scholarly journals Fractionation of muscle activity in rapid responses to startling cues

2017 ◽  
Vol 117 (4) ◽  
pp. 1713-1719 ◽  
Author(s):  
Lauren R. Dean ◽  
Stuart N. Baker
Keyword(s):  
Muscle Activity ◽  
Human Subjects ◽  
Activity Patterns ◽  
Reaction Times ◽  
Principal Component ◽  
Similar Proportion ◽  
Descending Pathways ◽  
Healthy Human ◽  
Wide Range ◽  
The Right

Movements in response to acoustically startling cues have shorter reaction times than those following less intense sounds; this is known as the StartReact effect. The neural underpinnings for StartReact are unclear. One possibility is that startling cues preferentially invoke the reticulospinal tract to convey motor commands to spinal motoneurons. Reticulospinal outputs are highly divergent, controlling large groups of muscles in synergistic patterns. By contrast the dominant pathway in primate voluntary movement is the corticospinal tract, which can access small groups of muscles selectively. We therefore hypothesized that StartReact responses would be less fractionated than standard voluntary reactions. Electromyogram recordings were made from 15 muscles in 10 healthy human subjects as they carried out 32 varied movements with the right forelimb in response to startling and nonstartling auditory cues. Movements were chosen to elicit a wide range of muscle activations. Multidimensional muscle activity patterns were calculated at delays from 0 to 100 ms after the onset of muscle activity and subjected to principal component analysis to assess fractionation. In all cases, a similar proportion of the total variance could be explained by a reduced number of principal components for the startling and the nonstartling cue. Muscle activity patterns for a given task were very similar in response to startling and nonstartling cues. This suggests that movements produced in the StartReact paradigm rely on similar contributions from different descending pathways as those following voluntary responses to nonstartling cues. NEW & NOTEWORTHY We demonstrate that the ability to activate muscles selectively is preserved during the very rapid reactions produced following a startling cue. This suggests that the contributions from different descending pathways are comparable between these rapid reactions and more typical voluntary movements.

It is better an approximate answer to the right question than the exact answer to the wrong question : the case of the psychometric analysis of the ASQ:SE

2020 ◽  
Author(s):  
Luis Anunciacao ◽  
janet squires ◽  
J. Landeira-Fernandez
Keyword(s):  
Internal Structure ◽  
Statistical Methods ◽  
Principal Component ◽  
Psychological Theory ◽  
Published Data ◽  
Multivariate Statistical ◽  
Exact Answer ◽  
Wide Range ◽  
Ages And Stages Questionnaire ◽  
The Right

One of the main activities in psychometrics is to analyze the internal structure of a test. Multivariate statistical methods, including Exploratory Factor analysis (EFA) and Principal Component Analysis (PCA) are frequently used to do this, but the growth of Network Analysis (NA) places this method as a promising candidate. The results obtained by these methods are of valuable interest, as they not only produce evidence to explore if the test is measuring its intended construct, but also to deal with the substantive theory that motivated the test development. However, these different statistical methods come up with different answers, providing the basis for different analytical and theoretical strategies when one needs to choose a solution. In this study, we took advantage of a large volume of published data (n = 22,331) obtained by the Ages and Stages Questionnaire Social-Emotional (ASQ:SE), and formed a subset of 500 children to present and discuss alternative psychometric solutions to its internal structure, and also to its subjacent theory. The analyses were based on a polychoric matrix, the number of factors to retain followed several well-known rules of thumb, and a wide range of exploratory methods was fitted to the data, including EFA, PCA, and NA. The statistical outcomes were divergent, varying from 1 to 6 domains, allowing a flexible interpretation of the results. We argue that the use of statistical methods in the absence of a well-grounded psychological theory has limited applications, despite its appeal. All data and codes are available at https://osf.io/z6gwv/.

The C-start escape response ofPolypterus senegalus: bilateral muscle activity and variation during stage 1 and 2

2002 ◽  
Vol 205 (17) ◽  
pp. 2591-2603 ◽  
Author(s):  
Eric D. Tytell ◽  
George V. Lauder
Keyword(s):  
Muscle Activity ◽  
Escape Response ◽  
High Speed ◽  
Wave Speed ◽  
Activity Patterns ◽  
Motor Pattern ◽  
The Body ◽  
Wide Range ◽  
Fast Start ◽  
Stage 1

