Institute of Development, Aging and Cancer, Tohoku University

About

Dept. Electromagnetic Neurophysiology

Professor Nobukazu NAKASATO
Associate Professor Kazutaka JIN
Senior Assistant Professor Yosuke KAKISAKA
Assistant Professor Mayu FUJIKAWA
Homepage of This Laboratory

INTRODUCTION

The Department of Electromagnetic Neurophysiology, founded in May 2010, is a research facility of the Smart Ageing International Research Center (SAIRC). Our mission is to investigate brain physiology through electromagnetic measurement and stimulation, to develop the electromagnetic tools for research and medicine, and to promote clinical applications of electromagnetic neurophysiology. Here we describe four representative methods of electromagnetic neurophysiology: electroencephalography (EEG), magnetoencephalography (MEG), electrical brain stimulation, and magnetic brain stimulation.

EEG

Brain neuronal currents can be measured electrically by EEG. EEG provides lots of information about normal brain function and abnormal activity related to disease. Scalp EEG is a common noninvasive technique, providing routine examinations for various types of brain diseases. However, the spatial resolution of scalp EEG is limited because of serious distortion effects caused by inhomogeneous head conductivity. For more accurate measurement of brain signals, intracranial electrodes can be used to perform corticography, brain surface EEG or electrocorticography (ECoG), and deep brain EEG or depth EEG. Intracranial EEG is indicated only for patients with specific diseases such as medically intractable epilepsy or brain tumors. However, intracranial EEG also provides unique opportunities to investigate human neurophysiology. Intracranial EEG can be measured intraoperatively, or extraoperatively using chronically implanted electrodes. Many opportunities to use intracranial EEG are available since Dr. Nobukazu Nakasato, Professor and Chairman of the Department of Electromagnetic Neurophysiology, heads the Department of Epileptology, Tohoku University Hospital.

MEG

Brain neuronal currents can be magnetically measured by MEG. However, the MEG signal is extremely weak in the order of fT (femto tesla = 10-15 tesla), so measurement requires a specially designed magnetically shielded room and high sensitivity magnetic sensors called a superconducting quantum interference device (SQUID). Recent developments of low temperature technology have enabled construction of helmet-shaped MEG systems with multichannel SQUID sensor arrays. Despite the large-scale equipment, MEG provides higher spatial resolution than scalp EEG since MEG suffers far lower distortion effects caused by inhomogeneous head conductivity. MEG research in Tohoku University started in 1987, and many articles have been published on brain mapping of somatosensory, auditory, gustatory, visual, and language functions. We have also accelerated the diagnostic application of MEG for epilepsy and ischemic brain diseases. Now we will embark new era of MEG, as Dr. Ryuta Kawashima, Director of SAIRC, introduced a new MEG system in March 2010 and Dr. Nobukazu Nakasato was appointed as the Chairman, Department of Electromagnetic Neurophysiology in May 2010.

ELECTRICAL BRAIN STIMULATION

The brain can be electrically stimulated directly during surgery (intraoperative cortical stimulation), or using chronically implanted intracranial electrodes (extraoperative cortical stimulation). Intracranial stimulation is exclusively limited to preoperative brain mapping for patients with specific diseases such as medically intractable epilepsy or malignant brain tumors. However, modern neuroscience has greatly developed with clinical experience, illustrated by the famous human brain mapping pioneered by Wilder Penfield and his colleagues.

MAGNETIC BRAIN STIMULATION

The brain can be stimulated magnetically by transcranial magnetic stimulation (TMS) using electrical coils on the head to generate a brief magnetic field which penetrates the cerebral cortex. TMS is usually coupled with electromyography response detection to assess cortical excitability based on the threshold required to induce motor evoked potentials. TMS can be used for brain mapping, and neuromodulation therapy for treating depression or other neurological diseases.

HISTORY AND FUTURE

Dr. Koichi Motokawa, Ex-Chair of the Department of Physiology, and Ex-President of Tohoku University, started the pioneering research work of EEG here in Sendai before World War II. We are also proud of our pioneering work of MEG since 1987. Our new department aims to expand the previous concept of “electrophysiology” into “electromagnetophysiology.” Our facility welcomes highly motivated young researchers and physicians.

