Neuroradiology(1995) 37:526-530
9 Springer-Verlag 1995

T.Morioka
A.Mizushima
T. Yamamoto
S. Tobimatsu
S. Matsumoto
K. Hasno
K.Fnjii
M. Fukni

Received: 5 April 1994
Accepted: 13 July 1994
T.Morioka ( ~ ) - K.Fujii. M.Fukui
Department of Neurosurgery,
Neurological Institute,
Facultyof Medicine,KyushuUniversity60,
3-1-1 Maidashi,Higashi-ku,Fukuoka 81282, Japan
A. Mizushima S.Matsumoto 9K.Hasuo
Department of Radiology,
Facultyof Medicine,KyushuUniversity,
Fukuoka, Japan
T. Yamamoto
Department of Otolaryngology,
Faculty of Medicine,KyushuUniversity,
Fukuoka, Japan
S.Tobimatsu
Department of ClinicalNeurophysiology,
Neurological Institute,
Facultyof Medicine,KyushuUniversity,
Fukuoka, Japan

Functional mapping of the sensorimotor
cortex: combined use of
magnetoencephalography, functional MRI,
and motor evoked potentials

Abstract Combined use of magnetoencephalography (MEG), functional magnetic resonance imaging
(f-MRI), and motor evoked potentials (MEPs) was carried out on one
patient in an attempt to localise
precisely a structural lesion to the
central sulcus. A small cyst in the
right frontoparietal region was
thought to be the cause of generalised seizures in an otherwise asymptomatic woman. First the primary
sensory cortex was identified with
magnetic source imaging (MSI) of
somatosensory evoked magnetic
fields using MEG and MRI. Second,
the motor area of the hand was
identified using f-MRI during handsqueezing. Then transcranial magnetic stimulation localised the hand
motor area on the scalp, which was
mapped onto the MRI. There was a
good agreement between MSI,

Introduction
Precise determination of the anatomical relationship
between a lesion and the sensorimotor cortex can be important in deciding the appropriate surgical strategy in
the peri-rolandic area. Recent advances in noninvasive
localisation by the combined use of the magnetoencephalography (MEG) and imaging provide complementary
information for identification of the somatosensory cortex in normal volunteers [1-6] and patients with peri-rolandic lesions [7-12]. The resulting montage of information, which can aptly be called magnetic source imaging
(MSI) [7, 8, 11-14], is intriguing because it combines
structure and sensory function within an image.

f-MRI and MEP as to the location of
the sensorimotor cortex and its relationship to the lesion. Multimodality mapping techniques may thus
prove useful in the precise localisation of cortical lesions, and in the
preoperative determination of the
best treatment for peri-rolandic lesions.

Key words Functional magnetic
resonance imaging- Magnetic
source imagingMagnetoencephalography. Motor
evoked potentials

Many investigators have devised methods to elucidate the function of the motor cortex, including electrical stimulation [15] and positron emission tomography
[16]. Current research extends MRI methods to provide
information about function, the motor cortex being
identified by motor tasks, in addition to concomitant
anatomical information (functional MRI: f-MRI) [1725]. Furthermore, transcranial magnetic stimulation has
been developed for noninvasive stimulation of the human motor cortex [26, 27]. This technique has been used
to explore the functional anatomy of the motor cortex
by measuring motor evoked potentials (MEPs) following stimulation at multiple scalp sites [28-34]. We describe a multimodality mapping technique of the sen-

527

s o r i m o t o r c o r t e x in a p a t i e n t w i t h a l e s i o n in t h e f r o n t o p a r i e t a l r e g i o n , to e s t a b l i s h t h e v a l i d i t y o f t h e s e t e c h n i q u e s w i t h r e g a r d to a p p r o p r i a t e t r e a t m e n t .

Case report
A 40-year-old, right-handed woman was admitted with a long history of epilepsy; she experienced her first seizure at the age of
14 years. On admission, she had no neurological deficit. MRI revealed a lesion with long T1 and T2 medially in the right frontoparietal region (Fig. 1).
Magnetoencephalography
The patient underwent a localisation procedure for the hand sensory area by MSI. Our sensory mapping technique has been described previously [30]. In brief, the left thumb and little fingers
were stimulated mechanically and somatosensory evoked magnetic fields (SEFs) were measured in a magnetically shielded room
with a 37-channel neuromagnetometer, and the location of current
dipoles of SEFs was mapped on the MRI. MSI indicated that these
were located posterior to a large sulcus, which we deduced was the
central sulcus (Fig. 2 a, b). The lesion was medial to the hand sensory area, in both the sensory and motor areas of the cortex.

