Organizing principles for single-joint movements. I. A speed-insensitive strategy

1989 ◽  
Vol 62 (2) ◽  
pp. 342-357 ◽  
Author(s):  
G. L. Gottlieb ◽  
D. M. Corcos ◽  
G. C. Agarwal
Keyword(s):  
Human Subjects ◽  
Movement Time ◽  
Muscle Length ◽  
Initial Position ◽  
Inertial Load ◽  
Antagonist Muscles ◽  
Human Movements ◽  
Inertial Torque ◽  
Highly Correlated ◽  
Organizing Principles

1. Normal human subjects made discrete elbow flexions and extensions in the horizontal plane from a stationary initial position to visually defined targets at different distances with a constant inertial load or made flexions to a visually defined target with different inertial loads. We measured joint angle, acceleration, and electromyograms (EMGs) from two agonist and two antagonist muscles. 2. Subjects were instructed to move their limbs accurately but quickly to the targets. Movements of greater distances or lesser loads were performed at higher velocities. 3. Peak inertial torque, acceleration and velocity, movement time, and integrated, rectified EMG were all highly correlated with the task variables, distance and inertial load. We show that peak inertial torque can be used as a linking variable that is almost sufficient to explain all correlations between the tasks, the EMG, and movement kinematics. 4. The rate at which subjects initially developed torque to accelerate their movements was invariant over changes in the value of either task variable. The rising phase of the agonist EMG was also independent of the distance or load moved. 5. Two components were distinguished in the antagonist EMG. The first had a relatively constant latency and amplitude. It terminated on the onset of the second and larger component at a latency that was delayed as both distance and load increased. 6. The integrated, rectified antagonist EMG was proportional to inertial load and peak decelerating torque for changes in inertial load. When target distance varied, proportionality between peak decelerating torque and antagonist EMG could be found if correction was made for the effects of muscle length on the torque-EMG relationship. 7. We propose organizing principles for the control of single-joint human movements in which tasks are performed by one of two strategies. These are called speed-insensitive and speed-sensitive strategies. 8. A model is described in which movements made under a speed-insensitive strategy are executed by controlling the duration and the relative timing of amplitude invariant patterns of activation to the spinal motoneuron pools.

Organizing principles for single-joint movements. II. A speed-sensitive strategy

1989 ◽  
Vol 62 (2) ◽  
pp. 358-368 ◽  
Author(s):  
D. M. Corcos ◽  
G. L. Gottlieb ◽  
G. C. Agarwal
Keyword(s):  
Muscle Activation ◽  
Human Subjects ◽  
Movement Time ◽  
Initial Position ◽  
Joint Torque ◽  
Movement Speed ◽  
Movement Kinematics ◽  
Antagonist Muscles ◽  
Speed Accuracy ◽  
Organizing Principles

1. Normal human subjects made discrete flexions of the elbow over a fixed distance in the horizontal plane from a stationary initial position to a visually defined target. We measured joint angle, acceleration, and electromyograms (EMGs) from two agonist and two antagonist muscles. 2. Changes in movement speed were elicited either by explicit instruction to the subject or by adjusting the target width. Instructions always required accurately stopping in the target zone. 3. Peak inertial torques and accelerations, movement times, and integrated EMGs were all highly correlated with speed. We show that inertial torque can be used as a linking variable that is almost sufficient to explain all correlations between the task, the EMG, and movement kinematics. 4. When subjects perform tasks that require control of movement speed, they adjust the rate at which torque is developed by the muscles. This rate is modulated by the way in which the muscles are activated. The rate at which joint torque develops is correlated with the rate at which the agonist EMG rises as well as with integrated EMG. 5. The antagonist EMG shows two components. The latency of the first is 30-50 ms and independent of movement dynamics. The latency of the second component is proportional to movement time. The rate of rise and area of both components scale with torque. 6. We propose organizing principles for the control of single-joint movements in which tasks are performed by one of two strategies. These are called speed-insensitive and speed-sensitive strategies. 7. A model is proposed in which movements made under a speed-sensitive strategy are executed by controlling the intensity of an excitation pulse delivered to the motoneuron pool. The effect is to regulate the rate at which joint torque, and consequently acceleration, increases. 8. Movements of variable distance, speed, accuracy, and load are shown to be controlled by one of two consistent sets of rules for muscle activation. These rules apply to the control of both the agonist and antagonist muscles. Rules of activation lead to distinguishable patterns of EMG and torque development. All observable changes in movement kinematics are explained as deterministic consequences of these effects.

