scholarly journals Neural structure of a sensory decoder for motor control

2020 ◽  
Author(s):  
Seth W. Egger ◽  
Stephen G. Lisberger

ABSTRACTWe seek to understand the neural mechanisms that perform sensory decoding for motor behavior, advancing the field by designing decoders based on neural circuits. A simple experiment produced a surprising result that shapes our approach. Changing the size of a target for smooth pursuit eye movements changes the relationship between the variance and mean of the evoked behavior in a way that contradicts the regime of “signal-dependent noise” and defies traditional decoding approaches. A theoretical analysis leads us to conclude that sensory decoding circuits for pursuit include multiple parallel pathways and multiple sources of variation. Behavioral and neural responses with biomimetic statistics emerge from a biologically-motivated circuit model with noise in the pathway that is dedicated to flexibly adjusting the strength of visual-motor transmission. Flexible adjustment of transmission strength applies much more broadly to issues in sensory-motor control such as Bayesian integration and control strategies to optimize motor behavior.

Author(s):  
Nir Nesher ◽  
Guy Levy ◽  
Letizia Zullo ◽  
Benyamin Hochner

The octopus, with its eight long and flexible arms, is an excellent example of the independent evolution of highly efficient motor behavior in a soft-bodied animal. Studies will be summarized to show that the amazing behavioral motor abilities of the octopus are achieved through a special embodied organization of its flexible body, unusual morphology, and a unique central and peripheral distribution of its extremely large nervous system. This special embodied organization of brain–body–environment reciprocal interactions makes it possible to overcome the difficulties involved in generation and control of movement in an animal, which unlike vertebrates and arthropods lacks rigid skeletal appendages.


Author(s):  
Sedighe Karimzadeh ◽  
Raj Bhopal ◽  
Huy Nguyen Tien

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is pandemic. Prevention and control strategies require an improved understanding of SARS-CoV-2 dynamics. We did a rapid review of the literature on SARS-CoV-2 viral dynamics with a focus on infective dose. We sought comparisons of SARS-CoV-2 with other respiratory viruses including SARS-CoV-1 and MERS-CoV. We examined laboratory animal, and human studies. The literature on infective dose, transmission, and routes of exposure was limited specially in humans, and varying endpoints were used for measurement of infection. We propose the minimum infective dose of COVID-19 in humans, is higher than 100 particles, possibly slightly lower than the 700 particles estimated for H1N1 influenza. Despite variability in animal studies, there was some evidence that increased dose at exposure correlated with higher viral load clinically, and severer symptoms. Higher viral load measures did not reflect COVID-19 severity. Aerosol transmission seemed to raise the risk of more severe respiratory complications in animals. An accurate quantitative estimate of the infective dose of SARS-CoV-2 in humans is not currently feasible and needs further research. Further work is also required on the relationship between routes of transmission, infective dose, co-infection, and outcomes.


2015 ◽  
Vol 90 (4) ◽  
pp. 469-475 ◽  
Author(s):  
M.K. Bouyou Akotet ◽  
M. Owono-Medang ◽  
D.P. Mawili-Mboumba ◽  
M.N. Moussavou-Boussougou ◽  
S. Nzenze Afène ◽  
...  

AbstractThe relationship between the frequency of loiasis objective symptoms and microfilaraemic or amicrofilaraemic infection was assessed in 1148 exposed patients also infected, or not, with Mansonella perstans. Filarial infections were detected by direct microscopy, leucoconcentration and serology, with prevalence values of 39.5% Loa loa, 5.6% M. perstans and 3.4% co-infection with both filarial species. Amicrofilaraemic or occult loiasis (OL) predominated among L. loa-infected individuals, with a prevalence of 58.2%. Hypermicrofilaraemia (>8000 microfilariae (mf)/ml) was found in 18.4% of L. loa microfilaraemic patients, with 25.7% of them harbouring more than 30,000 mf/ml. Up to 34% of patients with OL showed evidence of Calabar swelling, compared with 26.3% of microfilaraemic patients (P= 0.03). Overall 5.3% of patients presented with adult worm migration across the eye, representing 16.3% of microfilaraemic individuals and 11.4% of amicrofilaraemic patients (P= 0.13). This symptom was similarly found in patients with more than 30,000 mf/ml (22%), those with microfilaraemia between 8 and 30,000 mf/ml (15.4%) and also in individuals with low or without microfilaraemia (16.1%) (P= 0.7). Five (14.3%) hypermicrofilaraemic patients did not present any L. loa-specific objective symptoms, as well as all the patients with single M. perstans infection. The presence of adult eye worm migration as a strong predictor of high microfilaraemia density would obscure the real burden of L. loa hypermicrofilaraemia in exposed individuals. For epidemiological purposes and control strategies, the mapping of L. loa in endemic areas should also take into account the group of patients with occult loiasis.


