scholarly journals Individual differences in the neural strategies to control the lateral and medial head of the quadriceps during a mechanically constrained task

2020 ◽  
Author(s):  
Simon Avrillon ◽  
Alessandro Del Vecchio ◽  
Dario Farina ◽  
José L. Pons ◽  
Clément Vogel ◽  
...  
Keyword(s):  
Individual Differences ◽  
Motor Neurons ◽  
Interindividual Variability ◽  
Vastus Lateralis ◽  
Motor Units ◽  
Peak Torque ◽  
Motor Tasks ◽  
Neural Drive ◽  
Density Surface ◽  
The Individual

The interindividual variability in the neural drive sent from the spinal cord to muscles is largely unknown, even during highly constrained motor tasks. Here, we investigated individual differences in the strength of neural drive received by the vastus lateralis (VL) and vastus medialis (VM) during an isometric task. We also assessed the proportion of common neural drive within and between these muscles. Twenty-two participants performed a series of submaximal isometric knee extensions at 25% of their peak torque. High-density surface electromyography recordings were decomposed into motor unit action potentials. Coherence analyses were applied on the motor units spike trains to assess the degree of neural drive that was shared between motor neurons. Six participants were re-tested approximately 20 months after the first session. The distribution of the strength of neural drive between VL and VM varied between participants and was correlated with the distribution of normalized interference EMG (r > 0.56). The level of within and between muscle coherence varied across individuals, with a significant positive correlation between these two outcomes (VL: r=0.48; VM: r=0.58). We also observed a large interindividual variability in the proportion of muscle-specific drive, i.e. the drive unique to each muscle (VL range: 6-83%, VM range:6-86%). All the outcome measures were robust across sessions, providing evidence that the individual differences did not depend solely on the variability of the measures. Together, these results demonstrate that the neural strategies to control the VL and VM muscles widely vary across individuals, even during a constrained task.

scholarly journals Influence of common synaptic input to motor neurons on the neural drive to muscle in essential tremor

2015 ◽  
Vol 113 (1) ◽  
pp. 182-191 ◽  
Author(s):  
Juan A. Gallego ◽  
Jakob L. Dideriksen ◽  
Ales Holobar ◽  
Jaime Ibáñez ◽  
José L. Pons ◽  
...  
Keyword(s):  
Motor Unit ◽  
Motor Neurons ◽  
Synaptic Input ◽  
Motor Units ◽  
Spike Trains ◽  
Neural Drive ◽  
Systematic Analysis ◽  
Synaptic Inputs ◽  
Tremor Frequency ◽  
Unit Spike

Tremor in essential tremor (ET) is generated by pathological oscillations at 4–12 Hz, likely originating at cerebello-thalamo-cortical pathways. However, the way in which tremor is represented in the output of the spinal cord circuitries is largely unknown because of the difficulties in identifying the behavior of individual motor units from tremulous muscles. By using novel methods for the decomposition of multichannel surface EMG, we provide a systematic analysis of the discharge properties of motor units in nine ET patients, with concurrent recordings of EEG activity. This analysis allowed us to infer the contribution of common synaptic inputs to motor neurons in ET. Motor unit short-term synchronization was significantly greater in ET patients than in healthy subjects. Furthermore, the strong association between the degree of synchronization and the peak in coherence between motor unit spike trains at the tremor frequency indicated that the high synchronization levels were generated mainly by common synaptic inputs specifically at the tremor frequency. The coherence between EEG and motor unit spike trains demonstrated the presence of common cortical input to the motor neurons at the tremor frequency. Nonetheless, the strength of this input was uncorrelated to the net common synaptic input at the tremor frequency, suggesting a contribution of spinal afferents or secondary supraspinal pathways in projecting common input at the tremor frequency. These results provide the first systematic analysis of the neural drive to the muscle in ET and elucidate some of its characteristics that determine pathological tremulous muscle activity.