Organizing principles for single joint movements. III. Speed-insensitive strategy as a default

1990 ◽  
Vol 63 (3) ◽  
pp. 625-636 ◽  
Author(s):  
G. L. Gottlieb ◽  
D. M. Corcos ◽  
G. C. Agarwal ◽  
M. L. Latash
Keyword(s):  
Human Subjects ◽  
Movement Control ◽  
Initial Position ◽  
Initial Slope ◽  
Range Of Movement ◽  
Stationary Target ◽  
Wide Range ◽  
Inertial Torque ◽  
Maximal Speed ◽  
Speed Accuracy

1. Human subjects made discrete elbow flexions in a horizontal plane over different distances, from a stationary initial position to a visually defined stationary target 9 degrees wide. We measured joint angle, acceleration, and electromyograms (EMGs) from two agonist and two antagonist muscles. 2. Subjects made movements over four different distances following one of four different instructions. The first instructed the subject simply to choose a comfortable speed. The other three explicitly emphasized either speed, accuracy, or maintenance of the "same" speed over different distances. These instructions produced a wide range of movement velocities. 3. The initial rises of the acceleration (and therefore of the inertial torque), as well as the initial slope of the agonist EMG, were all invariant over changes in the target distance for any single instruction but were all sensitive to the given instruction. 4. Our results demonstrate that the speed-insensitive strategy is a standard or default pattern for performing movements that may be carried out for different instructions over a wide range of speeds. A uniform intensity of excitation pulse is not a byproduct of moving at maximal speed. Submaximal intensities are associated with submaximal speeds and are a selected feature of the pattern of movement control.

scholarly journals Aging Does Not Affect Beta Modulation during Reaching Movements

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Serena Ricci ◽  
Ramtin Mehraram ◽  
Elisa Tatti ◽  
Aaron B. Nelson ◽  
Martina Bossini-Baroggi ◽  
...  
Keyword(s):  
Modulation Depth ◽  
Movement Time ◽  
Peak Latency ◽  
Reaching Movements ◽  
Performance Indices ◽  
Reaching Task ◽  
Beta Power ◽  
Total Movement ◽  
Older Subjects ◽  
Highly Correlated

During movement, modulation of beta power occurs over the sensorimotor areas, with a decrease just before its start (event-related desynchronization, ERD) and a rebound after its end (event-related synchronization, ERS). We have recently found that the depth of ERD-to-ERS modulation increases during practice in a reaching task and the following day decreases to baseline levels. Importantly, the magnitude of the beta modulation increase during practice is highly correlated with the retention of motor skill tested the following day. Together with other evidence, this suggests that the increase of practice-related modulation depth may be the expression of sensorimotor cortex’s plasticity. Here, we determine whether the practice-related increase of beta modulation depth is equally present in a group of younger and a group of older subjects during the performance of a 30-minute block of reaching movements. We focused our analyses on two regions of interest (ROIs): the left sensorimotor and the frontal region. Performance indices were significantly different in the two groups, with the movements of older subjects being slower and less accurate. Importantly, both groups presented a similar increase of the practice-related beta modulation depth in both ROIs in the course of the task. Peak latency analysis revealed a progressive delay of the ERS peak that correlated with the total movement time. Altogether, these findings support the notion that the depth of beta modulation in a reaching movement task does not depend on age and confirm previous findings that only ERS peak latency but not ERS magnitude is related to performance indices.

