Motor Time Research Articles

Differences between the time constant of sensory and motor peripheral nerve fibers: further studies and considerations.

Using a method of latent addition, we previously demonstrated that sensory fibers had time constants that were about three times longer than those of motor fibers. The aim of the present work was to confirm this difference by determining the time constants for single sensory axons by using microneurography and for single motor axons by recording single motor units with bipolar concentric needle electrodes. To determine the influence of the conditioning pulse on the neural time constant, we used both depolarizing and hyperpolarizing conditioning pulses. When hyperpolarizing conditioning pulses at comparable intensity were applied, the tendency was to find shorter time constants than when depolarizing pulses were applied, although still with the motor time constant being slightly shorter. Although the absolute values varied with the different methods, the sensory time constant was generally three times the motor time constant for depolarizing conditioning stimuli, whereas for hyperpolarizing conditioning stimuli the difference dropped to about one and a half. These characteristics improve understanding of the behavior of sensory and motor axons, and, in particular, explain the differential excitability. Determination of neural time constants might prove valuable for clinical use.

Effects of the similarity of required responses on fractionated reaction time.

In a previous study, Ito (1990) who used a rapid two-element force-production task, found that the simple reaction time (RT) to initiate the second element was shorter when a sequence was made up of homogeneous elements than when a sequence was made up of heterogeneous elements. The purpose of the present study was to replicate and extend the earlier experiment by adding a control condition and by fractionating RT into premotor time and motor time. Simple RT, premotor time, and motor time to initiate the first element were not different across conditions, suggesting the possibility of distributed programming of the sequence elements. The homogeneous condition, however, produced shorter simple RT and premotor time to initiate the second element than did the heterogeneous and control conditions, which were not significantly different from each other. These findings were discussed in terms of different programming demand during the RT interval.

Separability and Independence of Dimensions within the Same–Different Judgment Task

Ashby, Townsend, and colleagues have developed an important model for the psychophysical identification task, the general recog- nition theory (also called, decision bound theory), based on multi- dimensional signal detection theory, that has been extended to categorization, Garner filtering, similarity judgments, and preference successfully. The virtue of this theory (and its extensions) is the ability to assess the nature of the perceptual representations of stimuli (e.g., their dimensional interactions), within a single framework and across paradigms. This paper adds to this ability by extending the theory, and related multidimensional perceptual models, to the problem of same–different judgments. Three tasks are described for the example of two-dimensional stimuli. In two of these tasks only one dimension is relevant (component same–different). In the third, both dimensions are deemed relevant (standard same–different). Several theorems concerning both response accuracy and response time have been proved relating the property of perceptual separability to certain response time invariances that can be observed in the component same–different tasks. This property, generally speaking, is the constancy of perception of one dimension when another irrelevant dimension changes in the stimulus. Also, under the assumption of within-trial perceptual indepen- dence, response probabilities, and response times of the two–component tasks can be meaningfully related to those same measures in the standard same–different paradigm, provided motor time variance is minimal.

Effects of time uncertainty and instructed muscle tension on fractionated reaction time

Abstract: An experiment was conducted to examine the effects of time uncertainty and instructed muscle tension on the reaction time of elbow flexion. Twenty‐two right‐handed subjects were asked to respond to an audio stimulus by flexing their right elbow under four conditions (2 time uncertainty × 2 instructed muscle tension). Electromyograms (EMGs) were recorded from the biceps and triceps on the subject's right side. Reaction time was divided into premotor time and motor time, based on the difference between the EMG and elbow flexion response. Analysis of reaction time showed that the effects of time uncertainty and instructed muscle tension were additive. Time uncertainty affected premotor time only, and instructed muscle tension affected motor time only. These results are discussed in terms of the assumption that premotor time is a reflection of the central nervous system and motor time is a reflection to the peripheral muscle system.

RESONANCES OF SYMMETRIC MODES IN SHAFTS COUPLED BY MECHANISMS

The paper is concerned with the resonance behaviour of a non-linear system composed of two parallel shafts coupled together by two mechanisms. It is shown that there is a significant qualitative influence of the motor time constants on the motor torque. At the resonance, two coexisting periodic attractors are found. The existence of catastrophic bifurcations associated with each resonance is demonstrated.

