Basic and Translational Neuroscience of Childhood-Onset Dystonia: A Control-Theory Perspective

2018 ◽  
Vol 41 (1) ◽  
pp. 41-59 ◽  
Author(s):  
Terence D. Sanger
Keyword(s):  
Muscle Activation ◽  
Distributed Network ◽  
Childhood Onset ◽  
Specific Mechanism ◽  
Involuntary Muscle ◽  
Postural Stabilization ◽  
Reflex Gain ◽  
Cortical Regions ◽  
Mechanism Of Failure ◽  
The Relationship

Dystonia is a collection of symptoms with involuntary muscle activation causing hypertonia, hyperkinetic movements, and overflow. In children, dystonia can have numerous etiologies with varying neuroanatomic distribution. The semiology of dystonia can be explained by gain-of-function failure of a feedback controller that is responsible for stabilizing posture and movement. Because postural control is maintained by a widely distributed network, many different anatomic regions may be responsible for symptoms of dystonia, although all features of dystonia can be explained by uncontrolled activation or hypersensitivity of motor cortical regions that can cause increased reflex gain, inserted postures, or sensitivity to irrelevant sensory variables. Effective treatment of dystonia in children requires an understanding of the relationship between etiology, anatomy, and the specific mechanism of failure of postural stabilization.

The relationship between muscle activation and handwriting quality with non-native grip styles

2021 ◽  
Author(s):  
Kristen M. Farris ◽  
Regan E. Fehrenbacher ◽  
Erin L. Hayes ◽  
Ryan R. McEvoy ◽  
Alex P. Smith ◽  
...  
Keyword(s):  
Muscle Activation ◽  
The Relationship

Could Different Directions of Infant Stepping Be Controlled by the Same Locomotor Central Pattern Generator?

2000 ◽  
Vol 83 (5) ◽  
pp. 2814-2824 ◽  
Author(s):  
Tania Lamb ◽  
Jaynie F. Yang
Keyword(s):  
Central Pattern Generator ◽  
Muscle Activation ◽  
Pattern Generator ◽  
Swing Phase ◽  
Smooth Transition ◽  
Cycle Duration ◽  
Human Infants ◽  
Activation Patterns ◽  
Muscle Activation Patterns ◽  
The Relationship

This study examined the idea of whether the same central pattern generator (CPG) for locomotion can control different directions of walking in humans. Fifty-two infants, aged 2–11 mo, were tested. Infants were supported to walk on a treadmill at a variety of speeds. If forward stepping was elicited, stepping in the other directions (primarily sideways and backward) was attempted. The orientation of the infant on the treadmill belt determined the direction of stepping. In some infants, we also attempted to obtain a smooth transition from one direction to another by gradually changing the orientation of the infant during a stepping sequence. Limb segment motion and surface electromyography from the muscles of the lower limb were recorded. Most infants who showed sustained forward walking also could walk in all other directions. Thirty-three of 34 infants tested could step sideways. The success of eliciting backward stepping was 69%. Most of the infants who did not meet our backward stepping criteria did, however, make stepping movements. The different directions of stepping had similar responses to changes in treadmill speed. The relationship between stance and swing phase durations and cycle duration were the same regardless of the direction of stepping across a range of speeds. Some differences were noted in the muscle activation patterns during different directions of walking. For example, the hamstrings were much more active during the swing phase of backward walking compared with forward walking. The quadriceps was more active in the trailing leg during sideways walking. In some infants, we were able to elicit stepping along a continuum of directions. We found no discrete differences in either the electromyographic patterns or the temporal parameters of stepping as the direction of stepping was gradually changed. The results support the idea that the same locomotor CPG controls different directions of stepping in human infants. The fact that most infants were able to step in all directions, the similarity in the response to speed changes, and the absence of any discrete changes as the direction of stepping was changed gradually are all consistent with this hypothesis.

scholarly journals Self-reported Sleep Problems Related to Amyloid Deposition in Cortical Regions with High HOMER1 Gene Expression