2012 ◽  
Vol 562-564 ◽  
pp. 1602-1605
Author(s):  
Cheng Qun Li ◽  
Cui Yu Zhou

Based on the relationship between the motor torque of each side and electric current when the electric vehicle turns, this article puts forward a control scheme of electronic differential which is used to regulate current and control torque, according to the micro electric vehicle with a double-wheel motor driven. In addition, the article makes detailed analysis for the electronic differential control process.


1996 ◽  
Vol 39 (3) ◽  
pp. 546-564 ◽  
Author(s):  
Pascal H. H. M. van Lieshout ◽  
Wouter Hulstijn ◽  
Herman F. M. Peters

The main purpose of the present study was to differentiate between people who stutter and control speakers regarding their ability to assemble motor plans and to prepare (and execute) muscle commands. Adult males who stutter, matched for age, gender, and educational level with a group of control speakers, were tested on naming words and symbols. In addition, their ability to encode and retrieve memory representations of combinations of a symbol and a word, was tested in a recognition task, using manual reaction times and sensitivity scores, as defined in signal detection theory, as performance measures. Group differences in muscle command preparation were assessed from electromyographic recordings of upper lip and lower lip. Results indicated no interaction between group and word size effects in choice reaction times or a group effect in the ability to recognize previously learned symbol-word combinations. However, they were significantly different in the timing of peak amplitudes in the integrated electromyographic signals of upper lip and lower lip (IEMG peak latency). Findings question the claim that people who stutter have problems in creating abstract motor plans for speech. In addition, it is argued that the group differences in IEMG peak latency that were found in the present study might be better understood in terms of motor control strategies than in terms of motor control deficits.


2017 ◽  
Author(s):  
Alun L. Lloyd ◽  
Uriel Kitron ◽  
T. Alex Perkins ◽  
Gonzalo M. Vazquez-Prokopec ◽  
Lance A. Waller

AbstractIn mathematical epidemiology, a well-known formula describes the impact of heterogeneity on the basic reproductive number, R0, for situations in which transmission is separable and for which there is one source of variation in susceptibility and one source of variation in infectiousness. This formula is written in terms of the magnitudes of the heterogeneities, as quantified by their coefficients of variation, and the correlation between them. A natural question to ask is whether analogous results apply when there are multiple sources of variation in susceptibility and/or infectiousness. In this paper we demonstrate that with three or more coupled heterogeneities, R0 under separable transmission depends on details of the distribution of the heterogeneities in a way that is not seen in the well-known simpler situation. We provide explicit formulae for the cases of multivariate normal and multivariate log-normal distributions, showing that R0 can again be expressed in terms of the magnitudes of the heterogeneities and the pairwise correlations between them. The formulae, however, differ between the two multivariate distributions, demonstrating that no formula of this type applies generally when there are three or more coupled heterogeneities. We see that the results of the formulae are approximately equal when heterogeneities are relatively small and show that an earlier result in the literature (Koella, 1991) should be viewed in this light. We provide numerical illustrations of our results and discuss a setting in which coupled heterogeneities are likely to have a major impact on the value of R0. We also describe a rather surprising result: in a system with three heterogeneities, R0 can exhibit non-monotonic behavior with increasing levels of heterogeneity, in marked contrast to the familiar two heterogeneity setting in which R0 either increases or decreases with increasing heterogeneity.