Fig.la, b MRI shows a lesion with long T1 and T2 medially in the
right frontoparietal region, a Tl-weighted sagittal, b T2-weighted
axial images

capsule was placed, and subsequent MR images were then obtained. Coronal imaging clearly demonstrated the scalp points over
the hand motor area on both sides (Fig. 3 b), which was consistent
with the f-MRI (Fig. 3 a). The lesion was thus found to be within an
eloquent area involving both sensory and motor cortex; radical
excision of the cyst and surrounding epileptogenic area would have
resulted in severe neurological deficits. Since drug treatment provided adequate seizure control, surgery was not carried out.

Functional MRI
Imaging was performed on a standard clinical 1.5 T system. The
patient was instructed to open and close the hand in a sequential,
self-paced, and repetitive manner. Multislice axial Tl-weighted
images were acquired before axial and coronal T2*-weighted images through the lesion; parameters for the latter were TR 80 ms,
TE 60 ms, flip angle 40 ~ acquisition time for each slice 16 s; slice
thickness was 7 mm. All subsequent analyses, including the functional maps, used 256 x 128 pixel points in a 24 x 18 cm field of
view. The effect of motor activation was assessed using difference
images generated by subtracting each T2* image from a baseline
image.
Axial f-MRI showed a high-signal activated region, surmised to
be the hand motor area (Fig.2c). The activated region corresponded well to the precentral gyrus as determined by MEG
(Fig. 2 b, c).
Motor evoked potentials
Transcranial magnetic stimulation was delivered with a magnetoelectric stimulator through a figure 8-shaped coil positioned with
its handle pointing along the sagittal axis and the centre (the intersection of the loops) lying flat on the scalp so that it was in contact with the scalp and close to the target. Electromyographic responses were recorded from surface electrodes placed over the
abductor pollicis brevis (APB) and amplified using a bandpass of
50 Hz and 3 kHz; the responses were recorded for 50 ms. At 100 %
of stimulator output, stimuli were delivered to positions over the
hemisphere contralateral to the muscle being recorded. Successive
positions 1 cm apart were stimulated until the area where MEPs
were produced was surrounded by inactive positions. Facilitation
methods such as voluntary contraction were not used.
The largest APB response was obtained i cm anterior to C3, C4
of the international 10-20 system, where a mark with a vitamin D

Discussion
The somatosensory magnetic field generated by neuroelectric activity passes through the inhomogeneities of
t h e c e r e b r o s p i n a l fluid, c r a n i u m a n d s c a l p e s s e n t i a l l y
u n i m p e d e d , so t h a t M S I s h o u l d l o c a l i s e s o u r c e s o f n e u r a l a c t i v i t y accurately. T h e a s s u m e d s p a c i a l a c c u r a c y o f
M S I w i t h r e s p e c t to l a n d m a r k s o n t h e h e a d is w i t h i n
3 m m [35]. R e c e n t l y , s e v e r a l g r o u p s [5, 8-10, 12] h a v e
confirmed the findings of MSI by intraoperative cortical
r e c o r d i n g o f s o m a t o s e n s o r y e v o k e d p o t e n t i a l s , thus vali d a t i n g t h e t e c h n i q u e . M E G also h a s b e e n e m p l o y e d to
m a p t h e o r g a n i s a t i o n of t h e a u d i t o r y c o r t e x [35], b u t h a s
n o t b e e n a p p l i c a b l e to a s s e s s m e n t o f t h e m o t o r cortex.
M R I h a s r e c e n t l y b e e n u s e d to e x a m i n e h u m a n cortical f u n c t i o n n o n i n v a s i v e l y , w i t h o u t t h e n e e d for e x o g e n o u s c o n t r a s t a g e n t s [17, 21, 25]. T h e r a t i o n a l e is t h a t
d e o x y h a e m o g l o b i n acts as a n e n d o g e n o u s p a r a m a g n e t i c
c o n t r a s t a g e n t [23, 26], c h a n g e s in its l o c a l c o n c e n t r a t i o n
l e a d i n g to a l t e r a t i o n s in t h e T 2 * - w e i g h t e d M R signal
[22, 24, 37]. N e u r a l a c t i v a t i o n w i t h i n t h e c e r e b r a l c o r t e x
l e a d s to a l a r g e i n c r e a s e in b l o o d f l o w w i t h o u t a n inc r e a s e o f s i m i l a r m a g n i t u d e in o x y g e n e x t r a c t i o n [38,
39], w h i c h in t u r n c a u s e s a d e c r e a s e in t h e c a p i l l a r y a n d
venous deoxyhaemoglobin concentration, producing an
i n c r e a s e in t h e T 2 * - w e i g h t e d M R signal ( b l o o d oxyg e n a t i o n l e v e l - d e p e n d e n t c o n t r a s t ) . T h e t e c h n i q u e has
b e e n a p p l i e d t o f u n c t i o n a l i m a g i n g of t h e h u m a n m o t o r
a n d visual c o r t e x at a h i g h m a g n e t i c field of 4 T [20, 25]

