scholarly journals Sound-evoked vestibular projections to the splenius capitis in humans: comparison with the sternocleidomastoid muscle

2019 ◽  
Vol 126 (6) ◽  
pp. 1619-1629 ◽  
Author(s):  
Sally M. Rosengren ◽  
Konrad P. Weber ◽  
Sendhil Govender ◽  
Miriam S. Welgampola ◽  
Danielle L. Dennis ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Motor Unit ◽  
Vestibular Function ◽  
Head Rotation ◽  
Neck Muscle ◽  
Vestibular Evoked Myogenic Potential ◽  
Vestibular Loss ◽  
Single Motor Unit ◽  
Single Motor ◽  
Splenius Capitis

The short-latency vestibulo-collic reflex in humans is well defined for only the sternocleidomastoid (SCM) neck muscle. However, other neck muscles also receive input from the balance organs and participate in neck stabilization. We therefore investigated the sound-evoked vestibular projection to the splenius capitis (SC) muscles by comparing surface and single motor unit responses in the SC and SCM muscles in 10 normal volunteers. We also recorded surface responses in patients with unilateral vestibular loss but preserved hearing and hearing loss but preserved vestibular function. The single motor unit responses were predominantly inhibitory, and the strongest responses were recorded in the contralateral SC and ipsilateral SCM. In both cases there was a significant decrease or gap in single motor unit activity, in SC at 11.7 ms for 46/66 units and in SCM at 12.7 ms for 51/58 motor units. There were fewer significant responses in the ipsilateral SC and contralateral SCM muscles, and they consisted primarily of weak increases in activity. Surface responses recorded over the contralateral SC were positive-negative during neck rotation, similar to the ipsilateral cervical vestibular evoked myogenic potential in SCM. Responses in SC were present in the patients with hearing loss and absent in the patient with vestibular loss, confirming their vestibular origin. The results describe a pattern of inhibition consistent with the synergistic relationship between these muscles for axial head rotation, with the crossed vestibular projection to the contralateral SC being weaker than the ipsilateral projection to the SCM. NEW & NOTEWORTHY We used acoustic vestibular stimulation to investigate the saccular projections to the splenius capitis (SC) and sternocleidomastoid (SCM) muscles in humans. Single motor unit recordings from within the muscles demonstrated strong inhibitory projections to the contralateral SC and ipsilateral SCM muscles and weak excitatory projections to the opposite muscle pair. This synergistic pattern of activation is consistent with a role for the reflex in axial rotation of the head.

Rectification is required to extract oscillatory envelope modulation from surface electromyographic signals

2014 ◽  
Vol 112 (7) ◽  
pp. 1685-1691 ◽  
Author(s):  
Christopher J. Dakin ◽  
Brian H. Dalton ◽  
Billy L. Luu ◽  
Jean-Sébastien Blouin
Keyword(s):  
Motor Unit ◽  
Stimulus Frequency ◽  
Motor Units ◽  
Surface Emg ◽  
Medial Gastrocnemius ◽  
Single Motor Unit ◽  
Single Motor ◽  
Single Motor Units ◽  
Emg Signal ◽  
Envelope Modulation

Rectification of surface electromyographic (EMG) recordings prior to their correlation with other signals is a widely used form of preprocessing. Recently this practice has come into question, elevating the subject of EMG rectification to a topic of much debate. Proponents for rectifying suggest it accentuates the EMG spike timing information, whereas opponents indicate it is unnecessary and its nonlinear distortion of data is potentially destructive. Here we examine the necessity of rectification on the extraction of muscle responses, but for the first time using a known oscillatory input to the muscle in the form of electrical vestibular stimulation. Participants were exposed to sinusoidal vestibular stimuli while surface and intramuscular EMG were recorded from the left medial gastrocnemius. We compared the unrectified and rectified surface EMG to single motor units to determine which method best identified stimulus-EMG coherence and phase at the single-motor unit level. Surface EMG modulation at the stimulus frequency was obvious in the unrectified surface EMG. However, this modulation was not identified by the fast Fourier transform, and therefore stimulus coherence with the unrectified EMG signal failed to capture this covariance. Both the rectified surface EMG and single motor units displayed significant coherence over the entire stimulus bandwidth (1–20 Hz). Furthermore, the stimulus-phase relationship for the rectified EMG and motor units shared a moderate correlation ( r = 0.56). These data indicate that rectification of surface EMG is a necessary step to extract EMG envelope modulation due to motor unit entrainment to a known stimulus.

scholarly journals An Analysis or the single Motor Unit Activity Involved in Oro-facial Functions

1986 ◽  
Vol 4 ◽  
pp. 115-122
Author(s):  
Hideho Handa ◽  
Yukihiro Fujita ◽  
Yasuyo Nomora ◽  
Hiroshi Suzuki ◽  
Kazuo Toda ◽  
...  
Keyword(s):  
Motor Unit ◽  
Unit Activity ◽  
Single Motor Unit ◽  
Single Motor ◽  
Motor Unit Activity

Fractionation of the motor unit: response to tetanus

1961 ◽  
Vol 200 (4) ◽  
pp. 689-693
Author(s):  
Simeon Locke
Keyword(s):  
Action Potential ◽  
Motor Unit ◽  
Nerve Terminal ◽  
Differential Effect ◽  
Blocking Agent ◽  
Single Motor Unit ◽  
Single Motor ◽  
Blocking Agents ◽  
Before And After ◽  
Post Tetanic Potentiation

The effect of a tetanus on the motor unit of the gastrocnemius of the rat has been studied before and after administration of blocking agents. Post-tetanic potentiation of action potential of the single motor unit occurs following depression of response by curare or decamethonium. Increased amplitude of unit potential results from partial resynchronization of subunit potential contributions which had been desynchronized by the differential effect of the blocking agent on subunit latency. Decline of unit potential subsequent to post-tetanic potentiation results from desynchronization of component contributions as had been observed with initial administration of blocking agent. The occurrence of these events in a single motor unit indicates that they take place at the nerve terminal or subterminal portion of the unit.

Foreperiod effects on human single motor unit reaction times

1973 ◽  
Vol 10 (3) ◽  
pp. 539-542 ◽  
Author(s):  
Joseph Kimm ◽  
Dwight Sutton
Keyword(s):  
Motor Unit ◽  
Reaction Times ◽  
Single Motor Unit ◽  
Single Motor
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