Predictive human pursuit and "orbital goal" of microstimulated smooth eye movements

1995 ◽  
Vol 74 (3) ◽  
pp. 1358-1361 ◽  
Author(s):  
P. van Gelder ◽  
S. Lebedev ◽  
W. H. Tsui
Keyword(s):  
Smooth Pursuit ◽  
Human Subjects ◽  
Initial Position ◽  
Common Point ◽  
Frontal Eye Field ◽  
Moving Target ◽  
The Gaze ◽  
Target Trajectory ◽  
Eye Field ◽  
Normal Human

1. Anticipatory saccades in smooth pursuit move the point of gaze from near the moving target to well ahead of it, interrupting accurate smooth pursuit. Their effects on the pursuit process were studied in 22 normal human subjects. We presented horizontal periodic target trajectories of 30 degrees amplitude and 30 degrees/s constant velocity or 0.4 Hz sinusoidal velocity in 40-s trials. Saccades and surrounding smooth eye movement (SEM) segments were marked and classified by computer. 2. Anticipatory saccades were often followed by slowed SEM that tended to intercept the target at the endpoint of its trajectory. This was seen in the distribution of projections of the initial 60 ms of postsaccadic SEM to the time of the trajectory endpoint. Magnitude of this SEM tended to follow a function of the time and location of the endpoint of the anticipatory saccade, decreasing as the anticipatory saccades landed closer to the trajectory endpoint. 3. The time and location of the target trajectory endpoint seemed to be the goal for this SEM. We believe this to demonstrate the predictive use of the period and amplitude of the trajectory in smooth pursuit, apart from the instantaneous velocity match of the target. 4. Gottlieb and coworkers in the frontal eye field and Ron and Robinson in the cerebellum produced SEMs in the monkey by microstimulation. At some sites in both structures, direction and velocity of the SEMs depended on the initial position of the eye in that the elicited SEMs appeared to be converging toward a common point, or "orbital goal", and the SEM velocity diminished as the gaze neared that goal.2+ Both our SEM after anticipatory saccades and microstimulated SEM in the monkey slowed as the initial position was brought closer to the inferred orbital goal. This similarity suggests that the goal-directed SEM sites in the monkey might be part of a mechanism for predictive pursuit.

Variationist typology: Shared probabilistic constraints across (non-)null subject languages

Linguistics ◽  
2019 ◽  
Vol 57 (3) ◽  
pp. 653-692 ◽  
Author(s):  
Rena Torres Cacoullos ◽  
Catherine E. Travis
Keyword(s):  
Temporal Relationship ◽  
Human Subjects ◽  
Variable Structure ◽  
Initial Position ◽  
Probabilistic Constraints ◽  
Null Subject ◽  
Lexical Aspect ◽  
Variation Patterns ◽  
Cross Language ◽  
Key Parameter

Abstract A key parameter in received classifications of language types is the expression of pronominal subjects. Here we compare variation patterns in conversational data of English – considered a non-null-subject language – and Spanish – a well-studied null-subject language. English has a patently lower rate of expression (approximately 3% unexpressed 1sg and 3sg human subjects vs. 60% in Spanish). Despite the stark difference in rate of expression, the same probabilistic constraints are at work in the two languages. Contrary to popular belief, VP coordination is neither a discrete nor a distinguishing category of English. Instead, a shared constraint is linking with the preceding subject, a refinement of accessibility to include, alongside coreferentiality, measures of structural connectedness – both prosodic and syntactic. Other shared constraints on unexpressed subjects are coreferential subject priming (a tendency to repeat the form of the previous mention) and lexical aspect (reflecting the contribution of a temporal relationship to subject expression). Where the languages most differ is in the envelope of variation. In English, besides coreferential-subject verbs conjoined with a coordinating conjunction, unexpressed subjects are limited to prosodic initial-position in declarative main clauses, a restriction that is absent in Spanish. We propose that the locus of cross-language comparisons is the variable structure of each language, defined by the set of probabilistic constraints but also the delimitation of the variable context within which these are operative.

An Acoustical Study of the Fricative /s/ in the Speech of Individuals With Dysarthria

2001 ◽  
Vol 44 (6) ◽  
pp. 1300-1314 ◽  
Author(s):  
Helen Chen ◽  
Kenneth N. Stevens
Keyword(s):  
Time Variation ◽  
Initial Position ◽  
Acoustic Properties ◽  
Normal Range ◽  
Spectrum Shape ◽  
Quantitative Measurements ◽  
Fine Control ◽  
Acoustical Study ◽  
Highly Correlated ◽  
Acoustic Pattern

