Inhibition of biceps brachii muscle motor area by painful heat stimulation of the skin

• Published in: Experimental brain research Vol. 139; no. 2; pp. 168 - 172
• Main Authors: VALERIANI, Massimiliano, RESTUCCIA, Domenico, DI LAZZARO, Vincenzo, OLIVIERO, Antonio, LE PERA, Domenica, PROFICE, Paolo, SATURNO, Eleonora, TONALI, Pietro
• Format: Journal Article
• Language: English
• Published: Berlin Springer 01-07-2001; Springer Nature B.V
• Subjects: Adult; Arm; Arm - radiation effects; Axons; Biological and medical sciences; Brain - physiopathology; Carbon dioxide; Cerebral cortex; Conditioning (Psychology); Cortex (motor); Electrical stimuli; Evoked Potentials, Motor - physiology; Excitability; Female; Fundamental and applied biological sciences. Psychology; Hand; Hand - radiation effects; Hot Temperature; Humans; Lasers; Magnetic fields; Male; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Motor evoked potentials; Muscle, Skeletal - physiopathology; Neural Inhibition - physiology; Pain - physiopathology; Pain perception; Pyramidal cells; Pyramidal tracts; Skin; Transcranial magnetic stimulation; Vertebrates: nervous system and sense organs; Human; Noxious stimulus; Motor pathway; Electrical stimulus; Central nervous system; Striated muscle; Motor control; Sensorimotor coordination; Motor cortex; Biceps brachii muscle; Magnetic stimulus; Skin; Motor evoked potential; Inhibition; Pyramidal neuron; Brain (vertebrata)
• ISSN: 0014-4819; 1432-1106
• DOI: 10.1007/s002210100753

ract This study aimed to evaluate whether painful cutaneous stimuli can affect specifically the excitability of the arm proximal muscle motor area. The motor evoked potentials (MEPs), recorded from the right biceps brachii muscle after either transcranial magnetic or electrical anodal stimulation of the left primary motor (MI) cortex, were conditioned by painful CO2 laser stimuli delivered either on the right hand dorsum or on the lateral surface of the right arm. Painful CO2 laser stimuli delivered on the hand skin reduced significantly the amplitude of MEPs evoked by the transcranial magnetic stimulation of the contralateral MI area, while the MEP amplitude was not significantly modified by CO2 laser pulses delivered on the arm skin. The inhibitory effect followed the arrival of the nociceptive inputs to the cerebral cortex. The amplitude of MEPs evoked by anodal electrical stimulation of the motor cortex was not decreased by conditioning painful stimuli delivered on the hand dorsum. Since the magnetic stimulation led to transynaptic activation of pyramidal neurons, while the anodal stimulation activated directly corticospinal axons, our findings suggest that CO2 laser pulses delivered on the hand are able to inhibit the arm proximal muscle motor area.