2015 ◽  
Author(s):  
Donna H. Krasnow ◽  
M. Virginia Wilmerding

As dance training evolves and becomes more complex, knowledge of motor behavior is foundational in helping dancers learn and master new skills and become more efficient in integrating the skills. Motor Learning and Control for Dance is the first resource to address motor learning theory from a dance perspective. Educators and students preparing to teach will learn practical ways to connect the science behind dance to pedagogy in order to prepare dancers for performance. Dancers interested in performance from the recreational to professional levels will learn ways to enhance their technical and artistic progress. In language accessible even to those with no science background, Motor Learning and Control for Dance showcases principles and practices for students, artists, and teachers. The text offers a perspective on movement education not found in traditional dance training while adding to a palette of tools and strategies for improving dance instruction and performance. Aspiring dancers and instructors will explore how to develop motor skills, how to control movement on all levels, and—most important—how motor skills are best taught and learned. The authors, noted experts on motor learning and motor control in the dance world, explore these features that appeal to students and instructors alike: • Dance-specific photos, examples, and figures illustrate how to solve common problems various dance genres. • The 16 chapters prepare dance educators to teach dancers of all ages and abilities and support the development of dance artists and students in training and performance. • An extensive bibliography of sports and dance science literature allows teachers and performers to do their own research. • A list of key terms is at the beginning of each chapter with an accompanying glossary at the back of the book. Part I presents an overview of motor behavior, covering motor development from birth to early adulthood. It provides the essential information for teaching posture control and balance, the locomotor skills underlying a range of complex dance skills, and the ballistic skills that are difficult to teach and learn, such as grand battement and movements in street dance. Part II explores motor control and how movement is planned, initiated, and executed. Readers will learn how the nervous system organizes the coordination of movement, the effects of anxiety and states of arousal on dance performance, how to integrate the senses into movement, and how speed and accuracy interact. Part III investigates methods of motor learning for dancers of all ages. Readers will explore how to implement a variety of instructional strategies, determine the best approaches for learning dance skills, and motivate and inspire dancers. This section also discusses how various methods of practice can help or hinder dancers, strategies for improving the recall of dance skills and sequences, and how to embrace somatic practice and its contribution to understanding imagery and motor learning. Motor Learning and Control for Dance addresses many related topics that are important to the discipline, such as imagery and improvisation. This book will help performers and teachers blend science with pedagogy to meet the challenge of artistry and technique in preparing for dance performaance.


2014 ◽  
Vol 3 (3) ◽  
pp. 280-291 ◽  
Author(s):  
Richard Moulding ◽  
Meredith E. Coles ◽  
Jonathan S. Abramowitz ◽  
Gillian M. Alcolado ◽  
Pino Alonso ◽  
...  

2021 ◽  
Author(s):  
Julien Vollering ◽  
Siri Lie Olsen ◽  
Olav Skarpaas ◽  
Leif Appelgren ◽  
Magni Olsen Kyrkjeeide ◽  
...  

1. Plantations of alien conifer species are common worldwide, and set to become even more prevalent in coming decades. To minimize the rate at which their offspring --- so-called "wildlings" --- colonize surroundings, and reduce the burden of conifer plantations on native ecosystems, managers need to know which ecosystems are most and least susceptible.2. We compared how likely wildlings are to establish across a wide range of ecosystems, focusing on four groups of alien conifer species planted in Norway. We used data from detailed surveys around 82 plantation stands to model the relationship between ecosystem type and wildling abundance, accounting for seed rain (estimated), climate, and other sources of variation between sites. We also tested whether differences in susceptibility between individual ecosystem types could be generalized based on broad, shared characteristics.3. We found that ecosystem susceptibility to wildling establishment (modeled as relative establishment likelihood) was poorly correlated with surveyed wildling density (abundance/area). Susceptibility generally varied as much or more than wildling density, with relative establishment likelihoods spanning several orders of magnitude between the most and least susceptible ecosystems for every species group.4. The four groups of conifer species showed somewhat similar patterns of establishment likelihood across ecosystem types, with intensively farmed ecosystems repeatedly among the least susceptible. We found that ecosystems characterized by destabilizing disturbance tended to be more susceptible than others, but broad ecosystem characteristics did not clarify patterns of susceptibility much, neither within nor across species groups. 5. *Synthesis and applications* Differences in wildling establishment between ecosystems can be exploited to keep alien conifers within plantation boundaries. Stands hemmed in by agriculture or other unsusceptible ecosystems will result in relatively few wildlings, while stands near susceptible ecosystems like landslides will need monitoring and control. Managers should be aware that the density of wildlings in a given ecosystem may not reflect its relative susceptibility, because variation in seed rain, climate, and site characteristics obscures the relationship between ecosystem type and wildling establishment.


Sign in / Sign up

Export Citation Format

Share Document