scholarly journals Shifts in Estimated Preferred Directions During Simulated BMI Experiments With No Adaptation

2021 ◽  
Vol 15 ◽  
Author(s):  
Miri Benyamini ◽  
Miriam Zacksenhouse
Keyword(s):  
Theoretical Analysis ◽  
Motor Neurons ◽  
Motor Units ◽  
Neural Adaptation ◽  
Experimental Conditions ◽  
Simulation Tools ◽  
Preferred Direction ◽  
Cortical Motor ◽  
Optimal State Estimation ◽  
And Control

Experiments with brain-machine interfaces (BMIs) reveal that the estimated preferred direction (EPD) of cortical motor units may shift following the transition to brain control. However, the cause of those shifts, and in particular, whether they imply neural adaptation, is an open issue. Here we address this question in simulations and theoretical analysis. Simulations are based on the assumption that the brain implements optimal state estimation and feedback control and that cortical motor neurons encode the estimated state and control vector. Our simulations successfully reproduce apparent shifts in EPDs observed in BMI experiments with different BMI filters, including linear, Kalman and re-calibrated Kalman filters, even with no neural adaptation. Theoretical analysis identifies the conditions for reducing those shifts. We demonstrate that simulations that better satisfy those conditions result in smaller shifts in EPDs. We conclude that the observed shifts in EPDs may result from experimental conditions, and in particular correlated velocities or tuning weights, even with no adaptation. Under the above assumptions, we show that if neurons are tuned differently to the estimated velocity, estimated position and control signal, the EPD with respect to actual velocity may not capture the real PD in which the neuron encodes the estimated velocity. Our investigation provides theoretical and simulation tools for better understanding shifts in EPD and BMI experiments.

scholarly journals Suitability of the Cyclic Voltammetry Measurements and DPPH• Spectrophotometric Assay to Determine the Antioxidant Capacity of Food-Grade Oenological Tannins

Molecules ◽  
2019 ◽  
Vol 24 (16) ◽  
pp. 2925 ◽  
Author(s):  
Arianna Ricci ◽  
Giuseppina Paola Parpinello ◽  
Nemanja Teslić ◽  
Paul Andrew Kilmartin ◽  
Andrea Versari
Keyword(s):  
Cyclic Voltammetry ◽  
Colorimetric Assay ◽  
Radical Scavenging ◽  
Calibration Graph ◽  
Spectrophotometric Assay ◽  
Experimental Conditions ◽  
Fast Analysis ◽  
Cv Measurements ◽  
And Control ◽  
Analytical Approaches

Twenty commercially available oenological tannins (including hydrolysable and condensed) were assessed for their antiradical/reducing activity, comparing two analytical approaches: The 2,2-diphenyl-1-picrylhydrazyl (DPPH•) radical scavenging spectrophotometric assay and the cyclic voltammetry (CV) electrochemical method. Electrochemical measurements were performed over a −200 mV–500 mV scan range, and integrated anodic currents to 500 mV were used to build a calibration graph with (+)-catechin as a reference standard (linear range: From 0.0078 to 1 mM, R2 = 0.9887). The CV results were compared with the DPPH• assay (expressed as % of radical scavenged in time), showing high correlation due to the similarity of the chemical mechanisms underlying both methods involving polyphenolic compounds as reductants. Improved correlation was observed by increasing the incubation time with DPPH• to 24 h (R2 = 0.925), demonstrating that the spectrophotometric method requires a long-term incubation to complete the scavenging reaction when high-molecular weight tannins are involved; this constraint has been overcome by using instant CV measurements. We concluded that the CV represents a valid alternative to the DPPH• colorimetric assay, taking advantage of fast analysis and control on the experimental conditions and, because of these properties, it can assist the quality control along the supply chain.

scholarly journals How Downward and Upward Comparisons on Facebook Influence Grandiose and Vulnerable Narcissists’ Self-Esteem—A Priming Study

