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Analysis of the source in the sensory area during self-paced finger movements
International Congress Series 1232 (2002) 473 – 478
Analysis of the source in the sensory area during self-paced finger movements M. Niimi *, T. Ohira, M. Ochiai, Y. Kaneko, T. Kawase Department of Neurosurgery, Keio University, 35 Shinanomachi, Shinjuku, Tokyo, 160-8582 Japan
Abstract The movement-related cortical fields (MRCFs) accompanying index finger movements and somatosensory-evoked fields (SEFs) were investigated in 10 subjects. Movement-evoked field (MEFI) was observed in all of the subjects. The dipole of MEFI was directed posteriorly and was located in the postcentral gyrus of the hemisphere contralateral to the movement. The SEFs showed three major components: N20m, P30m and P60m. The direction of the MEFI dipole was similar to that of P30m and P60m. Based on the distribution of the dipole locations, MEFI was similar to P60m and different from P30m. The mean location of the MEFI dipole was more posterior and medial than the dipole position of P30m and P60m. It suggests that MEFI was generated by the higher sensory area. D 2002 Published by Elsevier Science B.V. Keywords: Magnetoencephalography; Motor-evoked field; Somatosensory-evoked field; Movement-related cortical field
1. Introduction The component of the movement-evoked field (MEF) defined by Kristeva [4] after finger movement is large and stable. The dipole was found to be directed posteriorly, but it was unclear whether it was located in the somatosensory area or the motor area. In this study, we examined the source of MEF by using a 160-channel SQUID neuromagnetometer, and the location of the dipole was precisely superimposed on the MRI images. We compared MEF with SEF, whose source was clear.
*
Corresponding author.
0531-5131/02 D 2002 Published by Elsevier Science B.V. PII: S 0 5 3 1 - 5 1 3 1 ( 0 1 ) 0 0 7 8 3 - X
474
M. Niimi et al. / International Congress Series 1232 (2002) 473–478
2. Subjects Ten normal subjects (five men and five women; mean age 41.4 years, range 24– 71 years) participated in the study.
3. Methods 3.1. Movement-related cortical field (MRCF) recording The subject was asked to briskly extend the right or left index finger from complete muscle relaxation. Each movement was repeated voluntarily at irregular self-paced intervals exceeding 5 ms. A recording session consisted of 200 trials of the same movement, and two sessions were carried out. A light sensor generated a trigger pulse at the beginning of each movement. A 160-channel SQUID neuromagnetometer that covered the entire scalp recorded the brain’s magnetic fields. Responses were digitized at a sampling rate of 500 Hz. The analysis window extended from 1500 ms before the onset of the light sensor trigger to 1000 ms after it. 3.2. Somatosensory-evoked field (SEF) recording The median nerve was stimulated with an electrical square wave of 2 Hz. One session consisted of 400 stimulations, and two sessions were carried out. 3.3. Head coordination The negative y-axis passed through the nasion (postero-anterior direction), the positive x-axis through the left preauricular point (medio-lateral direction) and the z-axis through the top of the head (infero-superior direction).
Fig. 1. The waveforms of MEFI.
M. Niimi et al. / International Congress Series 1232 (2002) 473–478
Fig. 2. The waveforms of SEF.
Fig. 3. Schematic sagittal view diagrams indicating the position of MEFI and SEF.
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M. Niimi et al. / International Congress Series 1232 (2002) 473–478
Fig. 4. The mean locations of MEFI and SEF.
3.4. Analysis The dipole was calculated by a single equivalent current dipole (ECD) method and the dipole location was precisely superimposed on the MRI images.
4. Results The waveforms of MEF are shown in Fig. 1. The readiness field, motor field and MEF were identified. MEFI was observed in all of the subjects. The peak latency of MEFI was 40.8F6.8 ms after the light sensor was triggered. The dipole was directed posteriorly. It was located in a dispersed manner in the postcentral gyrus of the hemisphere contralateral to the movement in seven subjects and in the central sulcus in three subjects. Sagittal view schematic diagrams indicating the position of the MEFI of all subjects are shown (Fig. 3). The waveforms of SEF are shown in Fig. 2. There are three peaks and their latency was 19.1F0.9 (meanFS.D.), 26.8F2.4 and 54.1F15.7 ms after stimulation. The direction of the dipole was anterior at the first peak and posterior at the second and third peak. The dipoles of the first peak (N20m) were located on the posterior wall of the central sulcus. The dipoles of the second peak (P30m) were located in the central sulcus and more anterior than the first peak. The dipoles of the third peak (P60m) were dispersed in the central sulcus and the postcentral gyrus. Sagittal view schematic diagrams indicating the position of the SEF dipoles are shown in Fig. 3 and the mean locations of MEFI and SEF are shown in Fig. 4.
