Common modulation of motor unit pairs during slow wrist movement in man

Kakuda, Naoyuki; Nagaoka, Masanori; Wessberg, Johan

doi:10.1111/j.1469-7793.1999.00929.x

Cited by 72 publications

(73 citation statements)

References 46 publications

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“…Furthermore, there is evidence that synchronization of motor units in the first dorsal interosseus is greater during eccentric compared with concentric contractions (32), which can potentially increase the fluctuations in acceleration (37,47). Alternatively, the fluctuations in acceleration might be a consequence of the common modulation of motor unit discharge (16,20).…”

Section: Discussionmentioning

confidence: 99%

“…The power spectrum for acceleration has been associated with the discharge pattern of the motor units (16,20), whereas the EMG spectrum has been used to characterize changes in the activation signal sent by the nervous system to the muscle. Preliminary analyses indicated no significant differences (P Ͼ 0.05) in the frequency content of the acceleration and interference EMG (absolute power, median frequency, and the frequency where peak power occurred) for the three trials at a given velocity performed by each subject.…”

Section: Methodsmentioning

confidence: 99%

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Fluctuations in acceleration during voluntary contractions lead to greater impairment of movement accuracy in old adults

Christou

Shinohara

Enoka

2003

Journal of Applied Physiology

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Christou, Evangelos A., Minoru Shinohara, and Roger M. Enoka. Fluctuations in acceleration during voluntary contractions lead to greater impairment of movement accuracy in old adults. J Appl Physiol 95: 373-384, 2003. First published March 21, 2003 10.1152/japplphysiol.00060. 2003.-The purpose of the study was to assess the effect of movement velocity on the relation between fluctuations in acceleration and the ability to achieve a target velocity during voluntary contractions performed by young (29.5 Ϯ 4.3 yr) and old (74.9 Ϯ 6.2 yr) adults. Subjects performed concentric and eccentric contractions with the first dorsal interosseus muscle while lifting a submaximal load (15% of maximum) at six movement velocities (0.03-1.16 rad/s). Fluctuations in acceleration, the accuracy of matching the target velocity, and electromyographic (EMG) activity were determined from three trials for each contraction type and movement velocity. The fluctuations in acceleration increased with movement velocity for both concentric and eccentric contractions, but they were greatest during fast eccentric contractions (ϳ135%) when there was stronger modulation of acceleration in the 5-to 10-Hz bandwidth. Nonetheless, EMG amplitude for first dorsal interosseus increased with movement velocity only for concentric and not eccentric contractions. Consistent with the minimum variance theory, movement accuracy was related to the fluctuations in acceleration for both types of contractions in all subjects. For a given level of fluctuations in acceleration, however, old subjects were three times less accurate than young subjects. Although the EMG amplitude at each speed was similar for young and old adults, only the young adults modulated the power in the EMG spectrum with speed. Thus the fluctuations in acceleration during voluntary contractions had a more pronounced effect on movement accuracy for old adults compared with young adults, probably due to factors that influenced the frequency-domain characteristics of the EMG. concentric contraction; eccentric contraction; electromyogram; first dorsal interosseus; frequency spectrum THE FORCE EXERTED BY A MUSCLE during a voluntary contraction is not constant, but rather it fluctuates about an average value (2,15,25,33,36). The neural mechanisms most responsible for the fluctuations in the force exerted by hand muscles appear to be the regularity with which motoneurons discharge action potentials and the common modulation of motor unit discharge in the agonist and antagonist muscles (7,10,13,16,41). Fluctuations in muscle force impose a significant constraint on the ability of the nervous system to control movement by influencing the capacity to exert a desired force and to achieve an intended trajectory (17,18,43).The minimum variance theory postulates that the central nervous system attenuates this constraint during the performance of goal-directed movements by selecting activation strategies that minimize the variance in the trajectory of the movement (18,43). One prediction of this theory is t...

