@article{LaineMartinezValdesFallaetal.2015,
  author    = {Laine, Christopher M. and Martinez-Valdes, Eduardo Andr{\´e}s and Falla, Deborah and Mayer, Frank and Farina, Dario},
  title     = {Motor Neuron Pools of Synergistic Thigh Muscles Share Most of Their Synaptic Input},
  series = {The journal of neuroscience},
  volume    = {35},
  journal   = {The journal of neuroscience},
  number    = {35},
  publisher = {Society for Neuroscience},
  address   = {Washington},
  issn      = {0270-6474},
  doi       = {10.1523/JNEUROSCI.0240-15.2015},
  pages     = {12207 -- 12216},
  year      = {2015},
  abstract  = {Neural control of synergist muscles is not well understood. Presumably, each muscle in a synergistic group receives some unique neural drive and some drive that is also shared in common with other muscles in the group. In this investigation, we sought to characterize the strength, frequency spectrum, and force dependence of the neural drive to the human vastus lateralis and vastus medialis muscles during the production of isometric knee extension forces at 10 and 30\% of maximum voluntary effort. High-density surface electromyography recordings were decomposed into motor unit action potentials to examine the neural drive to each muscle. Motor unit coherence analysis was used to characterize the total neural drive to each muscle and the drive shared between muscles. Using a novel approach based on partial coherence analysis, we were also able to study specifically the neural drive unique to each muscle (not shared). The results showed that the majority of neural drive to the vasti muscles was a cross-muscle drive characterized by a force-dependent strength and bandwidth. Muscle-specific neural drive was at low frequencies (<5 Hz) and relatively weak. Frequencies of neural drive associated with afferent feedback (6 - 12 Hz) and with descending cortical input (similar to 20 Hz) were almost entirely shared by the two muscles, whereas low-frequency (<5 Hz) drive comprised shared (primary) and muscle-specific (secondary) components. This study is the first to directly investigate the extent of shared versus independent control of synergist muscles at the motor neuron level.},
  language  = {en}
}
@misc{MartinezValdesNegroLaineetal.2016,
  author    = {Martinez-Valdes, Eduardo and Negro, Francesco and Laine, Christopher M. and Falla, Deborah L. and Mayer, Frank and Farina, Dario},
  title     = {Identifying motor units in longitudinal studies with high-density surface electromyography},
  series = {Converging clinical and engineering research on neurorehabilitation II},
  volume    = {15},
  journal   = {Converging clinical and engineering research on neurorehabilitation II},
  publisher = {Springer},
  address   = {Cham},
  isbn      = {978-3-319-46669-9},
  issn      = {2195-3562},
  doi       = {10.1007/978-3-319-46669-9_27},
  pages     = {147 -- 151},
  year      = {2016},
  abstract  = {We investigated the possibility to identify motor units (MUs) with high-density surface electromyography (HDEMG) over experimental sessions in different days. 10 subjects performed submaximal knee extensions across three sessions in three days separated by one week, while EMG was recorded from the vastus medialis muscle with high-density electrode grids. The shapes of the MU action potentials (MUAPs) over multiple channels extracted from HDEMG decomposition were matched across sessions by cross-correlation. Forty and twenty percent of the MUs decomposed could be tracked across two and three sessions, respectively (average cross correlation 0.85 +/- 0.04). The estimated properties of the matched motor units were similar across the sessions. For example, mean discharge rate and recruitment thresholds were measured with an intra-class correlation coefficient (ICCs) > 0.80. These results strongly suggest that the same MUs were indeed identified across sessions. This possibility will allow monitoring changes in MU properties following interventions or during the progression of neuromuscular disorders.},
  language  = {en}
}