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The Journal of Neuroscience, March 29, 2006, 26(13):3505-3513; doi:10.1523/JNEUROSCI.5160-05.2006
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Behavioral/Systems/Cognitive
Kinematic and Electromyographic Study of the Nociceptive Withdrawal Reflex in the Upper Limbs during Rest and Movement
Mariano Serrao,1,2 Francesco Pierelli,2,5 Romildo Don,3 Alberto Ranavolo,3 Angelo Cacchio,3 Antonio Currà,4 Giorgio Sandrini,6 Massimo Frascarelli,3 andValter Santilli3 1Department of Neurology and Otolaryngology, 2Rehabilitation Unit, Polo Pontino-Istituto Chirurgico Ortopedíco Traumatologico, 3Department of Physical Medicine and Rehabilitation, Movement Analysis Laboratory, and 4Department of Neurological Sciences, Santa Maria Goretti Hospital, Latina, La Sapienza University of Rome, 00185 Rome, Italy, 5IRCCS Neuromed, 86077 Pozzilli, Italy, and 6Department of Neurological Sciences, Istituto di Ricovero e Cura a Carattere Scientifico C. Mondino Foundation, University of Pavia, 27100 Pavia, Italy
Correspondence should be addressed to Dr. Mariano Serrao, Department of Neurology and Otolaryngology, La Sapienza University of Rome, Viale dell'Università 30, 00185 Rome, Italy. Email: jackmarian{at}mclink.it
This study set out to evaluate nociceptive withdrawal reflex (NWR) excitability and the corresponding mechanical response in the upper limbs during rest and movement. We used a three-dimensional motion analysis system and a surface EMG system to record, in 10 healthy subjects, the NWR in eight upper limb muscles and the corresponding mechanical response in two experimental conditions: rest and movement (reaching for, picking up, and moving a cylinder). The NWR was elicited through stimulation of the index finger with trains of pulses delivered at multiples of the pain threshold (PT). We correlated movement types (reach-to-grasp, grasp-and-lift), movement phases (acceleration, deceleration), and muscle activity types (shortening, lengthening, isometric) with the presence/absence of the NWR (reflex-muscle pattern), with NWR size values, and with the mechanical responses.
At rest, when the stimulus was delivered at 4x PT, the NWR was present, in all muscles, in >90% of trials, and the mechanical response consisted of wrist adduction, elbow flexion, and shoulder anteflexion. At this stimulus intensity, during movement, the reflex-muscle pattern, reflex size, and mechanical responses were closely modulated by movement type and phase and by muscle activity type. We did not find, during movement, significant correlations with the level of EMG background activity.
Our findings suggest that a complex functional adaptation of the spinal cord plays a role in modulating the NWR in the transition from rest to movement and during voluntary arm movement freely performed in three-dimensional space. Study of the upper limb NWR may provide a window onto the spinal neural control mechanisms operating during movement.
Key words: nociceptive withdrawal reflex; spinal reflexes; painful stimulation; movement analysis; central pattern generator; spinal interneurons; state dependent; movement phase
Received Aug. 9, 2005; revised Jan. 29, 2006; accepted Jan. 31, 2006.
Correspondence should be addressed to Dr. Mariano Serrao, Department of Neurology and Otolaryngology, La Sapienza University of Rome, Viale dell'Università 30, 00185 Rome, Italy. Email: jackmarian{at}mclink.it
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