Discharge Variability of Motor Units in an Intrinsic Muscle of Transplanted Hand

2008 ◽  
Vol 99 (5) ◽  
pp. 2232-2240 ◽  
Author(s):  
Dario Farina ◽  
Marco Pozzo ◽  
Marco Lanzetta ◽  
Roger M. Enoka
Keyword(s):  
Motor Neurons ◽  
Action Potentials ◽  
Discharge Rate ◽  
Motor Units ◽  
Surface Emg ◽  
Intrinsic Muscle ◽  
Single Motor Units ◽  
Abductor Digiti Minimi ◽  
The Individual ◽  
Ramp Contractions

The study analyzed the discharge characteristics of the motor units in an intrinsic muscle of a transplanted hand. Multichannel electromyographic (EMG) recordings were obtained in 11 experimental sessions over 16 mo starting from day 205 after a hand was transplanted in a 35-yr-old man who had lost his right hand 22 yr earlier. The action potentials discharged by single motor units were identified from the surface EMG signals of the abductor digiti minimi muscle in the transplanted hand as the individual performed 60-s maximal and linearly increasing (ramp) contractions. Discharge rate decreased from 27.1 ± 8.4 pulses per second (pps) at the start of the maximal contractions to 17.2 ± 2.9 pps at the end ( P < 0.001) and increased from 17.4 ± 4.3 to 22.1 ± 5.0 pps during the ramp contractions ( P < 0.05). The SD of the interspike interval (ISI) nearly related to the mean ISI with a similar regression slope for the maximal (0.49 ± 0.09) and ramp contractions (0.43 ± 0.10). The coefficient of variation for ISI was higher than values in able-bodied persons and did not change during either the maximal (36.8 ± 10.8%) or the ramp contractions (35.9 ± 7.4%). High-frequency bursts of activity with <20 ms between two and six action potentials occurred during both maximal and ramp contractions. In conclusion, motor neurons that reinnervated a muscle in a transplanted hand discharged action potentials with a high degree of variability that suggested greater synaptic noise during the voluntary contractions.

scholarly journals Muscles from the same muscle group do not necessarily share common drive: evidence from the human triceps surae

2020 ◽  
Author(s):  
François Hug ◽  
Alessandro Del Vecchio ◽  
Simon Avrillon ◽  
Dario Farina ◽  
Kylie J. Tucker
Keyword(s):  
Motor Units ◽  
Muscle Group ◽  
Triceps Surae ◽  
Neural Drive ◽  
Flexible Control ◽  
Neural Origin ◽  
Density Surface ◽  
Motor Unit Action ◽  
Common Drive ◽  
Human Participants

It has been proposed that movements are produced through groups of muscles, or motor modules, activated by common neural commands. However, the neural origin of motor modules is still debated. Here, we used complementary approaches to determine: i) whether three muscles of the same muscle group (soleus, gastrocnemius medialis [GM] and lateralis [GL]) are activated by a common neural drive ; and ii) whether the neural drive to GM and GL could be differentially modified by altering the mechanical requirements of the task. Eighteen human participants performed an isometric standing heel raise and submaximal isometric plantarflexions (10%, 30%, 50% of maximal effort). High-density surface electromyography recordings were decomposed into motor unit action potentials and coherence analysis was applied on the motor units spike trains. We identified strong common drive to each muscle, but minimal common drive between the muscles. Further, large between-muscle differences were observed during the isometric plantarflexions, such as a delayed recruitment time of GL compared to GM and soleus motor units and opposite time-dependent changes in the estimates of neural drive to muscles during the torque plateau. Finally, the feet position adopted during the heel raise task (neutral vs internally rotated) affected only the GL neural drive with no change for GM. These results provide conclusive that not all anatomically defined synergist muscles are controlled by strong common neural drive. Independent drive to some muscles from the same muscle group may allow for more flexible control to comply with secondary goals such as joint stabilization.

Less common synaptic input between muscles from the same group allows for more flexible coordination strategies during a fatiguing task

2022 ◽  
Author(s):  
Julien Rossato ◽  
Kylie J. Tucker ◽  
Simon Avrillon ◽  
Lilian Lacourpaille ◽  
Ales Holobar ◽  
...  
Keyword(s):  
Synaptic Input ◽  
Vastus Lateralis ◽  
Rectus Femoris ◽  
Motor Units ◽  
The Other ◽  
Triceps Surae ◽  
Strong Positive Correlation ◽  
Neural Drive ◽  
Coordination Strategies ◽  
Common Drive