Fig.1
FIGURE 1. Facility for simultaneous recording of EEG and MEG (Kohnan Hospital, Sendai).
Fig.2
FIGURE 2. Combined analysis of scalp EEG and MEG to localize the source of epileptic spike discharges.
Fig.3
FIGURE 3. EMEG (EEG and MEG) Club meets weekly to discuss project protocols and to review relevant articles in the field of EEG and MEG research.
Fig.3
FIGURE 4. Example of language mapping using chronically implanted intracranial electrodes in a patient with medically intractable epilepsy (Tanji K, et al. 2005).

Publication

  1. Osawa SI, Iwasaki M, Suzuki H, Nakasato N, Tominaga T: Occult dual pathology in mesial temporal lobe epilepsy. Neurol Sci 2015
  2. Iwasaki M, Uematsu M, Hino-Fukuyo N, Osawa SI, Shimoda Y, Jin K, Nakasato N, Tominaga T: Clinical profiles for seizure remission and developmental gains after total corpus callosotomy. Brain Dev 2015 (in press)
  3. Fujikawa M, Kishimoto Y, Kakisaka Y, Jin K, Kato K, Iwasaki M, Nakasato N: Obsessive-compulsive behavior induced by levetiracetam. J Child Neurol 30: 942-944, 2015
  4. Iwasaki M, Uematsu M, Hino-Fukuyo N, Osawa S, Shimoda Y, Jin K, Nakasato N, Tominaga T: Clinical profiles for seizure remission and developmental gains after total corpus callosotomy. Brain Dev 2015 (in press).
  5. Kakisaka Y, Jin K, Kato K, Iwasaki M, Nakasato N: Seizure freedom after lamotorigine rash: a peculiar phenomenon in epilepsy. Int Med 53: 2521-2522, 2014
  6. Kato K, Jin K, Itabashi H, Iwasaki M, Kakisaka Y, Aoki M, Nakasato N: Earlier tachycardia onset in right than left mesial temporal lobe seizures. Neurology 83: 1232-1236, 2014
  7. Usubuchi H, Kawase T, Kanno A, Yahata I, Miyazaki H, Nakasato N, Kawashima R, Katori Y: Effects of contralateral noise on the 20-Hz auditory steady state response - magnetoencephalography study. PLoS ONE 9(6): e99457, 2014
  8. Itabashi H, Jin K, Iwasaki M, Okumura E, Kanno A, Kato K, Tominaga T, Kawashima R,Nakasato N: Electro- and magneto-encephalographic spike source localization of small focal cortical dysplasia in the dorsal peri-rolandic region. Clin Neurophysiol 125: 2358-2363, 2014
  9. Kakisaka Y, Fujikawa M, Kaneko S, Nakasato N: Prolonged depersonalization/derealization-like symptom after migraine headache: a case report. Neurol Sci 35: 1483-1484, 2014
  10. Jin K, Nakasato N: Long-cherished dreams for epileptologists and clinical neurophysiologists: Automatic seizure detection in long-term scalp EEG. Clin Neurophysiol 125:1289-1290, 2014
  11. Kakisaka Y, Jin K, Kato K, Iwasaki M, Nakasato N: Temporal intermittent rhythmic delta activity and abdominal migraine. Neurol Sci 35: 627-628, 2014
  12. Shiraishi H, Haginoya K, Nakagawa E, Saitoh S, Kaneko Y, Nakasato N, Chan D, Otsubo H: Magnetoencephalography localizing spike sources of atypical benign partial epilepsy. Brain Dev 36:21-27, 2014
  13. Haginoya K, Uematsu M, Munakata M, Kakisaka Y, Kikuchi A, Nakayama T, Hino-Fukuyo N, Tsuburaya R, Kitamura T, Sato-Shirai I, Abe Y, Matsumoto Y, Wakusawa K, Kobayashi T, Ishitobi M, Togashi N, Iwasaki M, Nakasato N, Iinuma K: The usefulness of subtraction ictal SPECT and ictal near-infrared spectroscopic topography in patients with West syndrome. Brain Dev 35: 887-893, 2013
  14. Kawase T, Kanno A, Takata Y, Nakasato N, Kawashima R, Kobayashi T: Positive auditory cortical responses in patients with absent brainstem response. Clin Neurophysiol. 125: 148-153, 2014