2019 ◽  
Vol 30 (4) ◽  
pp. 2144-2156 ◽  
Author(s):  
Anders M Fjell ◽  
Donatas Sederevicius ◽  
Markus H Sneve ◽  
Ann-Marie Glasø de Lange ◽  
Anne CecilieSjøli Bråthen ◽  
...  
Keyword(s):  
Sleep Quality ◽  
Sleep Problems ◽  
Older Individuals ◽  
Accumulation Pattern ◽  
Anatomical Distribution ◽  
Healthy Older Adults ◽  
Amyloid Aβ ◽  
Β Amyloid ◽  
Cortical Regions ◽  
The Relationship

Abstract Sleep problems are related to the elevated levels of the Alzheimer’s disease (AD) biomarker β-amyloid (Aβ). Hypotheses about the causes of this relationship can be generated from molecular markers of sleep problems identified in rodents. A major marker of sleep deprivation is Homer1a, a neural protein coded by the HOMER1 gene, which has also been implicated in brain Aβ accumulation. Here, we tested whether the relationship between cortical Aβ accumulation and self-reported sleep quality, as well as changes in sleep quality over 3 years, was stronger in cortical regions with high HOMER1 mRNA expression levels. In a sample of 154 cognitively healthy older adults, Aβ correlated with poorer sleep quality cross-sectionally and longitudinally (n = 62), but more strongly in the younger than in older individuals. Effects were mainly found in regions with high expression of HOMER1. The anatomical distribution of the sleep-Aβ relationship followed closely the Aβ accumulation pattern in 69 patients with mild cognitive impairment or AD. Thus, the results indicate that the relationship between sleep problems and Aβ accumulation may involve Homer1 activity in the cortical regions, where harbor Aβ deposits in AD. The findings may advance our understanding of the relationship between sleep problems and AD risk.

The Absence of Norm Modification and the Intensification of Norm Contestation: Africa and the Responsibility to Prosecute

2019 ◽  
Vol 11 (2) ◽  
pp. 172-197 ◽  
Author(s):  
Antonio Arcudi
Keyword(s):  
International Criminal Court ◽  
International Criminal ◽  
Criminal Court ◽  
Main Argument ◽  
Specific Mechanism ◽  
The Subject ◽  
The Relationship

In recent norm research, the question of the relationship between norm contestation and norm dynamics has been the subject of substantial debate. However, until now too little attention has been paid to the question of how and when contestation intensifies. Based on the differentiation between applicatory and validity contestation, this article proposes a specific mechanism for intensifying contestation—understood as an increase in the contestation itself as well as an extension to its validity level—by treating norm modification as an intervening variable. The main argument is that norm modification may be necessary to reconcile different interpretations of norms. Consequently, if norm modification does not occur, norm contestation may intensify. This article elaborates this mechanism by examining the controversies involving the International Criminal Court (icc). It shows that contestation began at a low and applicatory level but intensified after several attempts at norm modification had failed.

scholarly journals Using AI Methods to Evaluate a Minimal Model for Perception

2019 ◽  
Vol 2 (1) ◽  
pp. 503-524 ◽  
Author(s):  
Robert Prentner ◽  
Chris Fields
Keyword(s):  
Conceptual Understanding ◽  
Single Agent ◽  
Psychological Problem ◽  
Machine Learning Techniques ◽  
Distributed Network ◽  
Perceptual Inference ◽  
Interacting Agents ◽  
Learning Techniques ◽  
The Relationship

AbstractThe relationship between philosophy and research on artificial intelligence (AI) has been difficult since its beginning, with mutual misunderstanding and sometimes even hostility. By contrast, we show how an approach informed by both philosophy and AI can be productive. After reviewing some popular frameworks for computation and learning, we apply the AI methodology of “build it and see” to tackle the philosophical and psychological problem of characterizing perception as distinct from sensation. Our model comprises a network of very simple, but interacting agents which have binary experiences of the “yes/no”-type and communicate their experiences with each other. When does such a network refer to a single agent instead of a distributed network of entities? We apply machine learning techniques to address the following related questions: i) how can the model explain stability of compound entities, and ii) how could the model implement a single task such as perceptual inference? We thereby find consistency with previous work on “interface” strategies from perception research.While this reflects some necessary conditions for the ascription of agency, we suggest that it is not sufficient. Here, AI research, if it is intended to contribute to conceptual understanding, would benefit from issues previously raised by philosophy. We thus conclude the article with a discussion of action-selection, the role of embodiment, and consciousness to make this more explicit. We conjecture that a combination of AI research and philosophy allows general principles of mind and being to emerge from a “quasi-empirical” investigation.

