Rosemarie Velik

Abstract: Freezing of gait is a phenomenon common in Parkinson's patients and significantly affects quality of life. Sensory cues have been known to improve walking performance and reduce freezing of gait. Visual cues are reported to be particularly effective for this purpose. So far, sensory cues have generally been provided continuously, even when currently not needed. However, a recent approach suggests the provision of cues just in the case that freezing actually occurs. The arguments in favor of this "on-demand" cueing are reduced intrusiveness and reduced habituation to cues. Here, we analyzed the effect of visual cues on the number and duration of freezing episodes when activated either just "on-demand" or continuously and compare it to the baseline condition where no cue is provided. For this purpose, 7 Parkinson's patients regularly suffering from freezing of gait repeatedly walked a pre-defined course and their reaction to parallel laser lines projected in front of them on the floor was analyzed. The results show that, in comparison to the baseline condition, the mean duration of freezing was reduced by 51% in continuous cueing and by 69% in "on-demand" cueing. Concerning the number of freezing episodes, 43% fewer episodes were observed for continuous cueing and 9% less episodes for "on-demand" cueing.

Abstract: The binding problem in perception is concerned with answering the question how information from millions of sensory receptors, processed by millions of neurons working in parallel, can be merged into a unified percept. Binding in perception reaches from the lowest levels of feature binding up to the levels of multimodal binding of information coming from the different sensor modalities and also from other functional systems. The last 40 years of research have shown that the binding problem cannot be solved easily. Today, it is considered as one of the key questions to brain understanding. To date, various solutions have been suggested to the binding problem including: (1) combination coding, (2) binding by synchrony, (3) population coding, (4) binding by attention, (5) binding by knowledge, expectation, and memory, (6) hardwired vs. on-demand binding, (7) bundling and binding of features, (8) the feature-integration theory of attention, and (9) synchronization through top-down processes. Each of those hypotheses addresses important aspects of binding. However, each of them also suffers from certain weak points and can never give a complete explanation. This article gives a brief overview of the so far suggested solutions of perceptual binding and then shows that those are actually not mutually exclusive but can complement each other. A computationally verified model is presented which shows that, most likely, the different described mechanisms of binding act (1) at different hierarchical levels and (2) in different stages of "perceptual knowledge acquisition." The model furthermore considers and explains a number of inhibitory "filter mechanisms" that suppress the activation of inappropriate or currently irrelevant information.

Abstract: In robotic rehabilitation, the way of attaching the robotic device to the users' limb constitutes a crucial element of product quality, particularly for assuring good fitting, comfort, accuracy, usability, and safety. In this article, we present a new technological concept - 'Variable Stiffness Structure' - allowing for an improvement of these aspects in the 'robotic device to limb' - connection by offering a compound of materials that are together able to switch from a flexible textile-like state to a more rigid state by applying negative pressure. The paper describes the concept and the basic behaviour of the material, based on experiments.