction in grid Computing

Workloads play an important role in experimental performance studies of computer systems. This thesis presents a comprehensive characterization of real workloads on production clusters and Grids. A variety of correlation structures and rich scaling behavior are identified in workload attributes such as job arrivals and run times, including pseudo-periodicity, long range dependence, and strong temporal locality. Based on the analytic results workload models are developed to fit the real data. For job arrivals three different kinds of autocorrelations are investigated. For short to middle range dependent data, Markov modulated Poisson processes (MMPP) are good models because they can capture correlations between interarrival times while remaining analytically tractable. For long range dependent and multifractal processes, the multifractal wavelet model (MWM) is able to reconstruct the scaling behavior and it provides a coherent wavelet framework for analysis and synthesis. Pseudo-periodicity is a special kind of autocorrelation and it can be modeled by a matching pursuit approach. For workload attributes such as run time a new model is proposed that can fit not only the marginal distribution but also the second order statistics such as the autocorrelation function (ACF). The development of workload models enable the simulation studies of Grid scheduling strategies. By using the synthetic traces, the performance impacts of workload correlations in Grid scheduling is quantitatively evaluated. The results indicate that autocorrelations in workload attributes can cause performance degradation, in some situations the difference can be up to several orders of magnitude. The larger the autocorrelation, the worse the performance, it is proved both at the cluster and Grid level. This study shows the importance of realistic workload models in performance evaluation studies. Regarding performance predictions, this thesis treats the targeted resources as a ``black box'' and takes a statistical approach. It is shown that statistical learning based methods, after a well-thought and fine-tuned design, are able to deliver good accuracy and performance.UBL - phd migration 201

Dependence-driven techniques in system design

Burstiness in workloads is often found in multi-tier architectures, storage systems, and communication networks. This feature is extremely important in system design because it can significantly degrade system performance and availability. This dissertation focuses on how to use knowledge of burstiness to develop new techniques and tools for performance prediction, scheduling, and resource allocation under bursty workload conditions.;For multi-tier enterprise systems, burstiness in the service times is catastrophic for performance. Via detailed experimentation, we identify the cause of performance degradation on the persistent bottleneck switch among various servers. This results in an unstable behavior that cannot be captured by existing capacity planning models. In this dissertation, beyond identifying the cause and effects of bottleneck switch in multi-tier systems, we also propose modifications to the classic TPC-W benchmark to emulate bursty arrivals in multi-tier systems.;This dissertation also demonstrates how burstiness can be used to improve system performance. Two dependence-driven scheduling policies, SWAP and ALoC, are developed. These general scheduling policies counteract burstiness in workloads and maintain high availability by delaying selected requests that contribute to burstiness. Extensive experiments show that both SWAP and ALoC achieve good estimates of service times based on the knowledge of burstiness in the service process. as a result, SWAP successfully approximates the shortest job first (SJF) scheduling without requiring a priori information of job service times. ALoC adaptively controls system load by infinitely delaying only a small fraction of the incoming requests.;The knowledge of burstiness can also be used to forecast the length of idle intervals in storage systems. In practice, background activities are scheduled during system idle times. The scheduling of background jobs is crucial in terms of the performance degradation of foreground jobs and the utilization of idle times. In this dissertation, new background scheduling schemes are designed to determine when and for how long idle times can be used for serving background jobs, without violating predefined performance targets of foreground jobs. Extensive trace-driven simulation results illustrate that the proposed schemes are effective and robust in a wide range of system conditions. Furthermore, if there is burstiness within idle times, then maintenance features like disk scrubbing and intra-disk data redundancy can be successfully scheduled as background activities during idle times

Audio source separation for music in low-latency and high-latency scenarios

Aquesta tesi proposa mètodes per tractar les limitacions de les tècniques existents de separació de fonts musicals en condicions de baixa i alta latència. En primer lloc, ens centrem en els mètodes amb un baix cost computacional i baixa latència. Proposem l'ús de la regularització de Tikhonov com a mètode de descomposició de l'espectre en el context de baixa latència. El comparem amb les tècniques existents en tasques d'estimació i seguiment dels tons, que són passos crucials en molts mètodes de separació. A continuació utilitzem i avaluem el mètode de descomposició de l'espectre en tasques de separació de veu cantada, baix i percussió. En segon lloc, proposem diversos mètodes d'alta latència que milloren la separació de la veu cantada, gràcies al modelatge de components específics, com la respiració i les consonants. Finalment, explorem l'ús de correlacions temporals i anotacions manuals per millorar la separació dels instruments de percussió i dels senyals musicals polifònics complexes.Esta tesis propone métodos para tratar las limitaciones de las técnicas existentes de separación de fuentes musicales en condiciones de baja y alta latencia. En primer lugar, nos centramos en los métodos con un bajo coste computacional y baja latencia. Proponemos el uso de la regularización de Tikhonov como método de descomposición del espectro en el contexto de baja latencia. Lo comparamos con las técnicas existentes en tareas de estimación y seguimiento de los tonos, que son pasos cruciales en muchos métodos de separación. A continuación utilizamos y evaluamos el método de descomposición del espectro en tareas de separación de voz cantada, bajo y percusión. En segundo lugar, proponemos varios métodos de alta latencia que mejoran la separación de la voz cantada, gracias al modelado de componentes que a menudo no se toman en cuenta, como la respiración y las consonantes. Finalmente, exploramos el uso de correlaciones temporales y anotaciones manuales para mejorar la separación de los instrumentos de percusión y señales musicales polifónicas complejas.This thesis proposes specific methods to address the limitations of current music source separation methods in low-latency and high-latency scenarios. First, we focus on methods with low computational cost and low latency. We propose the use of Tikhonov regularization as a method for spectrum decomposition in the low-latency context. We compare it to existing techniques in pitch estimation and tracking tasks, crucial steps in many separation methods. We then use the proposed spectrum decomposition method in low-latency separation tasks targeting singing voice, bass and drums. Second, we propose several high-latency methods that improve the separation of singing voice by modeling components that are often not accounted for, such as breathiness and consonants. Finally, we explore using temporal correlations and human annotations to enhance the separation of drums and complex polyphonic music signals