2021 ◽  
Vol 11 (3) ◽  
pp. 39
Author(s):  
Phillip Ozimek ◽  
Hans-Werner Bierhoff ◽  
Elke Rohmann
Keyword(s):  
Social Networking Sites ◽  
Online Survey ◽  
Social Comparisons ◽  
Past Research ◽  
Self Esteem ◽  
Self Report ◽  
Control Group ◽  
Experimental Conditions ◽  
Vulnerable Narcissism ◽  
And Control

Past research showed that social networking sites represent perfect platforms to satisfy narcissistic needs. The present study aimed to investigate how grandiose (GN) and vulnerable narcissism (VN) as well as social comparisons are associated with Facebook activity, which was measured with a self-report on three activity dimensions: Acting, Impressing, and Watching. In addition, the state self-esteem (SSE) was measured with respect to performance, social behavior, and appearance. One hundred and ten participants completed an online survey containing measures of SSE and Facebook activity and a priming procedure with three experimental conditions embedded in a social media context (upward comparison, downward comparison, and control group). Results indicated, as expected, that high VN was negatively associated with SSE on each subscale and the overall score. In addition, it was found that VN, but not GN, displayed positive associations with frequency of Facebook activities. Finally, it was proposed and confirmed that VN in interaction with the priming of downward comparisons negatively affected SSE. The conclusion drawn is that VN represents a key variable for the prediction of self-esteem as well as for the frequency of Facebook activity.

scholarly journals Ultramicroscopy Reveals Axonal Transport Impairments in Cortical Motor Neurons at Prion Disease

2009 ◽  
Vol 96 (8) ◽  
pp. 3390-3398 ◽  
Author(s):  
Vladimir Ermolayev ◽  
Mike Friedrich ◽  
Revaz Nozadze ◽  
Toni Cathomen ◽  
Michael A. Klein ◽  
...  
Keyword(s):  
Axonal Transport ◽  
Prion Disease ◽  
Motor Neurons ◽  
Cortical Motor

scholarly journals A gradient field defeats the inherent repulsion between magnetic nanorods

2014 ◽  
Vol 1 (2) ◽  
pp. 140271 ◽  
Author(s):  
Yu Gu ◽  
Ruslan Burtovyy ◽  
John Custer ◽  
Igor Luzinov ◽  
Konstantin G. Kornev
Keyword(s):  
Phase Portrait ◽  
High Speed ◽  
Uniform Magnetic Field ◽  
Gradient Field ◽  
Physical Parameters ◽  
Uniform Field ◽  
Experimental Conditions ◽  
Magnetic Nanorods ◽  
Field Gradients ◽  
And Control

When controlling the assembly of magnetic nanorods and chains of magnetic nanoparticles, it is extremely challenging to bring them together side by side while keeping a desired spacing between their axes. We show that this challenge can be successfully resolved by using a non-uniform magnetic field that defeats an inherent repulsion between nanorods. Nickel nanorods were suspended in a viscous film and a non-uniform field was used to control their placement. The in-plane movement of nanorods was tracked with a high-speed camera and a detailed image analysis was conducted to quantitatively characterize the behaviour of the nanorods. The analysis focused on the behaviour of a pair of neighbour nanorods, and a corresponding dynamic model was formulated and investigated. The complex two-dimensional dynamics of a nanorod pair was analysed analytically and numerically, and a phase portrait was constructed. Using this phase portrait, we classified the nanorod behaviour and revealed the experimental conditions in which nanorods could be placed side by side. Dependence of the distance between a pair of neighbour nanorods on physical parameters was analysed. With the aid of the proposed theory, one can build different lattices and control their spacing by applying different field gradients.

scholarly journals Achieving equitable uptake of handwashing and sanitation by addressing both supply and demand-based constraints: findings from a randomized controlled trial in rural Bangladesh