SUMMARYThe fast-start escape response is the primary reflexive escape mechanism in a wide phylogenetic range of fishes. To add detail to previously reported novel muscle activity patterns during the escape response of the bichir, Polypterus, we analyzed escape kinematics and muscle activity patterns in Polypterus senegalus using high-speed video and electromyography (EMG). Five fish were filmed at 250 Hz while synchronously recording white muscle activity at five sites on both sides of the body simultaneously (10 sites in total). Body wave speed and center of mass velocity, acceleration and curvature were calculated from digitized outlines. Six EMG variables per channel were also measured to characterize the motor pattern. P. senegalus shows a wide range of activity patterns, from very strong responses, in which the head often touched the tail, to very weak responses. This variation in strength is significantly correlated with the stimulus and is mechanically driven by changes in stage 1 muscle activity duration. Besides these changes in duration, the stage 1 muscle activity is unusual because it has strong bilateral activity, although the observed contralateral activity is significantly weaker and shorter in duration than ipsilateral activity. Bilateral activity may stiffen the body, but it does so by a constant amount over the variation we observed; therefore, P. senegalus does not modulate fast-start wave speed by changing body stiffness. Escape responses almost always have stage 2 contralateral muscle activity, often only in the anterior third of the body. The magnitude of the stage 2 activity is the primary predictor of final escape velocity.

Theory of Visual Attention (TVA)

2014 ◽  
Author(s):  
Claus Bundesen ◽  
Thomas Habekost
Keyword(s):  
Visual Attention ◽  
Single Cell ◽  
Human Subjects ◽  
Genetic Research ◽  
Reaction Times ◽  
Error Rates ◽  
Healthy Human ◽  
Computational Theory ◽  
Healthy Human Subjects ◽  
Psychological Studies

The theory of visual attention introduced by Bundesen (1990) is reviewed. The authors first describe TVA as a formal computational theory of visual attention and summarize applications of TVA to psychological studies of performance (reaction times and error rates) in healthy human subjects. They then explain their neurophysiological interpretation of TVA, NTVA, and exemplify how NTVA accounts for findings from single-cell studies in primates. Finally the authors review how TVA has been applied to study attentional functions in neuropsychological, pharmacological, and genetic research.

scholarly journals Neuromuscular adjustments of gait associated with unstable conditions

2015 ◽  
Vol 114 (5) ◽  
pp. 2867-2882 ◽  
Author(s):  
G. Martino ◽  
Y. P. Ivanenko ◽  
A. d'Avella ◽  
M. Serrao ◽  
A. Ranavolo ◽  
...  
Keyword(s):  
Muscle Activity ◽  
Gait Cycle ◽  
Activity Patterns ◽  
Human Locomotion ◽  
Support Surface ◽  
Muscle Activations ◽  
The Right ◽  
Weighting Coefficients ◽  
Synergistic Muscle ◽  
Non Negative Matrix Factorization

A compact description of coordinated muscle activity is provided by the factorization of electromyographic (EMG) signals. With the use of this approach, it has consistently been shown that multimuscle activity during human locomotion can be accounted for by four to five modules, each one comprised of a basic pattern timed at a different phase of gait cycle and the weighting coefficients of synergistic muscle activations. These modules are flexible, in so far as the timing of patterns and the amplitude of weightings can change as a function of gait speed and mode. Here we consider the adjustments of the locomotor modules related to unstable walking conditions. We compared three different conditions, i.e., locomotion of healthy subjects on slippery ground (SL) and on narrow beam (NB) and of cerebellar ataxic (CA) patients on normal ground. Motor modules were computed from the EMG signals of 12 muscles of the right lower limb using non-negative matrix factorization. The unstable gait of SL, NB, and CA showed significant changes compared with controls in the stride length, stride width, range of angular motion, and trunk oscillations. In most subjects of all three unstable conditions, >70% of the overall variation of EMG waveforms was accounted for by four modules that were characterized by a widening of muscle activity patterns. This suggests that the nervous system adopts the strategy of prolonging the duration of basic muscle activity patterns to cope with unstable conditions resulting from either slippery ground, reduced support surface, or pathology.

scholarly journals Three-Dimensional Binocular Kinematics of Torsional Vestibular Nystagmus During Convergence on Head-Fixed Targets in Humans

2001 ◽  
Vol 86 (1) ◽  
pp. 113-122 ◽  
Author(s):  
O. Bergamin ◽  
D. Straumann
Keyword(s):  
Human Subjects ◽  
Three Dimensional ◽  
Vertical Component ◽  
Vestibular Stimulation ◽  
Fixed Target ◽  
Healthy Human ◽  
Retinal Slip ◽  
Gain Reduction ◽  
The Right ◽  
Eye Velocity