M94 Motor cortex excitability and reaction time in cerebellar degeneration

M94 Motor cortex excitability and reaction time in cerebellar degeneration

KNEE REFLEX FACILITATION INDUCED BY SYNERGISTIC CONTRACTION OF THE CONTRALATERAL LEG IN WEIGHT TRAINED MALES 1217

The purpose of this study was to determine whether graded knee flexion (KF) and knee extension (KE) by the contralateral leg during the patellar (knee) reflex would elicit a graded facilitation(FAC) or inhibition(IHB) of fractionated reflex time. FAC would be indicative of a crossed extensor patterning effect. Five college-aged weight trained males (20.6 yrs, 79.9 kg) reported to the lab on two consecutive days. On day 1,25% and 50% MVC values of isometric KF and KE were found. For the reflex trials, subjects sat with their knee joint angles at 90°, and a bipolar electrode on the motor point. A tendon tap hammer struck the patellar ligament from 60°. Fourteen baseline trials (7 normal, 7 Jendrassik facilitory maneuver, JM) were done each day, followed by 4 conditions, 7 trials each. Conditions were 25% and 50% MVC for both KF and KE of the contralateral leg prior to the knee reflex. Post-condition trials were done to detect if fatigue occurred during testing. Conditions were randomized, and EMG data were collected and analyzed for total reflex time (TRT) and its 2 components, reflex latency (RLT, central) and reflex motor time (RMT, peripheral) for each trial. Thetable summarizes results for days 1 and 2. The 25 and 50% MVC KF condition showed a significant decrease in RMT and TRT. This condition elicits FAC similar to the JM. The 25 and 50% MVC KE showed a significant IHB in TRT and RMT. Since RLT was not affected as seen in untrained people, these data suggest that training status may cause a decrease in RMT and TRT, leading to enhanced motor response during synergistic activity.

長潜時反射活動の変化が動作のパフォーマンスに与える影響

The amplitudes of stretch reflex components are known to be modified according to voluntary movement. Specially, the change in long-latency reflex (M2 component) is bigger than that in spinal stretch reflex during voluntary activity. Therefore it has been considered that the M2 component is related to motor control, and it has been assumed that the change M2 component in motor control changes for the purpose of movement. However, it has not been, studied experimentally whether degree of change in M2 component causes functional differences in muscle tension output. The present study was conducted to investigate what effect the M2 component during reaction movement of wrist flexion or extension had on those movements, and to clarify the degree to which modulation of long-latency activity played a functional role in movement performance. Seventeen healthy men, ranging in age from 20 to 28 participated in the study. A DC torque motor was used to generate sudden angular displacements in the extension direction at the right wrist joint. Analysis of the averaged surface electromyogram recorded from the wrist flexor muscle showed that short- and long-latency reflexes (M1 and M2 components) were evoked by muscle stretching. The results are summarized as follows: 1) The M2 amplitude from flexor muscle was increased during reaction movement in the flexion direction, and decreased in the extension direction conversely. In short, the long-latency reflex activity was task-dependent. 2) In flexion reaction task, the bigger the M2 amplitude was, the smaller the handle movement which was drived by torque motor in the extension direction became. Consequently, there was negative correlation between the increase of M2 amplitude and the shortening of flexion motor time in movement performance. 3) In extension reaction task, smaller M2 amplitude led a faster handle speed in the extension direction. Consequently, there was positive correlation between the decrease of M2 amplitude and the shortening of extension motor time in movement performance. These results reveal that a change of the M2 component is closely related to motor control with supraspinal pathways, and movement performance is subject to the degree of modulation of long-latency activity. This seems to suggest that a change in the long-latency reflex has a functional effect on the voluntary muscle tension output in the initiation of movement.

Finger Pairings in Two-Choice Reaction Time Taskscolon: Does the Between-Hands Advantage Reflect Response Preparation?

Two fractionated RT experiments tested whether the response-preparation or response-implementation hypothesis better accounts for the observation that two-choice reaction time (RT) usually takes longer when the responses are performed by the fingers of the same hand (within-hand repertoire) than by the fingers of the two hands (between-hands repertoire). In Experiment I (n equals 8), the effect of repertoire on the premotor time and the motor time were studied. RT was divided into the two periods with respect to the onset of change in electromyographic (EMG) activity of the flexor digitorum profundus. Type of repertoire affected both time periods. In Experiment 2 (n = 16), the effects of repertoire and foreperiod duration on the premotor and motor times of the flexor digitorum profundus and flexor digitorum sublimis were studied. The results of Experiment I were confirmed, and the effects of repertoire and foreperiod duration were found to be additive on premotor time but interactive on motor time. These findings led to rejection of the response-preparation hypothesis and instead supported the view that the central command for the flexion of the right middle finger differs according to the type of repertoire. The command appears to specify a lower rate of recruitment of the prime movers in the within-hand repertoire than in the between-hands repertoire. The execution of the central commands may depend on the state of excitability of the spinal neurons. Analysis of the EMG signals revealed that speed of contraction of the prime movers depends on repertoire when the foreperiod is long but not when it is short. The additivity of the effects of repertoire and of foreperiod duration on premotor time support the view that regardless of the state of preparation of the subject the pattern of EMG activity required for flexion of the right middle finger in each repertoire is specified during the premotor time.