  15. Kumabe T, Sato K, Iwasaki M, Shibahara I, Kawaguchi T, Saito R, Kanamori M, Yamashita Y, Sonoda Y, Iizuka O, Suzuki K, Nagamatsu K, Seki S, Nakasato N, Tominaga T. Summary of 15 years experience of awake surgeries for neuroepithelial tumors in Tohoku university. Neurol Med Chir (Tokyo). 53: 455-466, 2013
  16. Okumura E, Iwasaki M, Sakuraba R, Itabashi I, Osawa SI, Jin K, Itabashi H, Kato K, Kanno A, Tominaga T, Nakasato N: Time-varying inter-hemispheric coherence during corpus callosotomy. Clin Neurophysiol 124: 2091-2100, 2013
  17. Osawa S, Iwasaki M, Hosaka R, Matsuzaka Y, Tomita H, Ishizuka T, Sugano E, Okumura E, Yawo H, Nakasato N, Tominaga T, Mushiake H: Optogenetically induced seizure and the longitudinal hippocampal network dynamics. PLoS One. 10;8(4):e60928, 2013
  18. Iwasaki, M, Uematsu M, Nakayama T, Hino-Fukuyo N, Sato Y, Kobayashi T, Haginoya K, Osawa S, Jin K, Nakasato N, Tominaga T: Parental satisfaction and seizure outcome after corpus callosotomy in patients with infantile or early childhood onset epilepsy. Seizure. 22:303-305, 2013
  19. Shibahara I, Osawa SI, Kon H, Morita T, Nakasato N, Tominaga T, Narita N: Increase in the number of patients with seizures following the Great East-Japan Earthquake. Epilepsia 54: e49-52, 2013
  20. Nakasato N: Does measurement of event-related gamma-augmentation replace electrical stimulation via intracranial electrodes? Clin Neurophysiol 124: 829-830, 2013
  21. Iwasaki M, Uematsu M, Sato Y, Nakayama T, Haginoya K, Osawa S, Itabashi H, Jin K, Nakasato N, Tominaga T: Complete remission of seizures after corpus callosotomy. J Neurosurg Pediatr 10: 7-13. 2012
  22. Tanji K, Iwasaki M, Nakasato N, Suzuki K: Face specific broadband electrocorticographic spectral power change in the rhinal cortex. Neurosci Lett 515: 66-70. 2012
  23. Park HM, Nakasato N, Tominaga T: Localization of abnormal discharges causing insular epilepsy by magnetoencephalography. Tohoku J Exp Med 226: 207-211, 2012
  24. Takata Y, Kawase T, Nakasato N, Kanno A, Kobayashi T: Auditory evoked magnetic fields in patients with absent brainstem responses due to auditory neuropathy with optic atrophy. Clin Neurophysiol 123: 985-992, 2012
  25. Kawase T, Maki A, Kanno A, Nakasato N, Sato M, Kobayashi T: Contralateral white noise attenuates 40-Hz auditory steady-state fields but not N100m in auditory evoked fields. Neuroimage 59: 1037-1042, 2012 (PMID: 21945467)
    Iwasaki M, Nakasato N, Kakisaka Y, Kanno A, Uematsu M, Haginoya K, Tominaga T: Lateralization of interictal spikes after corpus callosotomy. Clin Neurophysiol. 122: 2121-2127, 2011
  26. Takada S, Iwasaki M, Suzuki H, Nakasato N, Kumabe T, Tominaga T: Angiocentric glioma and surrounding cortical dysplasia manifesting as intractable frontal lobe epilepsy--case report. Neurol Med Chir (Tokyo). 51: 522-526, 2011
  27. Kakisaka Y, Iwasaki M, Haginoya K, Kanno A, Tsuchiya S, Nakasato N: Somatotopic distribution of peri-rolandic spikes may predict prognosis in pediatric-onset epilepsy with sensorimotor seizures. Clin Neurophysiol. 122: 869-873, 2011
  28. Nakasato N: Point-to-point projection from muscle afferent to area 4 cortex. Clin Neurophysiol 122: 438-439, 2011
  29. Uematsu M, Haginoya K, Togashi N, Hino-Fukuyo N, Nakayama T, Kikuchi A, Abe Y, Wakusawa K, Matsumoto Y, Kakisaka Y, Kobayashi T, Hirose M, Yokoyama H, Iinuma K, Iwasaki M, Nakasato N, Kaneta T, Akasaka M, Kamei A, Tsuchiya S: Unique discrepancy between cerebral blood flow and glucose metabolism in hemimegalencephaly. Epilepsy Res 92: 201-208, 2010

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