5. Discussion There have been many arguments concerning the location of MEFI. In some previous reports, its location has been described as mainly in the sensory area [1,4 – 6], and in
M. Niimi et al. / International Congress Series 1232 (2002) 473–478
477
Fig. 5. The distances of the dipole locations of MEFI from central sulcus.
others, as mainly in the motor area [2,3,7], but only three reports used MRI images [3,5,7] on which the dipole locations were superimposed. The single dipole analysis for MEFI revealed the generator to be in the posterior bank of the central sulcus of the hemisphere contralateral to the side of the movement [1,6]. Kristeva et al. [4] hypothesized that MEFI is the initial input to the postcentral gyrus (primary sensory cortex, S1) from muscle afferents due to the finger movement. The dipole location of MEFI suggested that it could reflect reafferent activity from the periphery to the somatosensory cortex and the precentral sources may remain active during this period [1,6]. MEFI corresponds to P90 in MRCP [6]. In previous MEG studies, the origin of the N20m was speculated to be in the posterior wall of the central sulcus, area 3b [9]. N20m corresponds to N20 as reported in previous EEG studies and P30m corresponds to P30 [9]. P60m has been found to have a dipole in an antero-posterior direction [9 –11]. The present study indicated that the dipole sources corresponding to P60m are located in the somatosensory cortex of S1 [8]. In this study, we compared MEFI with SEF and found that the direction of the MEFI dipole was similar to that of P30m and P60m. The distribution of the dipole locations indicated that MEFI was similar to P60m and different from P30m. The mean of the MEFI dipole location was more posterior and medial than the dipole position of P30m and P60m (Fig. 4). The distances of the dipole locations of MEFI from the central sulcus are shown in Fig. 5. The mean distance of the dipole locations of MEFI from the central sulcus was 6.5 mm. Based on the findings in this study, the source of MEFI is the sensory area. However, MEFI was different from N20 and P30. Most of locations of MEFI were in the posterior portion of postcentral gyrus, so it suggests that MEFI was generated by the higher sensory area. On the other hand, some dipoles of MEFI were located in the anterior portion of the postcentral gyrus, so the activity of precentral sources may influence MEFI. References [1] M. Hoshiyama, R. Kakigi, et al., Identification of motor and sensory brain activities during unilateral finger movement, Exp. Brain Res. 115 (1997) 6 – 14. [2] T. Nagamine, et al., Movement-related slow cortical magnetic fields and changes of spontaneous MEG- and EEG-brain rhythms, Electroencephalogr. Clin. Neurophysiol. 99 (1996) 276 – 286. [3] O. Ganslandt, et al., Functional neuronavigation with magnetoencephalography: outcome in 50 patients with lesions around the motor cortex, J. Neurosurg. 91 (1999) 73 – 79.
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M. Niimi et al. / International Congress Series 1232 (2002) 473–478
[4] R. Kristeva, et al., Neuromagnetic fields accompanying unilateral and bilateral voluntary movements, Electroencephalogr. Clin. Neurophysiol. 81 (1991) 284 – 298. [5] R. Kristeva, et al., Neuromagnetic fields of the brain evoked by voluntary movement and electrical stimulation of the index finger, Brain Res. 682 (1995) 22 – 28. [6] D. Cheyne, H. Weinberg, Neuromagnetic fields accompanying unilateral finger movements: pre-movement and movement-evoked fields, Exp. Brain Res. 78 (1989) 604 – 612. [7] T. Weiss, W. Miltner, Reliability of dipole location for the movement-evoked field component MEFI, Int. J. Neurosci. 91 (1 – 2) (1997) 123 – 132. [8] H. Ishibashi, et al., Differential interaction of somatosensory inputs in the human primary sensory cortex: a magnetoencephalographic study, Clin. Neurophysiol. 111 (2000) 1095 – 1102. [9] T. Kawamura, N. Nakasato, et al., Neuromagnetic evidence of pre- and post-central cortical sources of somatosensory evoked responses, Electroencephalogr. Clin. Neurophysiol. 100 (1996) 44 – 50. [10] T. Morioka, et al., Presurgical three-dimensional magnetic source imaging of the somatosensory cortex in a patient with a peri-Rolandic lesion: technical note, Neurosurgery 34 (1994) 930 – 933. [11] H. Wisktrom, et al., Effect of interstimulus interval on somatosensory evoked magnetic fields (SEFs), Electroencephalogr. Clin. Neurophysiol. 100 (1996) 479 – 487.