This study aimed to determine whether neural drive is redistributed between muscles during a fatiguing isometric contraction, and if so, whether the initial level of common synaptic input between these muscles constrains this redistribution. We studied two muscle groups: triceps surae (14 participants) and quadriceps (15 participants). Participants performed a series of submaximal isometric contractions and a torque-matched contraction maintained until task failure. We used high-density surface electromyography to identify the behavior of 1874 motor units from the soleus, gastrocnemius medialis (GM), gastrocnemius lateralis(GL), rectus femoris, vastus lateralis (VL), and vastus medialis(VM). We assessed the level of common drive between muscles in absence of fatigue using a coherence analysis. We also assessed the redistribution of neural drive between muscles during the fatiguing contraction through the correlation between their cumulative spike trains (index of neural drive). The level of common drive between VL and VM was significantly higher than that observed for the other muscle pairs, including GL-GM. The level of common drive increased during the fatiguing contraction, but the differences between muscle pairs persisted. We also observed a strong positive correlation of neural drive between VL and VM during the fatiguing contraction (r=0.82). This was not observed for the other muscle pairs, including GL-GM, which exhibited differential changes in neural drive. These results suggest that less common synaptic input between muscles allows for more flexible coordination strategies during a fatiguing task, i.e., differential changes in neural drive across muscles. The role of this flexibility on performance remains to be elucidated.

Individual Uniqueness in the Neonatal Functional Connectome

2021 ◽  
Author(s):  
Qiushi Wang ◽  
Yuehua Xu ◽  
Tengda Zhao ◽  
Zhilei Xu ◽  
Yong He ◽  
...  
Keyword(s):  
Individual Differences ◽  
Individual Identification ◽  
Imaging Data ◽  
Functional Connectome ◽  
Middle Range ◽  
Human Connectome Project ◽  
The Individual ◽  
And Behavior ◽  
Identification Analysis ◽  
The Brain

Abstract The functional connectome is highly distinctive in adults and adolescents, underlying individual differences in cognition and behavior. However, it remains unknown whether the individual uniqueness of the functional connectome is present in neonates, who are far from mature. Here, we utilized the multiband resting-state functional magnetic resonance imaging data of 40 healthy neonates from the Developing Human Connectome Project and a split-half analysis approach to characterize the uniqueness of the functional connectome in the neonatal brain. Through functional connectome-based individual identification analysis, we found that all the neonates were correctly identified, with the most discriminative regions predominantly confined to the higher-order cortices (e.g., prefrontal and parietal regions). The connectivities with the highest contributions to individual uniqueness were primarily located between different functional systems, and the short- (0–30 mm) and middle-range (30–60 mm) connectivities were more distinctive than the long-range (&gt;60 mm) connectivities. Interestingly, we found that functional data with a scanning length longer than 3.5 min were able to capture the individual uniqueness in the functional connectome. Our results highlight that individual uniqueness is present in the functional connectome of neonates and provide insights into the brain mechanisms underlying individual differences in cognition and behavior later in life.

Predictors of Positive Psychological Capital: An Attempt Among the Teacher Communities in Rural Jharkhand, India

2021 ◽  
pp. 0258042X2199101
Author(s):  
Mukti Clarence ◽  
Viju P. D. ◽  
Lalatendu Kesari Jena ◽  
Tony Sam George
Keyword(s):  
Individual Differences ◽  
Organizational Support ◽  
Psychological Capital ◽  
Contextual Factors ◽  
Meaningful Work ◽  
Equation Modeling ◽  
School Teachers ◽  
Positive Psychological Capital ◽  
The Individual ◽  
The Impact

In the recent times, researchers have shown an increased interest in positive psychological capital (PsyCap). However, it is acknowledged that due to the limited number of studies conducted on the antecedents of psychological capital, there is a lack of sufficient data for conclusively proving the antecedents of PsyCap. Consequently, this article aims to explore the potential antecedents of PsyCap as a reliable source of data in the context of rural school teachers. The focus is to investigate both the individual differences and the contextual factors as desirable variables that constitute PsyCap among the school teachers of rural Jharkhand, India. Samples of 1,120 respondents from different rural schools were collected and analysed with Structural Equation Modeling (AMOS 20.0). The findings of the study explained that both the individual differences ( proactive personality and emotional intelligence) and the contextual factors ( perceived organizational support, servant leadership and meaningful work) have a positive relationship with PsyCap. The impact of PsyCap on teacher performance can form the basis for further research on the subject. JEL Codes: M12, M53

scholarly journals Individual Differences in the Vocal Communication of Malayan Tapirs (Tapirus indicus) Considering Familiarity and Relatedness

