TY - JOUR
T1 - Inhibition of the human primary motor area by painful heat stimulation of the skin
AU - Valeriani, Massimiliano
AU - Restuccia, Domenico
AU - Di Lazzaro, Vincenzo
AU - Oliviero, Antonio
AU - Profice, Paolo
AU - Le Pera, Domenica
AU - Saturno, Eleonora
AU - Tonali, Pietro
PY - 1999/8/1
Y1 - 1999/8/1
N2 - Objective: To prove whether painful cutaneous stimuli can affect specifically the motor cortex excitability. Methods: The electromyographic (EMG) responses, recorded from the first dorsal interosseous muscle after either transcranial magnetic or electric anodal stimulation of the primary motor (MI) cortex, was conditioned by both painful and non-painful CO2 laser stimuli delivered on the hand skin. Results: Painful CO2 laser stimuli reduced the amplitude of the EMG responses evoked by the transcranial magnetic stimulation of both the contralateral and ipsilateral MI areas. This inhibitory effect followed the arrival of the nociceptive inputs to cerebral cortex. Instead, the EMG response amplitude was not significantly modified either when it was evoked by the motor cortex anodal stimulation or when nonpainful CO2 laser pulses were used as conditioning stimuli. Conclusions: Since the magnetic stimulation leads to transynaptic activation of pyramidal neurons, while the anodal stimulation activates directly cortico-spinal axons, the differential effect of the noxious stimuli on the EMG responses evoked by the two motor cortex stimulation techniques suggests that the observed inhibitory effect has a cortical origin. The bilateral cortical representation of pain explains why the painful CO2 laser stimuli showed a conditioning effect on MI area of both hemispheres. Non-painful CO2 laser pulses did not produce any effect, thus suggesting that the reduction of the MI excitability was specifically due to the activation of nociceptive afferents.
AB - Objective: To prove whether painful cutaneous stimuli can affect specifically the motor cortex excitability. Methods: The electromyographic (EMG) responses, recorded from the first dorsal interosseous muscle after either transcranial magnetic or electric anodal stimulation of the primary motor (MI) cortex, was conditioned by both painful and non-painful CO2 laser stimuli delivered on the hand skin. Results: Painful CO2 laser stimuli reduced the amplitude of the EMG responses evoked by the transcranial magnetic stimulation of both the contralateral and ipsilateral MI areas. This inhibitory effect followed the arrival of the nociceptive inputs to cerebral cortex. Instead, the EMG response amplitude was not significantly modified either when it was evoked by the motor cortex anodal stimulation or when nonpainful CO2 laser pulses were used as conditioning stimuli. Conclusions: Since the magnetic stimulation leads to transynaptic activation of pyramidal neurons, while the anodal stimulation activates directly cortico-spinal axons, the differential effect of the noxious stimuli on the EMG responses evoked by the two motor cortex stimulation techniques suggests that the observed inhibitory effect has a cortical origin. The bilateral cortical representation of pain explains why the painful CO2 laser stimuli showed a conditioning effect on MI area of both hemispheres. Non-painful CO2 laser pulses did not produce any effect, thus suggesting that the reduction of the MI excitability was specifically due to the activation of nociceptive afferents.
KW - Human brain
KW - Inhibition
KW - Laser EPs
KW - Motor Cortex
KW - Pain
KW - SII area
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U2 - 10.1016/S1388-2457(99)00075-9
DO - 10.1016/S1388-2457(99)00075-9
M3 - Article
C2 - 10454286
AN - SCOPUS:0032816598
VL - 110
SP - 1475
EP - 1480
JO - Clinical Neurophysiology
JF - Clinical Neurophysiology
SN - 1388-2457
IS - 8
ER -