Local Thinning at a Die Entry Radius During Hot Gas-Pressure Forming of an AA5083 Sheet

2010 ◽  
Vol 132 (1) ◽  
Author(s):  
Eric M. Taleff ◽  
Louis G. Hector ◽  
John R. Bradley ◽  
Ravi Verma ◽  
Paul E. Krajewski
Keyword(s):  
Sheet Material ◽  
Sheet Thickness ◽  
Gas Pressure ◽  
Die Geometry ◽  
Fine Grained ◽  
Hot Gas ◽  
Element Simulation ◽  
Mechanism Of Failure ◽  
The Relationship ◽  
Lubrication Conditions

Splitting at regions of local thinning below die entry radii is a critically important mechanism of failure in hot gas-pressure forming of sheet materials. Local thinning is controlled by sheet-die friction and die geometry, as well as sheet material properties. In this study, local thinning is investigated at a particularly severe die entry radius during hot forming of a fine-grained AA5083 sheet at 450°C. Particular emphasis is placed on the relationship between local thinning and sheet-die friction conditions. A simple analysis of the mechanics of this thinning phenomenon is presented. Finite element simulation results are presented for different sheet-die friction conditions. Sheet thickness profiles measured from parts produced in forming experiments using three different lubrication conditions are compared with predictions from simulations. Simulation predictions agree well with experimental data for the occurrence and location of thinning below a die entry radius. Additional insights into sheet-die friction for controlling local thinning and preventing premature necking failure are detailed.

scholarly journals Spring-like leg behaviour, musculoskeletal mechanics and control in maximum and submaximum height human hopping

2011 ◽  
Vol 366 (1570) ◽  
pp. 1516-1529 ◽  
Author(s):  
Maarten F. Bobbert ◽  
L. J. Richard Casius
Keyword(s):  
Energy Expenditure ◽  
Muscle Activation ◽  
Mechanical Energy ◽  
Reaction Force ◽  
Ground Reaction Forces ◽  
Centre Of Mass ◽  
Leg Stiffness ◽  
Reaction Forces ◽  
And Control ◽  
The Relationship

The purpose of this study was to understand how humans regulate their ‘leg stiffness’ in hopping, and to determine whether this regulation is intended to minimize energy expenditure. ‘Leg stiffness’ is the slope of the relationship between ground reaction force and displacement of the centre of mass (CM). Variations in leg stiffness were achieved in six subjects by having them hop at maximum and submaximum heights at a frequency of 1.7 Hz. Kinematics, ground reaction forces and electromyograms were measured. Leg stiffness decreased with hopping height, from 350 N m −1 kg −1 at 26 cm to 150 N m −1 kg −1 at 14 cm. Subjects reduced hopping height primarily by reducing the amplitude of muscle activation. Experimental results were reproduced with a model of the musculoskeletal system comprising four body segments and nine Hill-type muscles, with muscle stimulation STIM( t ) as only input. Correspondence between simulated hops and experimental hops was poor when STIM( t ) was optimized to minimize mechanical energy expenditure, but good when an objective function was used that penalized jerk of CM motion, suggesting that hopping subjects are not minimizing energy expenditure. Instead, we speculated, subjects are using a simple control strategy that results in smooth movements and a decrease in leg stiffness with hopping height.

scholarly journals Variability of the Relationship between Electrophysiology and BOLD-fMRI across Cortical Regions in Humans

2011 ◽  
Vol 31 (36) ◽  
pp. 12855-12865 ◽  
Author(s):  
C. R. Conner ◽  
T. M. Ellmore ◽  
T. A. Pieters ◽  
M. A. DiSano ◽  
N. Tandon
Keyword(s):  
Bold Fmri ◽  
Cortical Regions ◽  
The Relationship
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