528

Fig.2a-c Magnetic source imaging indicating the current dipole (filled circle) in the postcentral thumb (a) and little finger areas (b) following mechanical somatosensory stimulation. The mass lesion lies medial to them. c Axial f-MRI,
slice corresponding to b, indicating the activated area as high
signal (arrows) during a motor
task. The activated region corresponds well to the precentral
gyrus as determined by magnetoencephalography

Fig.3 a Coronal f-MRI showing bilateral activated areas (arrows)
during a hand grip task. b Corresponding coronal Tl-weighted
image; the scalp, where the largest motor evoked potentials from
the hand were obtained, was marked with a vitamine D capsule
(arrows). The hand motor areas are consistent with the findings of
f-MRI

and using the high-speed echo-planar technique [7, 17,
19, 21]. In the present study, imaging was performed at a
clinical field strength of 1.5 T. The large signal changes
observed on f-MRI using standard clinical imagers operating at 1.5-2 T have been ascribed to direct inflow
effects of the venules; this does not exclude the use of
gradient-echo techniques for measurement of susceptibility changes, but indicates that inflow effects have to
be carefully accounted for.
There are still limitations to clinical f-MRI. Co-operation of the patient is essential to obtain a properly activated and balanced image; if the patient has a motor
deficit, the motor task will be impossible. Only a limited

number of scans may be performed in an individual
case. Although further technical development may be
necessary, our findings clearly demonstrate the promise
of using MRI in functional mapping.
Until recently, stimulation of the human cerebral cortex was confined to the operating room [40, 41]. With the
advent of transcranial magnetic stimulation, it has been
possible to investigate the human motor cortex safely
and painlessly [27]. It provides a noninvasive method of
topographical mapping of the human motor cortex [26].
Since a figure 8-shaped coil can deliver more focal magnetic stimulus than a routine coil with a 5-mm resolution
[32], it has been used to demonstrate the organisation of
the human corticomotor representation in normal subjects [28-31, 33, 34]. In our patient, we mapped the hand
motor area clearly on the MRI by MEPs. I in good
agreement with f-MRI. However, MEPs also cannot be
recorded in patients with weakness.
We found a good agreement between MEG, f-MRI
and MEP as to the location of the sensorimotor cortex
and its relationship to the lesion. Although there are still
some disadvantages of each method in practical use,
combined use of these mapping techniques appears to
overcome these difficulties. Multimodality mapping
techniques may thus be useful in the more precise localisation of cortical lesions and helpful in determining
the best form of treatment of peri-rolandic lesions.
Acknowledgements We thank Koichi Nitta and Yuko Somehara,
Bio-Medical Division, Sumitomo Metal Ind., LTD, and Yasuhiko
Nakamura, Radiology Centre of Kyushu University, for their
technical assistance. We also thank Dr. A.N. Kalehua, Max Planck
Institute for Psychiatry, Munich, for reviewing our manuscript.