Animals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 1026
Author(s):  
Robin Walb ◽  
Lorenzo von Fersen ◽  
Theo Meijer ◽  
Kurt Hammerschmidt
Keyword(s):  
Individual Differences ◽  
Vocal Communication ◽  
Social Role ◽  
Animal Communication ◽  
Solitary Living ◽  
Low Visibility ◽  
Living Species ◽  
The Individual ◽  
Tapirus Indicus

Studies in animal communication have shown that many species have individual distinct calls. These individual distinct vocalizations can play an important role in animal communication because they can carry important information about the age, sex, personality, or social role of the signaler. Although we have good knowledge regarding the importance of individual vocalization in social living mammals, it is less clear to what extent solitary living mammals possess individual distinct vocalizations. We recorded and analyzed the vocalizations of 14 captive adult Malayan tapirs (Tapirus indicus) (six females and eight males) to answer this question. We investigated whether familiarity or relatedness had an influence on call similarity. In addition to sex-related differences, we found significant differences between all subjects, comparable to the individual differences found in highly social living species. Surprisingly, kinship appeared to have no influence on call similarity, whereas familiar subjects exhibited significantly higher similarity in their harmonic calls compared to unfamiliar or related subjects. The results support the view that solitary animals could have individual distinct calls, like highly social animals. Therefore, it is likely that non-social factors, like low visibility, could have an influence on call individuality. The increasing knowledge of their behavior will help to protect this endangered species.

Control of cell shape by calcium in the euglenophyceae

1981 ◽  
Vol 49 (1) ◽  
pp. 99-117 ◽  
Author(s):  
J.M. Murray
Keyword(s):  
Endoplasmic Reticulum ◽  
Atpase Activity ◽  
Calcium Oxalate ◽  
Cell Shape ◽  
Motor Units ◽  
Astasia Longa ◽  
Oxalate Precipitation ◽  
Entire Cell ◽  
The Individual ◽  
Euglenoid Movement

The euglenoid flagellates are able to change their shape rapidly in response to a variety of stimuli, or sometimes spontaneously. Two extremes of shape can be identified: the “relaxed” form is cylindrical; the contracted form is a somewhat distorted disc. These 2 forms can be interconverted by treatments that alter the Ca2+ concentration of the entire cell. The level of Ca2+ is believed to be normally controlled by a system of calcium-accumulating membranes, identified in Astasia longa by the technique of calcium oxalate precipitation. The system forms a set of parallel tubes of endoplasmic reticulum, one of which lies immediately below each of the ridges of the pellicle. The individual ridges, each with its associated reticulum, microtubules and other elements are suggested to be independent motor units. Local activation of a small number of these units by Ca2+ is made possible by the arrangement of Ca2+ -sequestering reticulum, producing the characteristic squirming euglenoid movement. Uniform activation or suppression of all units produces the 2 extremes of shape. The pellicle of A. longa with its associated microtubules has been purified and shown to contain a Ca2+ -binding site and ATPase activity.

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.

Dynamic roles of social presence and individual differences in social TV platforms

2021 ◽  
pp. 135485652110575
Author(s):  
Jihyun Kim ◽  
Kelly Merrill
Keyword(s):  
Individual Differences ◽  
Social Presence ◽  
Online Survey ◽  
Unique Form ◽  
Tv Viewing ◽  
Television Content ◽  
Social Tv ◽  
The Social ◽  
Private And Public ◽  
The Individual

These days, many individuals engage in a unique form of TV viewing that includes a simultaneous act of watching television content and talking about it with others in a mediated environment. This phenomenon is commonly referred to as social TV viewing. Responding to the popularity of this form of TV viewing behavior, the present study examines the individual differences of the social TV viewing experience, particularly with regard to different communication platforms (e.g. private vs. public). Based on the data collected from an online survey, primary findings indicate that extroverted and lonely individuals have different social TV viewing experiences such as preferences for a particular type of platforms for social TV viewing. Further, social presence plays an important role in the understanding of social TV enjoyment in private and public platforms.

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