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Sarker Masud Parvez ◽  
Musarrat Jabeen Rahman ◽  
Rashidul Azad ◽  
Mahbubur Rahman ◽  
Leanne Unicomb ◽  
...  
Keyword(s):  
Controlled Trial ◽  
Supply And Demand ◽  
Efficacy Trial ◽  
Experimental Conditions ◽  
Randomized Controlled ◽  
Link Type ◽  
Education Levels ◽  
Change Promotion ◽  
And Control ◽  
The Impact

Abstract Background Supply driven programs that are not closely connected to community demand and demand-driven programs that fail to ensure supply both risk worsening inequity. Understanding patterns of uptake of behaviors among the poorest under ideal experimental conditions, such as those of an efficacy trial, can help identify strategies that could be strengthened in routine programmatic conditions for more equitable uptake. WASH Benefits Bangladesh was a randomized controlled efficacy trial that provided free-of cost WASH hardware along with behavior change promotion. The current paper aimed to determine the impact of the removal of supply and demand constraints on the uptake of handwashing and sanitation behaviors across wealth and education levels. Methods The current analysis selected 4 indicators from the WASH Benefits trial— presence of water and soap in household handwashing stations, observed mother’s hand cleanliness, observed visible feces on latrine slab or floor and reported last child defecation in potty or toilet. A baseline assessment was conducted immediately after enrolment and endline assessment was conducted approximately 2 years later. We compared change in uptake of these indicators including wealth quintiles (Q) between intervention and control groups from baseline to endline. Results For hand cleanliness, the poorest mothers improved more [Q1 difference in difference, DID: 16% (7, 25%)] than the wealthiest mothers [Q5 DID: 7% (− 4, 17%)]. The poorest households had largest improvements for observed presence of water and soap in handwashing station [Q1 DID: 82% (75, 90%)] compared to the wealthiest households [Q5 DID: 39% (30, 50%)]. Similarly, poorer household demonstrated greater reductions in visible feces on latrine slab or floor [Q1DID, − 25% (− 35, − 15) Q2: − 34% (− 44, − 23%)] than the wealthiest household [Q5 DID: − 1% (− 11, 8%). For reported last child defecation in potty or toilet, the poorest mothers showed greater improvement [Q1–4 DID: 50–54% (44, 60%)] than the wealthier mothers [Q5 DID: 39% (31, 46%). Conclusion By simultaneously addressing supply and demand-constraints among the poorest, we observed substantial overall improvements in equity. Within scaled-up programs, a separate targeted strategy that relaxes constraints for the poorest can improve the equity of a program. Trial registration WASH Benefits Bangladesh: ClinicalTrials.gov, identifier: NCT01590095. Date of registration: April 30, 2012 ‘Retrospectively registered’.

Motor Patterns During Flight and Warm-up in Lepidoptera

1968 ◽  
Vol 48 (1) ◽  
pp. 89-109
Author(s):  
ANN E. KAMMER
Keyword(s):  
Motor Neurons ◽  
Muscle Activity ◽  
Motor Units ◽  
Wingbeat Frequency ◽  
Motor Patterns ◽  
Flight Pattern ◽  
Warm Up ◽  
Burst Length ◽  
Synergistic Muscles ◽  
Phase Relationships

1. The patterns of muscle activity during warm-up were compared to those of flight. In the skipper Hylephila phylaeus and in the hawk moths Celerio lineata and Mimas tiliae the intervals between bursts of muscle potentials are the same as the wingbeat periods of flight at the same thoracic temperature, and the burst length is the same as in flight. In saturniids the period and burst length are both shorter during wing-vibrating than during flight. 2. During wing-vibrating the amplitude of the wing movement is small, and some of the muscles which are antagonists in flight are active simultaneously. In Hylephila phylaeus and Celerio lineata there is a phase change between some synergistic muscles, while some antagonistic pairs retain the phase relationships of flight. During wing-vibrating in Mimas tiliae and in saturniids all the motor units sampled were active at the same time. 3. In M. tiliae a variety of phase relationships intermediate between those of wing-vibrating and flight were observed, including a case of ‘relative co-ordination’ between motor units in the mesothorax. The results exclude the possibility that a single pace-making centre drives the motor neurons in the flight pattern. 4. A model of the central nervous interactions which generate the observed motor patterns is proposed. It is postulated that a small group of positively coupled neurons produces bursts of impulses at the wingbeat frequency and that these groups interact to generate the phase relationships seen during warm-up and flight.

