Motor patterns in legged vertebrates show modularity in both young and adult animals, comprising motor synergies or primitives. Are such spinal modules observed in young mammals conserved into adulthood or altered? Conceivably, early circuit modules alter radically through experience and descending pathways' activity. We analyze lumbar motor patterns of intact adult rats and the same rats after spinal transection and compare these with adult rats spinal transected 5 days postnatally, before most motor experience, using only rats that never developed hind limb weight bearing. We use independent component analysis (ICA) to extract synergies from electromyography (EMG). ICA information-based methods identify both weakly active and strongly active synergies. We compare all spatial synergies and their activation/drive strengths as proxies of spinal modules and their underlying circuits. Remarkably, we find that spatial primitives/synergies of adult injured and neonatal injured rats differed insignificantly, despite different developmental histories. However, intact rats possess some synergies that differ significantly, although modestly, in spatial structure. Rats injured as adults were more similar in modularity to rats that had neonatal spinal transection than to themselves before injury. We surmise that spinal circuit modules for spatial synergy patterns may be determined early, before postnatal day 5 (P5), and remain largely unaltered by subsequent development or weight-bearing experience. An alternative explanation but equally important is that, after complete spinal transection, both neonatal and mature adult spinal cords rapidly converge to common synergy sets. This fundamental or convergent synergy circuitry, fully determined by P5, is revealed after spinal cord transection.motor primitives | muscle synergies | pattern generation | spinal cord injury | development M otor patterns can show significant modularity in legged vertebrates. Modularity can take several forms (1). Here, we examine modular motor drives in spinal systems. This approach combines both structural and functional neural components. The fundamental idea is that basic movement is largely composed of small numbers of synergies or motor primitives, which act as building blocks (1-5). Synergies for this study are defined as spatial synergies (1), which each represent a premotor drive to motor pools, causing covarying muscle activity in a specific balance. Such drives could arise from a well-defined neural substrate of sets of neurons with specific premotor connectivity. Indeed, some data in frogs and monkeys support this idea (6, 7). Such modularity could arise as follows: first, directly through evolutionarily determined processes in development; second, through plastic online optimizations during development; third, de novo during motor skill learning; or fourth, via some combinations of these (1,2,4,8). The collection of synergies resulting from any of these processes can form a library of compositional elements useful both for new movement con...

Objective Recent research has shown dissociation between changes in brain and muscle signals during voluntary muscle fatigue, which may suggest weakening of functional corticomuscular coupling. However, this weakening of brain-muscle coupling has never been directly evaluated. The purpose of this study was to address this issue by quantifying EEG-EMG coherence at times when muscles experienced minimal versus significant fatigue. Methods Nine healthy subjects sustained an isometric elbow flexion at 30% maximal level until exhaustion while their brain (EEG) and muscle (EMG) activities were recorded. The entire duration of the EEG and EMG recordings was divided into the first half (stage 1 with minimal fatigue) and second half (stage 2 with severer fatigue). The EEG-EMG coherence and power spectrum in each stage was computed. Results The power of both EEG and EMG increased significantly while their coherence decreased significantly in stage 2 compared with stage 1 at beta (15-35 Hz) band. Conclusions Despite an elevation of the power for both the EEG and EMG activities with muscle fatigue, the fatigue weakens strength of brain-muscle signal coupling at beta frequency. Significance Weakening of corticomuscular coupling may be a major neural mechanism contributing to muscle fatigue and associated performance impairment.

Fractal dimension (FD) has been proved useful in quantifying the complexity of dynamical signals in biology and medicine. In this study, we measured FDs of human electroencephalographic (EEG) signals at different levels of handgrip forces. EEG signals were recorded from five major motor-related cortical areas in eight normal healthy subjects. FDs were calculated using three different methods. The three physiological periods of handgrip (command preparation, movement and holding periods) were analyzed and compared. The results showed that FDs of the EEG signals during the movement and holding periods increased linearly with handgrip force, whereas FD during the preparation period had no correlation with force. The results also demonstrated that one method (Katz's) gave greater changes in FD, and thus, had more power in capturing the dynamic changes in the signal. The linear increase of FD, together with results from other EEG and neuroimaging studies, suggest that under normal conditions the brain recruits motor neurons at a linear progress when increasing the force.

Tumor margin, tumor differentiation, vascular invasion, and lymph node status were independent factors for OS and DFS. Surgical procedures can indirectly affect survival outcome by influencing the tumor resection margin.