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Fluctuations in acceleration during voluntary contractions lead to greater impairment of movement accuracy in old adults

Christou

Shinohara

Enoka

2003

Journal of Applied Physiology

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“…This is in contrast to several previous studies on finger and hand muscles. [20][21][22][23][24][25] Vallbo et al 2 0 observed 10Hz oscillation during slow ramp finger movements and Kakuda et al 2 1 reported 6-12 Hz coherence between motor units during the movement phase of slow finger movements, which decreased during position holding. Thus they suggested that the 6-12 Hz input is specific for movements and is normally absent or much weaker during steady maintenance of position or force.…”

Section: Discussionmentioning

confidence: 99%

“…Cortical activity in the [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Hz range has been shown to be coherent with oscillatory EMG activity in contralateral hand and forearm muscles in monkeys and humans. 1,[4][5][6][7][8][9] However, the functional significance of this corticomuscular coherence is unclear.…”

Section: Introductionmentioning

confidence: 99%

Task-and Phase-related Changes in Cortico-muscular Coherence

Masakado

Nielsen

2008

Keio J. Med.

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Cortico-muscular coherence was compared during ramp-and-hold isometric and quasi-isotonic contraction of the ankle joint in human subjects. EEG was recorded from the leg area of the motor cortex. EMG was recorded from the tibialis anterior (TA) muscle. The subjects were requested to maintain a steady low level of dorsiflexion and at intervals of 10 s to increase the contraction level within 1 s, maintain this level for 4 s and then decrease the level of contraction again within another 1 s.In seven subjects coherence in the 15-35 Hz frequency band was seen between EEG and TA EMG during low-level tonic dorsiflexion. In all subjects coherence disappeared during the ramp phase for both isometric and quasi-isotonic contraction. Coherence at other frequencies was also not observed in any of the subjects during the ramp phase. During the hold phase at the stronger level of contraction coherence reappeared quickly and had the same size as at the low level of contraction. However, a significantly larger level of coherence was found during quasi-isotonic than during the isometric contraction.This

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“…Also, several studies used trial durations far shorter than the shortest duration studied here, which would preclude detection of significant coherence except for very high levels. For example, coherence measurements have been applied to trials that were only 5 seconds (Kakuda et al, 1999) and 8 seconds (Kilner et al, 2002) long. The broad range of study parameters demonstrates the need to assess how these choices affect coherence incidence.…”

Section: Discussionmentioning

confidence: 99%

How computational technique and spike train properties affect coherence detection

Terry

Griffin

2008

Journal of Neuroscience Methods

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Spike train coherence is used to characterize common inputs that drive motor unit synchronization. However, data segmentation, overlap, and taper can affect coherence magnitude, thereby influencing the incidence at which significant coherence is detected. Also, the effect of spike train firing rate and common input variability on the detection of significant coherence is unknown. We used a pool of simulated synchronized spike trains with various firing rates (7-19 Hz), coefficients of variation (CV) (0.05-0.50), common input frequencies (10, 20, and 30 Hz, CV: 0.05-0.50), trial durations (30, 60, 90 and 120 sec.), and synchronization strength to explore the effects of segment length (1024 and 2048 1-ms samples), tapering (Hann, Nuttall, and rectangular), and overlap (0, 37.5, 50, 62.5, and 75%). Tapered segments overlapped by at least 50% maximized coherence, regardless of taper type. Coherence for 30-second trials revealed significant coherence for less than half of the motor unit pairs, demonstrating the advantages of longer trails. 2048-sample segments produced similar coherence values with twice the frequency resolution. Increasing the common input variability from 0.15-0.50 reduced coherence incidence by approximately 60%, indicating that synchronized physiological motor unit pairs may fail to show significant coherence if the common input frequency is sufficiently unstable.

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Common modulation of motor unit pairs during slow wrist movement in man

Cited by 72 publications

References 46 publications

Fluctuations in acceleration during voluntary contractions lead to greater impairment of movement accuracy in old adults

Fluctuations in acceleration during voluntary contractions lead to greater impairment of movement accuracy in old adults

Task-and Phase-related Changes in Cortico-muscular Coherence

How computational technique and spike train properties affect coherence detection

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