# Last edited on 2013-11-12 18:23:54 by stolfilocal


MUSCULAR SIGNALS

  Psychophysiology, volume 38 (2001), pages 22--34. 
  Optimal signal bandwidth for the recording of surface
  EMG activity of facial, jaw, oral, and neck muscles
  A. van Boxtel

    The motor unit impulse train of the corrugator supercilii muscle is a series of "dirac"
    pulses with mean frequency 31 Hz, resulting in a narrow peak in the power spectrum at that 
    frequency with about ±4 Hz spread, and a lower and broader peak at the first harmonic
    62 ± 8Hz.  Higher harmonics merge into an even broader long-tailed hump peaking at about 93 Hz.
    The frontalis, zygomaticus major,orbicularis oris, and mylohyoideus.

    The surface EMG signal of the orbicularis oculii muscle is more complex, with no definite
    spectral peak, suggesting multiple motor mechanisms with different firing rates.
    Its spectrum is a broad long-tailed hump peaking at about 64 Hz.

    A high-pass filter with cutoff frequency 20 Hz seemed adequate to remove the artifacts
    while retaining the narrow peak when present.

  doi: 10.1152/jn.00009.2006
  Journal of Neurophysiology volume 96 pages 1646-1657 (2006)
  Decomposition of Surface EMG Signals
  Carlo J. De Luca, Alexander Adam, Robert Wotiz, L. Donald Gilmore and S. Hamid Nawab

    The orbicularis oculii muscle appears to be activated by a hierarchy of several independent motor
    units, that are activated in sequence on closing and deactivated in the opposite sequence
    on opening.  Experiments decompse the skin signal into 4 separate pulse trains with 
    somewhat different and varying frequencies. Units 1 (first to start, last to stop)
    and 2 have peak firing rate 20 to 25 Hz. Units 3 and 4 have peak firing rates 10 to 15 Hz.