When a human subject is oscillated about the nasooccipital axis and fixes upon targets along the horizontal head-fixed meridian, angular eye velocity includes a vertical component that increases with the horizontal eccentricity of the line-of-sight. This vertical eye movement component is necessary to prevent retinal slip. We asked whether fixation on a near head-fixed target during the same torsional vestibular stimulation would lead to differences of vertical eye movements between the right and the left eye, as the directions of the two lines-of-sight are not parallel during convergence. Healthy human subjects ( n = 6) were oscillated (0.3 Hz, ±30°) about the nasooccipital axis on a three-dimensional motor-driven turntable. Binocular movements were recorded using the dual search coil technique. A head-fixed laser dot was presented 1.4 m (far head-fixed target) or 0.25 m (near head-fixed target) in front of the right eye. We found highly significant ( P < 0.01) correlations (R binocular = 0.8, monocular = 0.59) between the convergence angle and the difference of the vertical eye velocity between the two eyes. The slope of the fitted linear regression between the two parameters ( s = 0.45) was close to the theoretical slope necessary to prevent vertical retinal slippage (predicted s = 0.5). Covering the left eye did not significantly change the slope ( s = 0.52). In addition, there was a marked gain reduction (∼35%) of the torsional vestibuloocular reflex (VOR) between viewing the far and the near targets, confirming earlier results by others. There was no difference in torsional gain reduction between the two eyes. Lenses of +3 dpt positioned in front of both eyes to decrease the amount of accommodation did not further change the gain of the torsional VOR. In conclusion, ocular convergence on a near head-fixed target during torsional vestibular stimulation leads to deviations in vertical angular velocity between the two eyes necessary to prevent vertical double vision. The vertical deviation velocity is mainly linked to the amount of convergence, since it also occurs during monocular viewing of the near head-fixed target. This suggests that convergence during vestibular stimulation automatically leads to an alignment of binocular rotation axes with the visual axes independent of retinal slip.

Spinal excitation and inhibition decrease as humans age

2004 ◽  
Vol 82 (4) ◽  
pp. 238-248 ◽  
Author(s):  
Aiko Kido ◽  
Naofumi Tanaka ◽  
Richard B Stein
Keyword(s):  
Human Subjects ◽  
Tibialis Anterior Muscle ◽  
Common Peroneal Nerve ◽  
Reciprocal Inhibition ◽  
H Reflex ◽  
Direct Stimulation ◽  
Voluntary Activity ◽  
Healthy Human ◽  
Wide Range ◽  
First Time

Although changes in the soleus H-reflex (an electrical analog of the tendon jerk) with age have been examined in a number of studies, some controversy remains. Also, the effect of age on inhibitory reflexes has received little attention. The purpose of this paper was to examine some excitatory and inhibitory reflexes systematically in healthy human subjects having a wide range of ages. We confirmed that both the maximum H-reflex (Hmax) and the maximum M-wave (Mmax) (from direct stimulation of motor axons) decrease gradually with age. The decrease in Hmax was larger so the Hmax/Mmax ratio decreased dramatically with age. Interestingly, the modulation of the H-reflex during walking was essentially the same at all ages, suggesting that the pathways that modulate the H-reflex amplitude during walking are relatively well preserved during the aging process. We showed for the first time that the short-latency, reciprocal inhibitory pathways from the common peroneal nerve to soleus muscle and from the tibial nerve to the tibialis anterior muscle also decreased with age, when measured as a depression of ongoing voluntary activity. These results suggest that there may be a general decrease in excitability of spinal pathways with age. Thus, the use of age-matched controls is particularly important in assessing abnormalities resulting from disorders that occur primarily in the elderly.Key words: H-reflex, reciprocal inhibition, age.

Reductions in phenomenological, physiological and attentional indices of depressive mood after 2 Hz rTMS over the right parietal cortex in healthy human subjects

2003 ◽  
Vol 120 (1) ◽  
pp. 95-101 ◽  
Author(s):  
Jack van Honk ◽  
Dennis J.L.G. Schutter ◽  
Peter Putman ◽  
Edward H.F de Haan ◽  
Alfredo A.L d'Alfonso
Keyword(s):  
Parietal Cortex ◽  
Human Subjects ◽  
Depressive Mood ◽  
Healthy Human ◽  
Healthy Human Subjects ◽  
The Right

scholarly journals High-human acuity of speed asymmetry during walking

2020 ◽  
Author(s):  
Pablo A. Iturralde ◽  
Marcela Gonzalez-Rubio ◽  
Gelsy Torres-Oviedo
Keyword(s):  
Motor System ◽  
Environmental Changes ◽  
Human Subjects ◽  
Reaction Times ◽  
Internal Variable ◽  
Motor Output ◽  
Perceptual Task ◽  
Drift Diffusion Model ◽  
Motor Impairments ◽  
Healthy Human