References
1. Brenner D, Lipton J, Kaufman L, Williamson SJ (1978) Somatically evoked
magnetic fields of the human brain.
Science 199:81-83

2. Okada YC, Tannenbaum R, Williamson
SJ, Kaufman L (1984) Somatotopic organization of the human somatosensory
cortex revealed by neuromagnetic
measurements. Exp Brain Res 56: 197205

3. Orrison WW, Davis LE, Sullivan GW,
Mettler FA Jr, Flynn ER (1990) Anatomical localization of cerebral cortical
function by magnetoencephalography
combined with MR imaging and CT.
AJNR 11:713-716

529

4. Suk J, Ribary U, Cappell J, Yamamoto
T, Llinfis R (1991) Anatomical localization revealed by MEG recording of the
human somatosensory system. Electroencephalogr Clin Neurophysio178: 185196
5. Sutherling WW, Crandal PH, Darcey
TM, Becker DE Levesque MF, Barth
DS (1988) The magnetic and electrical
fields agree with intracranial localizations of somatosensory cortex. Neurology 38:1705-1714
6. Wood CC, Cohen D, Cuffin BN, Yarita
M, Allison T (1985) Electrical sources
in the human somatosensory cortex:
identification by combined magnetic
and electrical potential recording. Science 227:1051-1053
7. Benzel EC, Lewine JD, Bucholz RD,
Orrison WW Jr (1993) Magnetic source
imaging: a review of the Magnes system
of biomagnetic technologies incorporated. Neurosurgery 33:252-259
8. Gallen CC, Sobel DF, Waltz T, Aung M,
Copeland B, Schwartz B J, Hirschkoff
EC, Bloom FE (1993) Noninvasive presurgical neuromaguetic mapping of somatosensory cortex. Neurosurgery 33:
260-268
9. Kamada K, Takeuchi F, Kuriki S, Oshiro
O, Houkin K, Abe H (1993) Functional
neurosurgical simulation with brain
surface magnetic resonance images and
magnetoencephalography. Neurosurgery 33:269-273
10. Morioka T, Yamamoto T, Katsuta T,
Fujii K, Fukui M (1994) Presurgical 3dimensional magnetic source imaging
of the somatosensory cortex in a patient
with a peri-Rolandic lesion. Neurosurgery 34:930-934
11. Orrison WW Jr, Rose DF, Hart BL,
Maclin EL, Sanders JA, Willis BK,
Marchand ER Wood CC, Davis LE
(1992) Noninvasive preoperative cortical localization by magnetic source imaging. AJNR 13:1124-1128
12. Sobel DF, Gallen CC, Schwartz B J,
Waltz TA, Copeland B, Yamada S,
Hirschkoff EC, Bloom FE (1993)
Locating the central sulcus: comparison
of MR anatomic and magnetoencephalographic functional methods. AJNR
14:915-925
13. Williamson SJ, Kaufman L (1981) Biomagnetism. J Magnetism Magn Mater
22:129-202
14. Yamada S, Gallen CC (1993) Biomagnetic technologies: magnetic source imaging (MSI). Magnes Biomagnetometer. Neurosurgery 33:166-168

