Superposition of Motor Commands in the Course of Creating 'Two-Joint' Static Efforts by Human Hand Muscles

2012 ◽  
Vol 3 (4) ◽  
pp. 309-318
Author(s):  
Inna V. Vereshchaka ◽  
Andriy V. Gorkovenko
Keyword(s):  
Human Hand ◽  
Hand Muscles ◽  
Motor Commands

scholarly journals Superposition of the motor commands during creation of static efforts by human hand muscles

2012 ◽  
Vol 58 (1) ◽  
pp. 43-50 ◽  
Author(s):  
IV Vereshchaka ◽  
◽  
AV. Horkovenko ◽  
Keyword(s):  
Human Hand ◽  
Hand Muscles ◽  
Motor Commands

Evidence that low-threshold muscle afferents evoke long-latency stretch reflexes in human hand muscles

1991 ◽  
Vol 65 (5) ◽  
pp. 1089-1097 ◽  
Author(s):  
J. Noth ◽  
M. Schwarz ◽  
K. Podoll ◽  
F. Motamedi
Keyword(s):  
Index Finger ◽  
Angular Displacement ◽  
Metacarpophalangeal Joint ◽  
Muscle Afferents ◽  
Human Hand ◽  
Hand Muscles ◽  
Long Latency ◽  
M2 Response ◽  
Spinal Afferents ◽  
Wrist Flexors

1. The aim of the present study was to identify the type of spinal afferents involved in the generation of the long-latency response in intrinsic human hand muscles. Position-controlled extensions were imposed on the index finger or on the wrist of healthy subjects who were exerting a steady voluntary flexion force at the relevant joint. Averaged surface electromyographic (EMG) responses of the first dorsal interosseus muscle (FDI) or of the wrist flexors were evaluated with respect to latency and size. 2. Small transient angular displacements of the index finger (1 degree, as measured at the metacarpophalangeal joint), which are supposed to excite primary rather than secondary afferents, evoked two clearly discernible EMG responses with mean latencies of 32.3 ms (M1 response) and 54.7 ms (M2 response), respectively. The size of the M2 response exceeded the size of the M1 response by 60%. In the wrist flexors, transient stretch (1 degree) gave rise to a large M1 response (latency 22.8 ms) and a small, inconstent M2 response. 3. Small-amplitude vibration of the index finger elicited EMG responses in the FDI that were qualitatively and quantitatively similar to those seen in response to small transient stretches of the index finger. This was also true for fast ramp-and-hold stretches (stretch velocity 400 degrees/s, amplitude 5 degrees), whereas slow ramp-and-hold stretches (125 degrees/s, 5 degrees) elicited predominantly M2 responses. 4. In the FDI, the mechanical threshold of the M1 and M2 response to the transient angular displacement was approximately 0.15 degrees, with a tendency for the M2 response to appear at a lower threshold.(ABSTRACT TRUNCATED AT 250 WORDS)

Task dependence of muscle synchronization in human hand muscles

Neuroreport ◽  
1998 ◽  
Vol 9 (10) ◽  
pp. 2167-2170 ◽  
Author(s):  
Erhard J. Huesler ◽  
M-C Hepp-Reymond ◽  
V Dietz
Keyword(s):  
Human Hand ◽  
Hand Muscles ◽  
Task Dependence

Location-specific and task-dependent modulation of cutaneous reflexes in intrinsic human hand muscles

2006 ◽  
Vol 117 (2) ◽  
pp. 420-429 ◽  
Author(s):  
Tsuyoshi Nakajima ◽  
Masanori Sakamoto ◽  
Takashi Endoh ◽  
Tomoyoshi Komiyama
Keyword(s):  
Human Hand ◽  
Cutaneous Reflexes ◽  
Hand Muscles ◽  
And Task

Gating of segmental and transcortical reflexes to human hand muscles depends on the mode of innervation

2000 ◽  
Vol 280 (2) ◽  
pp. 127-130
Author(s):  
Simone Wagner ◽  
Anna von Waldenfels ◽  
Hans-Michael Meinck
Keyword(s):  
Human Hand ◽  
Hand Muscles

Muscle temperature, contractile speed, and motoneuron firing rates during human voluntary contractions

1992 ◽  
Vol 73 (6) ◽  
pp. 2457-2461 ◽  
Author(s):  
B. Bigland-Ritchie ◽  
C. K. Thomas ◽  
C. L. Rice ◽  
J. V. Howarth ◽  
J. J. Woods
Keyword(s):  
Firing Rate ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Human Hand ◽  
Firing Rates ◽  
Hand Muscles ◽  
Fatigued Muscle ◽  
Contractile Parameters ◽  
Contraction And Relaxation ◽  
Voluntary Contractions

A study was made of motoneuron firing rates and mechanical contractile parameters during maximum voluntary contraction of human hand muscles. A comparison of muscles that had been fatigued after a 60-s maximum voluntary contraction (MVC) with muscles that were cooled by approximately 5 degrees C showed that the contractile properties, in particular the rates of contraction and relaxation, were similarly affected in both conditions. In contrast, the motoneuron firing rate was affected differently by the two treatments. In the case of the fatigued muscles the motoneuron firing rate was reduced by 36%, as was expected from previous studies, but in the case of the cooled muscles, there was no significant change in the motoneuron firing rate. We conclude that the reflex reduction in the motoneuron firing rate seen in the fatigued muscle is not triggered directly by a change in the mechanical properties of the muscle.

Muscular and Postural Synergies of the Human Hand

2004 ◽  
Vol 92 (1) ◽  
pp. 523-535 ◽  
Author(s):  
Erica J. Weiss ◽  
Martha Flanders
Keyword(s):  
Muscle Activation ◽  
Human Subjects ◽  
Motor Units ◽  
Muscle Synergy ◽  
Human Hand ◽  
Muscle Synergies ◽  
Global Pattern ◽  
Hand Muscles ◽  
Multimodal Function ◽  
Postural Synergies

Because humans have limited ability to independently control the many joints of the hand, a wide variety of hand shapes can be characterized as a weighted combination of just two or three main patterns of covariation in joint rotations, or “postural synergies.” The present study sought to align muscle synergies with these main postural synergies and to describe the form of membership of motor units in these postural/muscle synergies. Seventeen joint angles and the electromyographic (EMG) activities of several hand muscles (both intrinsic and extrinsic muscles) were recorded while human subjects held the hand statically in 52 specific shapes (i.e., shaping the hand around 26 commonly grasped objects or forming the 26 letter shapes of a manual alphabet). Principal-components analysis revealed several patterns of muscle synergy, some of which represented either coactivation of all hand muscles, or reciprocal patterns of activity (above and below average levels) in the intrinsic index finger and thumb muscles or (to a lesser extent) in the extrinsic four-tendoned extensor and flexor muscles. Single- and multiunit activity was generally a multimodal function of whole hand shape. This implies that motor-unit activation does not align with a single synergy; instead, motor units participate in multiple muscle synergies. Thus it appears that the organization of the global pattern of hand muscle activation is highly distributed. This organization mirrors the highly fractured somatotopy of cortical hand representations and may provide an ideal substrate for motor learning and recovery from injury.

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