Functional organization of exteroceptive inhibition following nociceptive electrical fingertip stimulation in humans. 2003

Markus Kofler
Department of Neurology, Hospital Hochzirl, A-6170, Zirl, Austria. markus.kofler@uibk.ac.at

OBJECTIVE To investigate the functional organization of inhibitory spinal reflexes mediated by cutaneous afferents (=cutaneous silent periods, CSPs) in order to assess differential strategies used by the human spinal cord to inhibit movement in upper limb muscles within the same myotome. METHODS Twenty healthy subjects underwent assessment of the effect of electrical finger-tip stimulation with different intensities on voluntarily contracting hand muscles. The rectified and averaged electromyogram (EMG) was recorded with surface electrodes placed over abductor pollicis brevis (APB), abductor digiti minimi (ADM), and first dorsal interosseous (FDI) muscles following recurrent digit II and digit V stimulation. RESULTS Finger-tip stimulation resulted in a series of inhibitory and excitatory EMG responses in all 3 hand muscles. Stimulus intensity exerted a significant influence on various CSP parameters (probability, onset and end latency, duration, index of suppression). CSPs were most pronounced in APB following digit II and, somewhat less, following digit V stimulation. FDI and ADM differed in CSP onset latency following digit II stimulation, and in the overall amount of suppression following digit V stimulation, despite being supplied by the same nerve and the same myotome. Excitatory long-loop reflexes seemed to be suppressed by increasing stimulus intensities, yet they interfered with CSPs, even when using noxious stimulation, in FDI following digit II stimulation, and in both ADM and FDI following digit V stimulation. CONCLUSIONS The findings are consistent with the presence of an inhibitory neural circuitry within the human spinal cord which can rapidly restrain distinct muscle synergies. Neurophysiology indicates a more functional - task-related - organization of protective reflexes in the human upper extremity, rather than a merely metameric - anatomically based - order of activation of this neuronal circuitry.

UI MeSH Term Description Entries
D008297 Male Males
D009433 Neural Inhibition The function of opposing or restraining the excitation of neurons or their target excitable cells. Inhibition, Neural
D010146 Pain An unpleasant sensation induced by noxious stimuli which are detected by NERVE ENDINGS of NOCICEPTIVE NEURONS. Suffering, Physical,Ache,Pain, Burning,Pain, Crushing,Pain, Migratory,Pain, Radiating,Pain, Splitting,Aches,Burning Pain,Burning Pains,Crushing Pain,Crushing Pains,Migratory Pain,Migratory Pains,Pains, Burning,Pains, Crushing,Pains, Migratory,Pains, Radiating,Pains, Splitting,Physical Suffering,Physical Sufferings,Radiating Pain,Radiating Pains,Splitting Pain,Splitting Pains,Sufferings, Physical
D010812 Physical Stimulation Act of eliciting a response from a person or organism through physical contact. Stimulation, Physical,Physical Stimulations,Stimulations, Physical
D011336 Probability The study of chance processes or the relative frequency characterizing a chance process. Probabilities
D011930 Reaction Time The time from the onset of a stimulus until a response is observed. Response Latency,Response Speed,Response Time,Latency, Response,Reaction Times,Response Latencies,Response Times,Speed, Response,Speeds, Response
D012018 Reflex An involuntary movement or exercise of function in a part, excited in response to a stimulus applied to the periphery and transmitted to the brain or spinal cord.
D004558 Electric Stimulation Use of electric potential or currents to elicit biological responses. Stimulation, Electric,Electrical Stimulation,Electric Stimulations,Electrical Stimulations,Stimulation, Electrical,Stimulations, Electric,Stimulations, Electrical
D004561 Transcutaneous Electric Nerve Stimulation The use of specifically placed small electrodes to deliver electrical impulses across the SKIN to relieve PAIN. It is used less frequently to produce ANESTHESIA. Analgesic Cutaneous Electrostimulation,Electric Stimulation, Transcutaneous,Electroanalgesia,Percutaneous Electric Nerve Stimulation,TENS,Transdermal Electrostimulation,Electrical Stimulation, Transcutaneous,Percutaneous Electrical Nerve Stimulation,Percutaneous Electrical Neuromodulation,Percutaneous Neuromodulation Therapy,Transcutaneous Electrical Nerve Stimulation,Transcutaneous Nerve Stimulation,Cutaneous Electrostimulation, Analgesic,Electrical Neuromodulation, Percutaneous,Electrical Neuromodulations, Percutaneous,Electroanalgesias,Electrostimulation, Analgesic Cutaneous,Electrostimulation, Transdermal,Nerve Stimulation, Transcutaneous,Neuromodulation Therapy, Percutaneous,Neuromodulation, Percutaneous Electrical,Neuromodulations, Percutaneous Electrical,Percutaneous Electrical Neuromodulations,Percutaneous Neuromodulation Therapies,Stimulation, Transcutaneous Electric,Stimulation, Transcutaneous Nerve,Therapy, Percutaneous Neuromodulation,Transcutaneous Electric Stimulation,Transcutaneous Electrical Stimulation
D004576 Electromyography Recording of the changes in electric potential of muscle by means of surface or needle electrodes. Electromyogram,Surface Electromyography,Electromyograms,Electromyographies,Electromyographies, Surface,Electromyography, Surface,Surface Electromyographies

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