This paper reports on measurements of several acoustic attributes of the fricative consonant /s/ produced in word-initial position by normally speaking adults and by speakers with neuromotor dysfunctions. Several acoustic properties are evaluated: the spectrum shape of the fricative and its amplitude in relation to the following vowel, the presence or absence of voicing, the time variation of the spectrum during the fricative and in the transition to the following vowel, and the presence of inappropriate acoustic patterns preceding the /s/. Some of these properties are based on quantitative measurements of the spectrum of the /s/, and others are based on observations of the time-varying acoustic patterns in spectrograms. For the individuals with dysarthria, deviations of each of these properties from the normal range are interpreted in terms of specific deficits in the control of the speech-production system. For the most part, these parameters are highly correlated with the speakers' overall intelligibility, with the intelligibility of words containing the fricative /s/, and with perceptual ratings of the adequacy of the fricative production. The parameters that show the best correlation with intelligibility and perceptual ratings are (a) measures of deviations from normalcy in the time variation of the acoustic pattern within the consonant and at the consonant-vowel boundary and (b) the spectrum shape of the frication noise. These acoustic parameters are related to deviations in the temporal pattern of control of the articulators in producing fricative-vowel sequences and to lack of fine control of the tongue blade in achieving an appropriate target configuration for the fricative.

INTRA-, EXTRA- AND INTERMUSCULAR MYOFASCIAL FORCE TRANSMISION OF SYNERGISTS AND ANTAGONISTS: EFFECTS OF MUSCLE LENGTH AS WELL AS RELATIVE POSITION

2002 ◽  
Vol 02 (03n04) ◽  
pp. 405-419 ◽  
Author(s):  
PETER A. HUIJING
Keyword(s):  
Connective Tissue ◽  
Relative Position ◽  
Muscle Length ◽  
Force Transmission ◽  
Muscle Belly ◽  
Myofascial Force Transmission ◽  
Antagonist Muscles ◽  
Length Changes ◽  
Edl Muscle

The concepts of intramuscular myofascial force transmission is reintroduced and reviewed on the basis of experiments involving tenotomy and aponeurotomy of dissected rat EDL muscle studied in situ. Results from experiments with measurements of force of EDL muscle, of which the muscle belly was not dissected (i.e. the muscle is surrounded by its natural connective tissue milieu) are discussed. In such experiments, force was measured at proximal as well as distal EDL tendons. Examples of experimental evidence for both extramuscular and intermuscular myofascial force transmission within the rat anterior crural compartment are presented. Evidence is presented also for differential effects of proximal and distal lengthening on myofascial force transmission from EDL, even for the case in which symmetric length changes were imposed on the muscle. It is shown that myofascial force transmission effects are not limited to synergists located within one compartment, but do also play a very substantial role in the interaction between antagonist muscles in neighbouring anterior crural and peroneal compartments.

scholarly journals Research on the visual cognition patterns of exit guide sign viewing on freeway interchanges

2019 ◽  
Vol 11 (3) ◽  
pp. 168781401881953
Author(s):  
Guichao Ren ◽  
Xiaohua Zhao ◽  
Zhanzhou Lin ◽  
Wenxiang Xu
Keyword(s):  
Eye Movement ◽  
Fixation Duration ◽  
Tracking System ◽  
Movement Time ◽  
Threshold Value ◽  
Visual Cognition ◽  
The Road ◽  
Route Information ◽  
Four Levels ◽  
Highly Correlated

The development of freeway construction and the increasing coverage of the road network have led to increasing requirements for guide signs. This article investigated drivers’ visual cognition pattern regarding exit guide signs on freeway interchanges. A static visual cognition experiment with 32 participants was carried out. The route information volume (four levels) and destination information volume (seven levels) were selected as the variables. An eye-tracking system was utilized to record drivers’ eye movement indicators, such as eye movement time, saccade frequency, seek time, and fixation duration. The results indicated that the eye movement time, saccade frequency, and seek time are highly correlated with information volume and increase significantly with the increases in information volume; although the fixation duration has no correlation with information volume, the fixation duration value, saccade frequency, and seek time of destination information are significantly higher than those of route information, and the destination information fulfills a stronger guiding function during the driver’s trip. The corresponding threshold values of destination information are 5, 5, 4, and 3 under the four levels of route information, and the threshold value of route information is 3.

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