scholarly journals Statistical assessment of the stability of neural movement representations

2011 ◽  
Vol 106 (2) ◽  
pp. 764-774 ◽  
Author(s):  
Ian H. Stevenson ◽  
Anil Cherian ◽  
Brian M. London ◽  
Nicholas A. Sachs ◽  
Eric Lindberg ◽  
...  
Keyword(s):  
Primary Motor Cortex ◽  
Tuning Curve ◽  
Modulation Depth ◽  
Measurement Noise ◽  
Neural Representation ◽  
Experimental Conditions ◽  
Sensory Stimuli ◽  
Tuning Curves ◽  
Dynamic Tuning ◽  
Preferred Direction

In systems neuroscience, neural activity that represents movements or sensory stimuli is often characterized by spatial tuning curves that may change in response to training, attention, altered mechanics, or the passage of time. A vital step in determining whether tuning curves change is accounting for estimation uncertainty due to measurement noise. In this study, we address the issue of tuning curve stability using methods that take uncertainty directly into account. We analyze data recorded from neurons in primary motor cortex using chronically implanted, multielectrode arrays in four monkeys performing center-out reaching. With the use of simulations, we demonstrate that under typical experimental conditions, the effect of neuronal noise on estimated preferred direction can be quite large and is affected by both the amount of data and the modulation depth of the neurons. In experimental data, we find that after taking uncertainty into account using bootstrapping techniques, the majority of neurons appears to be very stable on a timescale of minutes to hours. Lastly, we introduce adaptive filtering methods to explicitly model dynamic tuning curves. In contrast to several previous findings suggesting that tuning curves may be in constant flux, we conclude that the neural representation of limb movement is, on average, quite stable and that impressions to the contrary may be largely the result of measurement noise.

The Design and Research of Virtualization Platform

2013 ◽  
Vol 397-400 ◽  
pp. 2090-2093
Author(s):  
An Hong Tian ◽  
Cheng Biao Fu
Keyword(s):  
Theoretical Analysis ◽  
Network Structure ◽  
Computer Network ◽  
Local Area Network ◽  
Local Area ◽  
Virtual Simulation ◽  
Area Network ◽  
Simulation Tools ◽  
Detail Design ◽  
Packet Tracer

Due to the problem of network structure, security, redundant path in traditional network, this can be solved by Virtual Local Area Network (VLAN) technology. As the network laboratory in colleges and universities is not perfect because of high cost, a virtual simulation tools named Packet Tracer has been introduced to computer network experimental curriculum, this paper put forwards the detail design scheme by the example of VLAN with three switches, and provides the experiment and theoretical analysis and simulation verification .The practice has proved this method not only deepens students comprehension of network, but also cultivates the students' actual comprehensive ability.

scholarly journals In vitro activity of zinc oxide-eugenol and glass ionomer cements on Candida albicans

2005 ◽  
Vol 19 (2) ◽  
pp. 134-138 ◽  
Author(s):  
Anna Carolina Aguiar Cassanho ◽  
Aletéia Massula Fernandes ◽  
Luciane Dias de Oliveira ◽  
Claudio Antonio Talge Carvalho ◽  
Antonio Olavo Cardoso Jorge ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Candida Albicans ◽  
Control Group ◽  
Glass Ionomer ◽  
Experimental Conditions ◽  
Mean Values ◽  
Zinc Oxide Eugenol ◽  
Colony Forming Units ◽  
And Control