15. Cohen LG, Hallett M (1988) Methodology for noninvasive mapping of human motor cortex with electrical stimulation. Electroencephalogr Clin Neurophysiol 69:403-411
16. Roland PE, Meyer E, Shibasaki T,
Yamamoto YL, Thompson CJ (1982)
Regional cerebral blood flow changes
in cortex and basal ganglia during voluntary movements in normal volunteers. J Neurophysio148:467-480
17. Bandettini PA, Wong EC, Hinks PS,
Tikofsky RS, Hyde JS (1992) Time
course EPI of human brain function
during task activation. Magn Reson
Med 25:390-397
18. Belliveau JW, Kennedy DN, McKinstry
RC, Buchbinder BR, Weisskoff RM,
Cohen MS, Vevea JM, Brady TJ, Rosen
BR (1991) Functional mapping of the
human visual cortex by magnetic resonance imaging. Science 254:716-719
19. Belliveau JW, Kwong KK, Kennedy
DN, Baker JR, Stern CE, Benson R,
Chesler DA, Weisskoff RM, Cohen MS,
Tootell RBH, Fox PT, Brady TJ, Rosen
BR (1992) Magnetic resonance imaging
mapping of brain function. Human visual cortex. Invest Radio127:$59-$65
20. Kim S-G, Ashe J, Georgopoulos AR
Merkle H, Ellermann JM, Menon RS,
Ogawa S, Ugurbil K (1993) Functional
imaging of human motor cortex at high
magnetic field. J Neurophysiol 69: 297302
21. Kwong KK, Belliveau JW, Chesler DA,
Goldberg IE, Weisskoff RM, Poncelet
BR Kennedy DN, Hoppel BE, Cohen
MS, Turner R, Cheng H-M, Brady TJ,
Rosen BR (1992) Dynamic magnetic
resonance imaging of human brain activity during primary sensory stimulation. Proc Natl Acad Sci USA 89:
5675-5679
22. Ogawa S, Lee T-M (1990) Magnetic
resonance imaging of blood vessels at
high fields: in vivo and vitro measurements and image simulation. Magn Reson Med 16:9-18
23. Ogawa S, Lee T-M, Kay AR, Tank DW
(1990) Brain magnetic resonance imaging with contrast dependent blood oxygenation. Proc Natl Acad Sci USA 87:
9868-9872
24. Ogawa S, Lee T-M, Nayak AS, Glynn P
(1990) Oxygenation-sensitive contrast
in magnetic resonance image of rodent
brain at high magnetic fields. Magn Reson Med 14:68-78

25. Ogawa S, Tank DW, Menon R, Ellermann JM, Kim S-G, Merkle H, Ugurbil
K (1992) Intrinsic signal changes accompanying sensory stimulation: functional brain mapping with magnetic
resonance imaging. Proc Natl Acad Sci
USA 89:5951-5955
26. Amassian VE, Cracco RQ, Maccabee
PJ (1989) Focal stimulation of human
cerebral cortex with the magnetic coil: a
comparison with electrical stimulation.
Electroencephalogr Clin Neurophysiol
74:401-416
27. Barker AT, Jalinous R, Freeston IL
(1985) Non-invasive magnetic stimulation of the human motor cortex. Lancet
I: 1106-1107
28. Brasil-Neto JR McShane LM, Fuhr R
Hallett M, Cohen LG (1992) Topographic mapping of the human motor
cortex with magnetic stimulation: factors affecting accuracy and reproducibility. Electroencephalogr Clin Neurophysio185:9-16
29. Cohen LG, Roth B J, Wassermann EM,
Topka H, Fuhr P, Schultz J, Hallett M
(1991) Magnetic stimulation of the human cerebral cortex, an indicator of reorganization in motor pathways in certain pathological conditions. J Clin
Neurophysiol 8:56-65
30. Meyer B-U, Britton TC, Kloten H,
Steinmetz H, Benecke R (1991) Coil
placement in magnetic brain stimulation related to skull and brain anatomy.
Electroencephalogr Clin Neurophysiol
81:38-46
31. Mills KR, Boniface SJ, Schubert M
(1992) Magnetic brain stimulation with
a double coil: the importance of coil
orientation. Electroencephalogr Clin
Neurophysiol 85:17-21
32. Ueno S, Matsuda T, Fujiki M (1990)
Functional mapping of the human motor cortex obtained by focal and vectorial magnetic stimulation of the brain.
IEEE Trans Magn 26:1539-1544
33. Wassermann EM, McShane LM, Hallett M, Cohen LG (1992) Noninvasive
mapping of muscle representations in
human motor cortex. Electroencephalogr Clin Neurophysiol 85:1-8
34. Wilson SA, Thickbroom GW, Mastaglia
FL (1993) Transcranial magnetic stimulation mapping of the motor cortex in
normal subjects. The representation of
two intrinsic hand muscles. J Neurosci
118:134-144
35. Yamamoto T, Williamson SJ, Kaufman
L, Nicholson C, Llinfis R (1988) Magnetic localization of neural activity in
the human brain. Proc Natl Acad Sci
USA 85:8732-8736