Reaction time (RT) and IQ: Shape of the task complexity function

The shape of the function relating reaction time (RT) and IQ was determined as complexity of the RT-tasks varied. At issue is whether the function is linear or U-shaped. Vernon and Weese ( Personality and Individual Differences, 14, 413–419, 1993) posit a linear task complexity function; i.e. the magnitude of the correlation between RT and IQ increases as RT tasks resemble IQ tests in the demands placed upon Working Memory. Jensen ( Current Directions in Psychological Science, 2, 53–56, 1993) posits a U-shaped function; too-easy and too-hard RT tasks measure non-information processing factors that interfere with the precise measurement of mental speed. Experiment 1 tested 105 university students with paper-and-pencil coding (RT) tests in which task complexity was defined by number of bits of information. Two procedures were used to reduce or eliminate motor time to obtain ‘purer’ measures of mental RT. The results did not support a linear task complexity function; nor were the RT tasks sufficiently difficult to adequately test Jensen's U-shaped function. In Experiment 2, 90 university students were tested with more difficult RT tasks. A definite U-shaped function was obtained with the highest correlation between RT and IQ at an intermediate level of task complexity. When the results of Experiments 1 and 2 were combined, the U-shaped function became even clearer. The results strongly support Jensen's notion that the highest correlation between RT and intelligence is found just below the point at which Working Memory is strained to the point of breakdown and loss of information. The results also support the conception of the Erlangen School that capacity of Working Memory and speed of information processing are determinants of IQ.

Effect of circumferential pressure on response parameters during ballistic ankle plantar flexion in healthy adults.

This study investigated the effect of circumferential pressure on timing and muscle-response parameters during ballistic ankle plantar flexion in 15 young healthy subjects. Circumferential pressure was provided by an air-splint applied around the lower calf. Data were collected at 1, 3, and 5 min. prior to, during, and following application of pressure. A 3 x 3 repeated-measures analysis of variance indicated significant increases in premotor and reaction times during application of pressure. There was no main effect for magnitude of muscle activity or motor time. Results support previous studies showing decreases in the excitability of the motor-neuron pool with circumferential pressure and an inverse relationship between excitability and premotor time.

Essential Tremor Entrains Rapid Voluntary Movements

The effect of essential tremor on the timing of rapid wrist flexion was examined in 10 patients with moderate to severe disability. The mean reaction time and motor time of the patients did not differ from the mean values of 10 healthy age- and sex-matched controls. The latencies of the triphasic agonist and antagonist EMG bursts did not differ between patients and controls. The initiation of movement was time-locked to the tremor cycle in all patients. The initial agonist muscle activation occurred in phase with the rhythmic bursts of EMG, but the onset of rapid wrist flexion occurred when the momentum of essential tremor opposed the volitional movement. Essential tremor has subtle effects on motor control that transcend oscillation per se. These effects probably contribute to the impaired performance of fine motor tasks in patients with advanced disease.

急速な下顎随意運動に伴う胸鎖乳突筋の共同筋活動に関する研究 第２報 開口運動時に認められた予測的頭位調節機構について

Postural adjustments and voluntary movement appear to be parts of thesame motor program. Anticipatory postural movements should result from muscular functionalsynergies selected from a pre-evaluation of the perturbative aspects of the forthcoming movement. The present study was designed to investigate the relationship between anticipatory postural activities of the sternocleidomastoid muscle (SCM) and peripheral processes associated with execution of the voluntary movement. When subjects executed wide jaw opening as rapidly as possible at the acoustic signal, the following results were obtained:1. Relations between firing latencies of the SCM and reaction time (RT) were highly signifi-cant. However, firing latencies of the SCM had no relation with motor time (MT).2. Anticipatory postural period of SCM's activities which preceded the burst of Da had no correlation with opening distance, opening velocity, and MT. These results suggested that anticipatory postural activities of SCM were not associated with peripheral processes of voluntary rapid jaw opening.

Adaptive Velocity Control of DC Motors With Coulomb Friction Identification

A new dc motor control technique for the Coulomb friction compensation is proposed. The technique uses an adaptive velocity control scheme for a dc servo motor with on-line estimated parameters, including a Coulomb friction parameter, which is a combination of the Coulomb friction torque, motor time constant, moment of inertia of the motor, and sampling time of the discrete-time motor model. The estimation model used in the adaptive control process is validated off-line by a pseudo-linear regression algorithm for system parameters in a linear ARMAX model, and by adaptive Kalman filters for the Coulomb friction parameter described as pseudo-random binary sequences. The adaptive controller consists of a friction compensator and a PID controller, whose gains are adjusted adaptively in terms of estimated parameters. The proposed adaptive control law is implemented and tested on a microprocessor-based dc servo motor, and is applicable to many dc-motor-driven precision servo mechanisms. Experimental results are shown to be superior to those of conventional PID controls in terms of parameter fluctuation.

