Movements modulate cortical activities evoked by noxious stimulation Hiroki Nakata a,b, * , Koji Inui a , Toshiaki Wasaka a , Yohei Tamura a , Tuan Diep Tran a , Yunhai Qiu a,b , Xiaohong Wang a,b , Thi Binh Nguyen a,b , Ryusuke Kakigi a,b a Department of Integrative Physiology, National Institute for Physiological Sciences, Myodaiji, Okazaki 444-8585, Japan b Department of Physiological Sciences, School of life Sciences, The Graduate University for Advanced Studies, Hayama, Kanagawa, Japan Received 4 April 2003; received in revised form 6 September 2003; accepted 1 October 2003 Abstract To evaluate the effects of movement on cortical activities evoked by noxious stimulation, we recorded magnetoencephalography following noxious YAG laser stimulation applied to the dorsum of the left hand in normal volunteers. Results of the present study can be summarized as follows: (1) active movement of the hand ipsilateral to the side of noxious stimulation resulted in significant attenuation of both primary and secondary somatosensory cortices (SI and SII) in the hemisphere contralateral to the stimulated hand (cSI and cSII). Activity in the hemisphere ipsilateral to the side of stimulation (iSII) was not affected. (2) Active movement of the hand contralateral to the side of noxious stimulation resulted in significant attenuation of cSII. Activity in cSI and iSII was not affected. (3) Passive movement of the hand ipsilateral to the side of noxious stimulation resulted in significant attenuation of cSI. Activity in cSII and iSII was not affected. (4) Visual analogue scale (VAS) changes showed a similar pattern to the amplitude changes of cSII. These results suggest that activities in three regions are modulated by movements differently. Inhibition in cSI was considered to be mainly due to an interaction in SI by the signals ascending from the stimulated and movement hand. Inhibition in cSII was considered to be mainly due to particular brain activities relating to motor execution and/or movement execution associated with a specific attention effect. In addition, since VAS changes showed a similar relationship with the amplitude changes of cSII, cSII may play a role in pain perception. q 2003 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved. Keywords: Noxious stimulation; Movement; Pain; YAG laser; Magnetoencephalography 1. Introduction Subjective pain sensations can be easily influenced by mental condition such as attention and arousal. In addition, peripheral inputs attenuate subjective pain feeling (see Kakigi and Watanabe, 1996). Movements of the limbs should also relieve pain, since we move our limbs when they receive a painful sensation; for example waving our hand unconsciously in response to painful stimuli. Kakigi and Shibasaki (1992) and Kakigi et al. (1993) reported that somatosensory evoked potentials (SEPs) following painful CO 2 laser stimulation were markedly attenuated by move- ments of the limbs where the laser stimulation was applied. However, because there was no follow-up study, the underlying mechanisms of pain relief by movement have not been elucidated. Laser-evoked pain-related SEPs (LEPs) have been studied to evaluate the mechanism of pain perception in both basic (see Arendt-Nielsen et al., 1999; Bromm and Lorenz, 1998; Chen et al., 1998a,b; Treede et al., 1999, 2000) and clinical research (see Kakigi et al., 2000). Evoked potentials obtained by averaging electroencephalography (EEG) have a high temporal resolution in a millisecond order, but their spatial resolution is low because of the effect of the electrical conductivity of cerebrospinal fluid, skull and skin, and so generator sources for each recognizable component, have not been clarified in detail. In contrast, magnetoencephalography (MEG) has several theoretical advantages in localizing brain activities. Recent MEG studies have clarified that the primary somatosensory cortex (SI) contralateral to the stimulation and bilateral secondary somatosensory corticies (SII) were activated within 200 ms following noxious stimulation applied to the upper limbs 0304-3959/$20.00 q 2003 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.pain.2003.10.001 Pain 107 (2004) 91–98 www.elsevier.com/locate/pain * Corresponding author. Address: Department of Integrative Physiology, National Institute for Physiological Sciences, Myodaiji, Okazaki 444-8585, Japan. Tel.: þ 81-564-55-7769; fax: þ81-564-52-7913. E-mail address: nakata@nips.ac.jp (H. Nakata).