Organization of inputs to motoneurone pools in man.

Abstract

1. Surface EMGs were recorded from pairs of muscles involved in movements of the wrist and/or digits in the upper limb and from pairs of intrinsic foot muscles in the lower limb during voluntary isometric contractions. 2. EMGs were also recorded from lower limb and trunk muscles during three different tasks: lying, standing and balancing. 3. To investigate if the co‐contraction of muscles was due to the presence of a common drive to each of the two motoneurone pools, cross‐correlation analysis of the two multiunit EMG signals was used. 4. Evidence for a common drive was seen between pairs of muscles that share a common joint or joint complex (such as the metacarpophalangeal joints); no evidence was found for a common drive to co‐contracting muscles that did not share a common joint. 5. When considering analogous hand and foot muscle pairs, the degree of synchrony was significantly greater for lower limb pairs. 6. Where a common drive was detected with lower limb muscle pairs, the degree of synchrony was significantly larger during balancing than during either lying or standing. 7. The origin of the common drive is discussed. It is concluded that activity in both last‐order branched presynaptic fibers and presynaptic synchronization is involved.

The influence of visual information on multi-muscle control during quiet stance: a spectral analysis approach

“…This finding suggests that under the experimental circumstances investigated here, the M-modes are likely formed based on their functional role of moving the body either backward of forward, rather than based on their anatomical location. In addition, similar previous studies have shown evidence for common drive only present between pairs of muscles that share a common joint complex (e.g., Gibbs et al 1995). The functional role of the distribution of common neural inputs is also supported by the results showing no significant values of intermuscular coherence for those signals recorded from pairs of non-synergistic muscles (mixed group).…”

“…It was only by the inclusion of an additional major M-mode that allowed us to investigate the role of common neural inputs in the formation of multi-muscle synergistic groups. We hypothesized that muscles comprising each of these synergistic groups would be coordinated by correlated neural inputs (Gibbs et al 1995) and hence will exhibit significant values of intermuscular coherence.…”

Common Input across Motor Nuclei Mediating Precision Grip in Humans

“…Fewer studies, however, have examined synchrony for pairs of motor units residing in different muscles. The limited data available indicate that synchrony is absent for certain combinations of muscles, for example, between extensor carpi radialis and extensor digitorum (Gibbs et al, 1995). For other sets of muscle combinations, synchrony has been shown to exist but always to a lesser extent than for motor units residing within the same muscle (Bremner et al, 1991a,b;Gibbs et al, 1995).…”

“…The limited data available indicate that synchrony is absent for certain combinations of muscles, for example, between extensor carpi radialis and extensor digitorum (Gibbs et al, 1995). For other sets of muscle combinations, synchrony has been shown to exist but always to a lesser extent than for motor units residing within the same muscle (Bremner et al, 1991a,b;Gibbs et al, 1995). The muscle combinations examined thus far that exhibit significant synchrony usually involve neighboring muscles or muscle compartments (Bremner et al, 1991b, Keen andFuglevand, 2004;Reilly et al, 2004) (cf.…”

Role of across-muscle motor unit synchrony for the coordination of forces

“…However, the above evidence from multi-digit grasping studies prompts questions that must be addressed by studying the behavior of motor units belonging to different muscles. Although several studies have reported across-muscle synchronization (Bremner et al 1991a(Bremner et al ,1991b(Bremner et al ,1991cGibbs et al 1995;Huesler et al 2000;Hockensmith and Fuglevand 2000), this phenomenon deserves further investigation. In particular, what needs to be determined is the functional consequences of across-muscle synchronization.…”