The aim of this study was to evaluate in vitro the antimicrobial activity of glass ionomer (GIC) and zinc oxide-eugenol (ZOE) cements against Candida albicans. Standardized GIC and ZOE specimens were maintained in contact with C. albicans suspension (1 <FONT FACE=Symbol>´</FONT> 10(6) cells/ml) at 37°C for 24 h, 48 h or 7 days. A control group without any testing cement was included. After the incubation period, aliquots of 0.1 ml were plated on Sabouraud's agar, and then the number of colonies was counted. The results were expressed as values of logarithms of colony-forming units per milliliter (log CFU/mL) and were analyzed statistically by Kruskal-Wallis ANOVA. After 48 h of incubation, the ZOE group presented no growth of C. albicans. GIC and control groups presented similar mean values at all tested periods. According to the results obtained, it could be concluded that, under the experimental conditions, ZOE cement was more effective in vitro against C. albicans than GIC.

Neuronal mechanisms underlying physiological tremor

1978 ◽  
Vol 41 (3) ◽  
pp. 557-571 ◽  
Author(s):  
J. H. Allum ◽  
V. Dietz ◽  
H. J. Freund
Keyword(s):  
Power Spectrum ◽  
Pathological Condition ◽  
Power Spectra ◽  
Motor Units ◽  
Physiological Tremor ◽  
Force Level ◽  
Force Output ◽  
Experimental Conditions ◽  
Single Motor Unit ◽  
Total Fusion

1. Tremor force was recorded during stationary isometric contractions of intrinsic hand muscles of normal subjects. Subjects maintained a steady force level between their thumb and forefinger for 30 s. The force level varied from weak (0.2 kg) to strong contractions (7 kg). These experimental conditions were the same as those in two preceding studies, where single motor-unit activity (14) and the correlation between the discharges of two simultaneously recorded motor units and physiological tremor (11) have been investigated. 2. Two alterations of the power spectra were observed at successively stronger contractions: increase of tremor amplitude and changes in the shape of the power spectrum. At all force levels, the power spectra of tremor force show the well-known decay of tremor amplitude from the lower to the higher frequencies with a local peak at 6--10 Hz. This peak does not show a significant change with respect to frequency when the force level is varied. It is shifted toward lower frequencies in a pathological condition (Parkinsonism) where the recruitment firing rates of the motor units are significantly lower than in the normal. 3. Higher frequencies (greater than 20 Hz) are barely present in the power spectrum during the very weak contractions. They become significant as the contractions become stronger. 4. The steep decay of the power spectrum toward higher frequencies has a similar slope (--43 dB/decade) as the reduction in amplitude of the unfused part of the muscle contractions with increasing stimulus rates (--38 dB/decade). The cutoff of the power spectrum above 25 Hz parallels the achievement of total fusion of muscle twitches above this rate. 5. The results are consistent with the hypothesis that the power spectrum over the range of 6--25 Hz is mainly caused by the unfused parts of the twitch contractions of motor units firing between recruitment (6--8/s) and total fusion of the twitches (25--30/s). The decline of the power spectrum toward higher frequencies can be explained by mechanical damping, which results from increasing fusion of the twitch contractions. The low-frequency part of the power spectrum is assumed to be the result of the slow force deviations produced by changes in the net output of the motoneuron pool. 6. These assumptions were supported by additional animal experiments where the number and rate of force-producing elements could be controlled. Bundles of ventral root filaments innervating cat soleus and gastrocnemius muscles were stimulated synchronously and asynchronously at a number of different rates. The force output of the strain gauge was recorded, filtered, and analyzed in the same way as the human force records. 7. Stimualtion of one nerve bundle at one fixed frequency led to a sharp peak in the power spectrum at that frequency plus peaks of decreasing height representing the harmonics of the stimulation frequency. The height of the peaks decreased at --37 dB/decade. 8...

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