Age and weight effects on motor nerve conduction time measurements in an asymptomatic industrial population

Motor conduction delay has been demonstrated in patients with carpal tunnel syndrome (CTS), however, there is also evidence that conduction slowing can be effected by other factors, e.g., the aging process. Recent development of the digital electroneurometer, a hand-held, battery-powered device for measuring motor nerve conduction time, has made this test available for CTS screening in industry. A cross-sectional study of 77 industrial workers was performed to determine the relationship between median motor nerve conduction time at the carpal tunnel and select personal factors. Motor nerve conduction time increased with age, length of employment, and weight. However, these variables accounted for only 20.3% of the variance in conduction time. The study indicates users of this device should be aware of these effects, and that other sources of variation must be identified and controlled if motor nerve conduction tests are to be used for CTS screening in industry.

A comparison of the effect of lofepramine, maprotiline and placebo on information processing in healthy volunteers

AbstractSingle oral doses of lofepramine (140 mg), maprotiline (100 mg), and placebo were administered in a randomized three‐way crossover design with 1 week wash‐out between administrations to 12 healthy male volunteers. Before, and 1, and 3 h post‐administration a battery of performance tests was administered which included a digit‐matching paradigm and a reaction test separating recognition and motor time. In contrast to maprotiline, lofepramine did not impair speed and accuracy of cognitive performance.

Experimental Determination of Equivalent Circuit Parameters for PM Synchronous Motors

ABSTRACT A full procedure; is presented in this paper to provide a straightforward tool useful for parameter determination of Permanent Magnet Synchronous Motors. Classical tests, that are well established to measure the parameters of synchronous machines with conventional field excitation, are reviewed to confirm or not their applicability. A novel test performed during particular transient conditions allows us to evaluate one of the concerned motor time constants. The motor behaviour is simulated by means of a simulation language (ACSL) on a digital computer and several runs in different transient conditions are performed. Comparison of the simulated and experimental vaweforms of speeds and currents shows good agreement and confirms the validity of the proposed procedure.

Electromechanical delay: An experimental artifact

The time delay between the onset of muscle activation and the onset of force or motion is commonly referred to as electromechanical delay, motor time, or motor execution time. This time has been used in the study of reaction time, of physiological properties of muscle, and of population differences. In this study, we show that electromechanical delay is comprised of two components. The first is transport time ( t t ) which is very brief (perhaps 10 ms). The second is the time to generate detectable changes in force ( t f ). The absolute duration of electromechanical delay is usually dominated by the second component which is influenced by four separate factors that are related in the following way: f = g T R Z d Z m That is, t f is a function ( g) of the product of two ratios. One is between the threshold T of the measuring device and the rate R at which muscle force rises. The other is the ratio of the mechanical impedances of the measuring device ( Z d ) and the muscle ( Z m ). We conclude that the measured absolute value of electromechanical delay has no physiological or psychological meaning and that task and performance induced changes need great care in their interpretation.

Effects of Speed and Accuracy of Exertion of Force on the Relationship between Force Output and Fractionated Reaction Time

The present study was designed to investigate the effect of speed and accuracy of force exertion on the relationship between force output and fractionated reaction time. Subjects exerted their force (10% or 40% of maximum isometric contraction) on "accurate" and "fast" tasks as rapidly as possible at the light signal. On the "fast" task, premotor time for the 40% target was lengthened in comparison with that for the 10% target, and motor time was shortened with an increase of force output. On the "accurate" task, on the other hand, premotor time was independent of magnitude of force, and no relation between motor time and force output was found. These findings show that the relationship between force output and fractionated reaction time may be affected by the effort to exert force accurately.

Fractionated Reaction Times and Movement Times of Down Syndrome and Other Adults with Mental Retardation

A fractionation technique was employed to determine the locus of reaction time delay in Down syndrome (DS) and other adult subjects with mental retardation (MH). Twenty-three subjects (8 nondisabled, 8 MH, and 7 DS) responded to a light, sound, and combination light/sound signal. Dependent measures of premotor time, motor time, total reaction time, and movement time were obtained during a 20° elbow extension movement and were analyzed separately. As expected, both MH and DS subjects were slower and more variable in their responses than the subjects without disabilities. In turn, DS subjects were significantly slower but not more variable than the MH subjects. There were no significant differences between the DS and MH subjects on movement times. Evidence for both a specific (premotor) and a generalized (both premotor and motor) locus of delay was found. Some difference in signal effect was also found for the DS subjects.