Analysis of the source in the sensory area during self-paced finger movements M. Niimi *, T. Ohira, M. Ochiai, Y. Kaneko, T. Kawase Department of Neurosurgery, Keio University, 35 Shinanomachi, Shinjuku, Tokyo, 160-8582 Japan
Abstract The movement-related cortical fields (MRCFs) accompanying index finger movements and somatosensory-evoked fields (SEFs) were investigated in 10 subjects. Movement-evoked field (MEFI) was observed in all of the subjects. The dipole of MEFI was directed posteriorly and was located in the postcentral gyrus of the hemisphere contralateral to the movement. The SEFs showed three major components: N20m, P30m and P60m. The direction of the MEFI dipole was similar to that of P30m and P60m. Based on the distribution of the dipole locations, MEFI was similar to P60m and different from P30m. The mean location of the MEFI dipole was more posterior and medial than the dipole position of P30m and P60m. It suggests that MEFI was generated by the higher sensory area. D 2002 Published by Elsevier Science B.V. Keywords: Magnetoencephalography; Motor-evoked field; Somatosensory-evoked field; Movement-related cortical field
1. Introduction The component of the movement-evoked field (MEF) defined by Kristeva [4] after finger movement is large and stable. The dipole was found to be directed posteriorly, but it was unclear whether it was located in the somatosensory area or the motor area. In this study, we examined the source of MEF by using a 160-channel SQUID neuromagnetometer, and the location of the dipole was precisely superimposed on the MRI images. We compared MEF with SEF, whose source was clear.
*
Corresponding author.
0531-5131/02 D 2002 Published by Elsevier Science B.V. PII: S 0 5 3 1 - 5 1 3 1 ( 0 1 ) 0 0 7 8 3 - X
474
M. Niimi et al. / International Congress Series 1232 (2002) 473–478
2. Subjects Ten normal subjects (five men and five women; mean age 41.4 years, range 24– 71 years) participated in the study.
3. Methods 3.1. Movement-related cortical field (MRCF) recording The subject was asked to briskly extend the right or left index finger from complete muscle relaxation. Each movement was repeated voluntarily at irregular self-paced intervals exceeding 5 ms. A recording session consisted of 200 trials of the same movement, and two sessions were carried out. A light sensor generated a trigger pulse at the beginning of each movement. A 160-channel SQUID neuromagnetometer that covered the entire scalp recorded the brain’s magnetic fields. Responses were digitized at a sampling rate of 500 Hz. The analysis window extended from 1500 ms before the onset of the light sensor trigger to 1000 ms after it. 3.2. Somatosensory-evoked field (SEF) recording The median nerve was stimulated with an electrical square wave of 2 Hz. One session consisted of 400 stimulations, and two sessions were carried out. 3.3. Head coordination The negative y-axis passed through the nasion (postero-anterior direction), the positive x-axis through the left preauricular point (medio-lateral direction) and the z-axis through the top of the head (infero-superior direction).
Fig. 1. The waveforms of MEFI.
M. Niimi et al. / International Congress Series 1232 (2002) 473–478
Fig. 2. The waveforms of SEF.
Fig. 3. Schematic sagittal view diagrams indicating the position of MEFI and SEF.
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476
M. Niimi et al. / International Congress Series 1232 (2002) 473–478
Fig. 4. The mean locations of MEFI and SEF.
3.4. Analysis The dipole was calculated by a single equivalent current dipole (ECD) method and the dipole location was precisely superimposed on the MRI images.
4. Results The waveforms of MEF are shown in Fig. 1. The readiness field, motor field and MEF were identified. MEFI was observed in all of the subjects. The peak latency of MEFI was 40.8F6.8 ms after the light sensor was triggered. The dipole was directed posteriorly. It was located in a dispersed manner in the postcentral gyrus of the hemisphere contralateral to the movement in seven subjects and in the central sulcus in three subjects. Sagittal view schematic diagrams indicating the position of the MEFI of all subjects are shown (Fig. 3). The waveforms of SEF are shown in Fig. 2. There are three peaks and their latency was 19.1F0.9 (meanFS.D.), 26.8F2.4 and 54.1F15.7 ms after stimulation. The direction of the dipole was anterior at the first peak and posterior at the second and third peak. The dipoles of the first peak (N20m) were located on the posterior wall of the central sulcus. The dipoles of the second peak (P30m) were located in the central sulcus and more anterior than the first peak. The dipoles of the third peak (P60m) were dispersed in the central sulcus and the postcentral gyrus. Sagittal view schematic diagrams indicating the position of the SEF dipoles are shown in Fig. 3 and the mean locations of MEFI and SEF are shown in Fig. 4.
