Cutaneous silent period in human FDI motor units

In this study, we aimed to use both the probability-based and the frequency-based analyses methods simultaneously to examine cutaneous silent period (CSP) induced by strong electrical currents. Subjects were asked to contract their first dorsal interosseus muscles so that one motor unit monitored via intramuscular wire electrodes discharged at a rate of approximately 8 Hz. Strong electrical stimuli were delivered to the back of the hand that created a subjective discomfort level of between 4 and 7 [0–10 visual analogue scale] and induced cutaneous silent period in all units. It was found that the duration of the CSP was significantly longer when the same data were analysed using frequency-based analysis method compared with the probability-based methods. Frequency-based analysis indicated that the strong electrical stimuli induce longer lasting inhibitory currents than what was indicated using the probability-based analyses such as surface electromyogram and peristimulus time histogram. Usage of frequency-based analysis for bringing out the synaptic activity underlying CSP seems essential as its characteristics have been subject to a large number of studies in experimental and clinical settings.

[1]  Y. Laporte,et al.  A method of analysing the responses of spindle primary endings to fusimotor stimulation , 1968, The Journal of physiology.

[2]  Kemal S. Türker,et al.  The lip-clip:A simple, low-impedance ground electrode for use in human electrophysiology , 1988, Brain Research Bulletin.

[3]  P. Ashby,et al.  Synaptic connections to individual tibialis anterior motoneurones in man. , 1978, Journal of neurology, neurosurgery, and psychiatry.

[4]  M. Kofler,et al.  Cutaneous silent periods in intramedullary spinal cord lesions , 2003, Journal of the Neurological Sciences.

[5]  R K Powers,et al.  Effective synaptic current can be estimated from measurements of neuronal discharge. , 1992, Journal of neurophysiology.

[6]  P. Fuhr,et al.  Muscle force up to 50% of maximum does not affect cutaneous silent periods in thenar muscles , 2007, Clinical Neurophysiology.

[7]  A. Drewes,et al.  Experimental human pain models: a review of standardised methods for preclinical testing of analgesics. , 2004, Basic & clinical pharmacology & toxicology.

[8]  J. Duysens,et al.  Phase-dependent modulation of short latency cutaneous reflexes during walking in man , 2005, Brain Research.

[9]  M Hallett,et al.  Cutaneous withdrawal reflexes of the upper extremity , 1998, Muscle & nerve.

[10]  F. Awiszus,et al.  Continuous functions determined by spike trains of a neuron subject to stimulation , 1988, Biological Cybernetics.

[11]  K. Türker,et al.  Motor-unit firing frequency can be used for the estimation of synaptic potentials in human motoneurones , 1994, Journal of Neuroscience Methods.

[12]  J. Stephens,et al.  The reflex responses of single motor units in human first dorsal interosseous muscle following cutaneous afferent stimulation. , 1980, The Journal of physiology.

[13]  K. Türker,et al.  A study of synaptic connection between low threshold afferent fibres in common peroneal nerve and motoneurones in human tibialis anterior , 2008, Experimental Brain Research.

[14]  M. Kofler,et al.  Ipsi- and contralateral exteroceptive EMG modulation in uni- and bilaterally activated thenar muscles , 2005, Clinical Neurophysiology.

[15]  F. Pierelli,et al.  L‐Dopa decreases cutaneous nociceptive inhibition of motor activity in Parkinson's disease , 2002, Acta neurologica Scandinavica.

[16]  A. Berardelli,et al.  Is the cutaneous silent period an opiate‐sensitive nociceptive reflex? , 2002, Muscle & nerve.

[17]  J. Ushiba,et al.  Reassessment of parameters for applying motor-unit triggered stimuli in peri-stimulus time histograms , 2003, Brain Research.

[18]  S. Gandevia,et al.  The effect of electrical stimulation of the corticospinal tract on motor units of the human biceps brachii , 2002, The Journal of physiology.

[19]  R. Powers,et al.  Effects of large excitatory and inhibitory inputs on motoneuron discharge rate and probability. , 1999, Journal of neurophysiology.

[20]  R. Powers,et al.  Black box revisited: a technique for estimating postsynaptic potentials in neurons , 2005, Trends in Neurosciences.

[21]  F. Glocker,et al.  Nociceptive fingertip stimulation inhibits synergistic motoneuron pools in the human upper limb , 2000, Neurology.

[22]  K S Türker,et al.  Conditions for excitatory or inhibitory masseteric reflexes elicited by tooth pressure in man. , 1997, Archives of oral biology.

[23]  G. P. Moore,et al.  Statistical signs of synaptic interaction in neurons. , 1970, Biophysical journal.

[24]  Markus Kofler,et al.  Functional organization of exteroceptive inhibition following nociceptive electrical fingertip stimulation in humans , 2003, Clinical Neurophysiology.

[25]  M Manfredi,et al.  Silent period in upper limb muscles after noxious cutaneous stimulation in man. , 1997, Electroencephalography and clinical neurophysiology.

[26]  G. Baumgartner,et al.  The effect of nociceptive cutaneous stimuli on human motoneurons. , 1973, Brain : a journal of neurology.

[27]  K S Türker,et al.  Estimation of postsynaptic potentials in rat hypoglossal motoneurones: insights for human work , 2003, The Journal of physiology.

[28]  J. Shefner,et al.  Relationship between stimulus strength and the cutaneous silent period , 1993, Muscle & nerve.

[29]  M. Gorassini,et al.  Changes in sensory-evoked synaptic activation of motoneurons after spinal cord injury in man. , 2008, Brain : a journal of neurology.

[30]  Kemal S Türker,et al.  A method for quantifying reflex responses from intra-muscular and surface electromyogram , 2003, Journal of Neuroscience Methods.

[31]  K. Türker,et al.  Tendon tap induces a single long-lasting excitatory reflex in the motoneurons of human soleus muscle , 1997, Experimental Brain Research.

[32]  M. Floeter Cutaneous silent periods , 2003, Muscle & nerve.

[33]  J. Rothwell,et al.  A sound-evoked vestibulomasseteric reflex in healthy humans. , 2005, Journal of neurophysiology.

[34]  J. Stephens,et al.  Changes in the recruitment threshold of motor units produced by cutaneous stimulation in man. , 1981, The Journal of physiology.

[35]  E E Fetz,et al.  Relation between shapes of post‐synaptic potentials and changes in firing probability of cat motoneurones , 1983, The Journal of physiology.

[36]  M. Magistris,et al.  Cutaneous silent period in carpal tunnel syndrome , 2006, Muscle & nerve.

[37]  S. Pullman,et al.  Silent period induced by cutaneous stimulation. , 1991, Electroencephalography and clinical neurophysiology.

[38]  A. Leis Cutaneous silent period , 1998, Muscle & nerve.

[39]  J. Valls-Solé,et al.  The effect of a prepulse stimulus on the EMG rebound following the cutaneous silent period , 2009, The Journal of physiology.

[40]  André Mouraux,et al.  EEG and laser stimulation as tools for pain research. , 2005, Current opinion in investigational drugs.

[41]  G. Cruccu,et al.  Cutaneous silent period in hand muscle is evoked by laser stimulation of the palm, but not the hand dorsum , 2004, Muscle & nerve.

[42]  P H Ellaway,et al.  Cumulative sum technique and its application to the analysis of peristimulus time histograms. , 1978, Electroencephalography and clinical neurophysiology.