Neural control on multiple time scales: Insights from human stick balancing

The time-delayed feedback control mechanisms of the nervous system are continuously subjected to the effects of uncontrolled random perturbations (herein referred to as noise). In this setting the statistical properties of the fluctuations in the controlled variable(s) can provide non-invasive insights into the nature of the underlying control mechanisms. We illustrate this concept through a study of stick balancing at the fingertip using high speed motion capture techniques. Experimental observations together with numerical studies of a stochastic delay differential equation demonstrate that on time scales short compared to the neural time delay ("fast control"), parametric noise provides a non-predictive mechanism that transiently stabilizes the upright position of the balanced stick. Moreover, numerical simulations of a delayed random walker with a repulsive origin indicate that even an unstable fixed point can be transiently stabilized by the interplay between noise and time delay. In contrast, on time scales comparable to the neural time delay ("slow control"), feedback and feedforward control mechanisms become more important. The relative contribution of the fast and slow control mechanisms to stick balancing is dynamic and, for example, depends on the context in which stick balancing is performed and the expertise of the balancer

Major Social Issues: A Multidisciplinary View

xvi,497 hal,:25cm.;index

Ferredoxin-thioredoxin reductase: Properties of its complex with ferredoxin

International audienc

Towards a multilingual preschool policy : a linguistic ethnographic analysis of the implementation of a transformative pedagogy

The effects of immersive strategies and the benefits of a multilingual language policy have been extensively explored in the literature; however, it is valuable to look at the actual application of a multilingual policy. Putting linguistic-educational research into practice by implementing a transformative pedagogical approach is characterized by a process of trial and error, which has remained understudied. This chapter aims to fill this gap by adopting a case study approach that focuses on the implementation of a multilingual/cultural policy at a preschool in the Dutch-speaking part of Belgium. More than half of the children attending the preschool come from a multilingual background. Based on ethnographic fieldwork, consisting of observations, participations, interviews, and focus group discussions with different stakeholders, this chapter analyzes the mechanisms behind the preschool's switch from negatively undergoing multilingualism to positively engaging with it