Does the motor system need intermittent control?

Explanation of motor control is dominated by continuous neurophysiological pathways (e.g. trans-cortical, spinal) and the continuous control paradigm. Using new theoretical development, methodology and evidence, we propose intermittent control, which incorporates a serial ballistic process within the main feedback loop, provides a more general and more accurate paradigm necessary to explain attributes highly advantageous for competitive survival and performance

Long-term follow-up and treatment in nine boys with X-linked creatine transporter defect

The creatine transporter (CRTR) defect is a recently discovered cause of X-linked intellectual disability for which treatment options have been explored. Creatine monotherapy has not proved effective, and the effect of treatment with L-arginine is still controversial. Nine boys between 8 months and 10 years old with molecularly confirmed CRTR defect were followed with repeated 1H-MRS and neuropsychological assessments during 4–6 years of combination treatment with creatine monohydrate, L-arginine, and glycine. Treatment did not lead to a significant increase in cerebral creatine content as observed with H1-MRS. After an initial improvement in locomotor and personal-social IQ subscales, no lasting clinical improvement was recorded. Additionally, we noticed an age-related decline in IQ subscales in boys affected with the CRTR defect

Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular "reactive oxygen species" (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation. We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation). The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible. This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference

Getting a grip on grasping

Grasping enables humans to get a grip on a variety of surrounding things. In his thesis, Cornelis van de Kamp describes a number of experiments studying grasping behavior. The aim of his thesis is to get a better understanding of how grasping movements are controlled in catching and prehension movements. The studies on catching and prehension are focused on the question what are the controlled variables, what information do we use, and what is the control law relating the information to the controlled variable. This dissertation proposes a dynamic-tau model which based on time-to-contact information provides an accurate description of the timing of the initiation of hand closure in both catching and prehension.

Prehension is really reaching and grasping

Prehension has traditionally been seen as the act of coordinated reaching and grasping. However, recently, Smeets and Brenner (in Motor Control 3:237-271, 1999) proposed that we might just as well look at prehension as the combination of two independently moving digits. The hand aperture that has featured prominently in many studies on prehension, according to Smeets and Brenner's "double-pointing hypothesis", is really an emergent property related to the time course of the positions of the two digits moving to their respective end points. We tested this double-pointing hypothesis by perturbing the end position of one of the digits while leaving the end position of the opposing digit unchanged. To this end, we had participants reach for and grasp a metallic object of which the side surfaces could be made to slide in and out. We administered the perturbation right after movement initiation. On several occasions, after perturbing the end position of one digit, we found effects also on the kinematics of the opposing digit. These findings are in conflict with Smeets and Brenner's double-pointing hypothesis

Dataset accompanying publication "Is intermittent control the source of the nonlinear oscillatory component (0.2-2Hz) in human balance control?"

This dataset supports the publication "Is intermittent control the source of the nonlinear oscillatory component (0.2-2Hz) in human balance control". The data includes the experimental signals (input disturbance d, myoelectric control signal ue and the system output (position) y, raw EMG), transfer functions for the external and neuromuscular system, and trial descriptors required for readers to investigate the experimental data using their own methods and models. The dataset includes MATLAB code for the cost function to enable readers to compare their own results with those reported in this publication. The dataset includes 68 trials, from 14 healthy participants. Each participant attempted five 250s trials in randomized order including eyes open unstable (EO US), eyes closed unstable (EC US), eyes open stable (EO S), eyes closed stable (EC S), lower amplitude disturbance eyes open unstable (L EO US). The instructions are contained within the file ‘Instructions for DataSet.docx’ and the data, which can be opened in MATLAB once downloaded, is contained in ‘PublicationDataSet.mat’