530

36. Turner R, Le Bihan D, Moonen CWW,
Despres D, Frank J (1991) Echo-planar
time course M R I of cat brain oxygenation changes. Magn Reson Med 22:
159-166
37. Thulborn KR, Waterton JC, Matthews
PM, Radda GK (1982) Dependence of
the transverse relaxation time of water
protons in whole blood at high field.
Biochim Biophys Acta 714:265-270

French, R.: William Harvey's Natural Philosophy. Cambridge University Press.
(ISBN: 0-521-45535-9), Hardcover s 40.00.
This book, a study of a major change in
natural philosophy written by a professional historian for his peers, is not for the
casual historian or philosopher of science.
Dr French, a master of his subject and his
sources, addresses in a closely reasoned and
richly annotatednarrative the origins of
Harvey's natural philosophy, how it determined his approach to a problem, the
structure of his results and their expression
and led him to p0st;llate, following his
studies of the action of the heart, that the
blood must circulate. It also largely determined the way in which he marshalled his
evidence and presented his case in De rnotu
cordis. The author then goes on to consider,
in perhaps the most important section, how
individuals and their institutions with different philosophies both home and abroad
responded to Harvey's discovery and the
mechanisms that fostered or inhibited the
development of a consensus. For without
some form of consensus the concept of a
c~rculation would have remained an unorthodox view and natural philosophy and
medicine as a whole would have remained

38. Fox PT, Raichle ME (1986) Focal physiological uncoupling of cerebral blood
flow and oxidative metabolism during
somatosensory stimulation in human
subjects. Proc Natl Acad Sci U S A 83:
1140-1144
39. Fox PT, Raichle ME, Mintun MA,
Dence C (1988) Nonoxidative glucose
consumption during focal physiologic
neural activity. Science 241:462-464

40. Penfield W, Boldrey E (1937) Somatic
motor and sensory representation in the
cerebral cortex of man as studied by
electrical stimulation. Brain 60:389-443
41. Uematsu S, Lesser R, Fisher RS, Gordon B, Hara K, Krauss GL, Vining ER
Webber RW (1992) Motor and sensory
cortex in humans: topography studies
with chronic subdural stimulation.
Neurosurgery 31:59-72

unchanged. A m o n g the factors determining that response were the use of the formal
structures of argument and expression familiar to educated men and the influences
brought to bear on individuals through
their membership of medical, collegiate or
religious group. The author reminds us that
for most of Harvey's contemporaries the
main question was whether they could or
needed to reconcile his doctrines with more
important matters occupying their minds:
personal salvation; the correct interpretation of God's will; the coming millenium
and so forth. It is with hindsight that Harvey's discovery is seen as fundamental to a
later development of "biomedical science".
He goes on to consider at some length
Descartes's adoption, in modified form, of
Harvey's doctrines and the radical differences in their natural philosophies, the impact this had on their understanding from
the 1630s onwards and how it influenced
their acceptance or rejection.
There is much of interest to be learned
from Dr French's observations on the motives that led individuals (and institutions)
to reject Harvey's doctrines, ranging as
they did from the early and inplacab!e opposition of Primrose to the eminent anatomist Riolan, who as Dean of the Medical
Faculty of Paris had, as Harvey observed, a
duty to see that Galenic medicine was kept
in good repair. A major stumbling block to

the acceptance of Harvey's account of a total circulation was that it seemed to make
nonsense of bloodletting as a therapeutic
manoeuvre, based as it was on a Gelenic
concept of anatomy. Riolan, compelled by
a growing consensus to accept some form
of circulation, attempted to reconcile this
with what he previously believed and to
turn compromise to his advantage by making claims for his New Circulation. In his
reply, Harvey, now over 70 and used to
seeing his doctrine mutilated or dismembered as often as accepted, made one last
attempt to promote it. He pretended distain for his critics but his language was
bitter. The author concludes the last section
of the book, dealing with the development
of an experimental philosophy, with a
memorable summary: "the important event
in the Harvey business was not that the
light of Harvey's truth could no longer be
resisted, but that it came to be thought that
truth, or the best possible approximation to
it, could be discerned by experiment". This
was his true legacy.
A short review cannot do full justice to
a book described by its publishers as the
most extensive discussion of Harvey to
have been published for over 25 years.
Those who take the trouble to read it will
be richly rewarded.
T. D. Hawkins (Cambridge)