1AbstractDespite its central role in the proper functioning of the motor system, sensation has been less studied than motor output in sensorimotor adaptation paradigms. This deficit is probably due to the difficulty of measuring sensation: while motor output has easily observable consequences, sensation is by definition an internal variable of the motor system. In this study we asked how well can subjects estimate relevant environmental changes inducing motor adaptation. We addressed this question in the context of walking on a split-belt treadmill, which allows subjects to experience distinct belt speeds for each leg. We used a two-alternative forced-choice perceptual task (2AFC) in which subjects report which belt they thought to be moving slower. We characterized baseline accuracy in this task for healthy human subjects, and found 75% accuracy for 75 mm/s speed differences. Additionally, we used a drift-diffusion model of the task that could account for both accuracy and reaction times. We conclude that 2AFC tasks can be used to probe subjects’ estimates of the environment and that this approach opens an avenue for investigating perceptual deficits and its relation to motor impairments in clinical populations.

scholarly journals Disentangling reward processes underlying payoff maximization from individual differences in gain frequency bias and reinforcement learning

2021 ◽  
Author(s):  
Pragathi Priyadharsini Balasubramani ◽  
Juan Diaz-Delgado ◽  
Gillian Grennan ◽  
Mariam Zafar-Khan ◽  
Fahad Alim ◽  
...  
Keyword(s):  
Reinforcement Learning ◽  
Individual Differences ◽  
Human Subjects ◽  
Reward Processing ◽  
Anterior Cingulate ◽  
Beta Activity ◽  
Neural Basis ◽  
Healthy Human ◽  
Specific Symptom ◽  
The Right

Humans make choices based on both reward magnitude and reward frequency. Probabilistic decision making is popularly tested using multi-choice gambling paradigms that require participants to maximize task payoff. However, research shows that performance in such paradigms suffers from individual bias towards the frequency of gains as well as individual differences that mediate reinforcement learning, including attention to stimuli, sensitivity to rewards and risks, learning rate, and exploration vs. exploitation based executive policies. Here, we developed a two-choice reward task, implemented in 186 healthy human subjects across the adult lifespan, to understand the cognitive and neural basis of payoff-based performance. We controlled for individual gain frequency biases using experimental block manipulations and modeled individual differences in reinforcement learning parameters. Simultaneously recorded electroencephalography (EEG)-based cortical activations showed that diminished theta activity in the right rostral anterior cingulate cortex (ACC) as well as diminished beta activity in the right parsorbitalis region of the inferior frontal cortex (IFC) during cumulative reward presentation correspond to better payoff performance. These neural activations further associated with specific symptom self-reports for depression (greater ACC theta) and inattention (greater IFC beta), suggestive of reward processing markers of clinical utility.

scholarly journals State-dependent differences in the frequency of TMS-evoked potentials

2019 ◽  
Author(s):  
Candice T. Stanfield ◽  
Martin Wiener
Keyword(s):  
Resting State ◽  
Right Hemisphere ◽  
Human Subjects ◽  
Dominant Frequency ◽  
Healthy Human ◽  
Cortical Areas ◽  
State Dependent ◽  
Concurrent Use ◽  
Cortical Regions ◽  
The Right

AbstractPrevious evidence suggests different cortical areas naturally oscillate at distinct frequencies, reflecting tuning properties of each region. The concurrent use of transcranial magnetic stimulation (TMS) and electroencephalography (EEG) has been used to perturb cortical regions, resulting in an observed post-stimulation response that is maximal at the natural frequency of that region. However, little is known about the spatial extent of TMS-induced activation differences in cortical regions when comparing resting state (passive) versus active task performance. Here, we employed TMS-EEG to directly perturb three cortical areas in the right hemisphere while measuring the resultant changes in maximal evoked frequency in healthy human subjects during a resting state (N=12) and during an active sensorimotor task (N=12). Our results revealed that the brain engages a higher dominant frequency mode when actively engaged in a task, such that the frequency evoked during a task is consistently higher across cortical regions, regardless of the region stimulated. These findings suggest that a distinct characteristic of active performance versus resting state is a higher state of natural cortical frequencies.

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