5. Discussion There have been many arguments concerning the location of MEFI. In some previous reports, its location has been described as mainly in the sensory area [1,4 – 6], and in
M. Niimi et al. / International Congress Series 1232 (2002) 473–478
477
Fig. 5. The distances of the dipole locations of MEFI from central sulcus.
others, as mainly in the motor area [2,3,7], but only three reports used MRI images [3,5,7] on which the dipole locations were superimposed. The single dipole analysis for MEFI revealed the generator to be in the posterior bank of the central sulcus of the hemisphere contralateral to the side of the movement [1,6]. Kristeva et al. [4] hypothesized that MEFI is the initial input to the postcentral gyrus (primary sensory cortex, S1) from muscle afferents due to the finger movement. The dipole location of MEFI suggested that it could reflect reafferent activity from the periphery to the somatosensory cortex and the precentral sources may remain active during this period [1,6]. MEFI corresponds to P90 in MRCP [6]. In previous MEG studies, the origin of the N20m was speculated to be in the posterior wall of the central sulcus, area 3b [9]. N20m corresponds to N20 as reported in previous EEG studies and P30m corresponds to P30 [9]. P60m has been found to have a dipole in an antero-posterior direction [9 –11]. The present study indicated that the dipole sources corresponding to P60m are located in the somatosensory cortex of S1 [8]. In this study, we compared MEFI with SEF and found that the direction of the MEFI dipole was similar to that of P30m and P60m. The distribution of the dipole locations indicated that MEFI was similar to P60m and different from P30m. The mean of the MEFI dipole location was more posterior and medial than the dipole position of P30m and P60m (Fig. 4). The distances of the dipole locations of MEFI from the central sulcus are shown in Fig. 5. The mean distance of the dipole locations of MEFI from the central sulcus was 6.5 mm. Based on the findings in this study, the source of MEFI is the sensory area. However, MEFI was different from N20 and P30. Most of locations of MEFI were in the posterior portion of postcentral gyrus, so it suggests that MEFI was generated by the higher sensory area. On the other hand, some dipoles of MEFI were located in the anterior portion of the postcentral gyrus, so the activity of precentral sources may influence MEFI. References [1] M. Hoshiyama, R. Kakigi, et al., Identification of motor and sensory brain activities during unilateral finger movement, Exp. Brain Res. 115 (1997) 6 – 14. [2] T. Nagamine, et al., Movement-related slow cortical magnetic fields and changes of spontaneous MEG- and EEG-brain rhythms, Electroencephalogr. Clin. Neurophysiol. 99 (1996) 276 – 286. [3] O. Ganslandt, et al., Functional neuronavigation with magnetoencephalography: outcome in 50 patients with lesions around the motor cortex, J. Neurosurg. 91 (1999) 73 – 79.
478
M. Niimi et al. / International Congress Series 1232 (2002) 473–478
[4] R. Kristeva, et al., Neuromagnetic fields accompanying unilateral and bilateral voluntary movements, Electroencephalogr. Clin. Neurophysiol. 81 (1991) 284 – 298. [5] R. Kristeva, et al., Neuromagnetic fields of the brain evoked by voluntary movement and electrical stimulation of the index finger, Brain Res. 682 (1995) 22 – 28. [6] D. Cheyne, H. Weinberg, Neuromagnetic fields accompanying unilateral finger movements: pre-movement and movement-evoked fields, Exp. Brain Res. 78 (1989) 604 – 612. [7] T. Weiss, W. Miltner, Reliability of dipole location for the movement-evoked field component MEFI, Int. J. Neurosci. 91 (1 – 2) (1997) 123 – 132. [8] H. Ishibashi, et al., Differential interaction of somatosensory inputs in the human primary sensory cortex: a magnetoencephalographic study, Clin. Neurophysiol. 111 (2000) 1095 – 1102. [9] T. Kawamura, N. Nakasato, et al., Neuromagnetic evidence of pre- and post-central cortical sources of somatosensory evoked responses, Electroencephalogr. Clin. Neurophysiol. 100 (1996) 44 – 50. [10] T. Morioka, et al., Presurgical three-dimensional magnetic source imaging of the somatosensory cortex in a patient with a peri-Rolandic lesion: technical note, Neurosurgery 34 (1994) 930 – 933. [11] H. Wisktrom, et al., Effect of interstimulus interval on somatosensory evoked magnetic fields (SEFs), Electroencephalogr. Clin. Neurophysiol. 100 (1996) 479 – 487.