Sadato Laboratory - National Institute for Physiological Sciences

Profile of Norihiro Sadato

Education
Positions and Employment
Certification
Other Experience and Professional Memberships
Honors
List of 10 major publications
Description of the main scientific contribution

Education

1977-1979 Premedical Course, Faculty of Medicine, Kyoto University

1979-1983 Medical Course, Faculty of Medicine, Kyoto University (Degree: MD)

1990-1994 Postgraduate School (Internal Medicine), Kyoto University (Degree: PhD)

Positions and Employment

1983-1985 Resident, Medicine, Tenri Hospital, Nara, Japan

1985-1988 Resident, Department of Radiology, Tenri Hospital, Nara, Japan

1988-1990 Staff, Department of Radiology, Tenri Hospital, Nara, Japan

1988-1990 Clinical Fellow, Department of Neuroradiology, University of Maryland Medical System, Baltimore, Maryland, USA

1993-1995 Visiting Fellow, Human Motor Control Section, NINDS, NIH, Bethesda, USA

1995 Assistant Professor, Department of Radiology, Fukui Medical School, Fukui, Japan

1995-1998 Lecturer, Biomedical Imaging Research Center, Fukui Medical School

1998 Associate Professor, Biomedical Imaging Research Center, Fukui Medical School

1999-present Professor, Section of Cerebral Integration, Division of Cerebral Research, National Institute for Physiological Sciences, Okazaki, Japan

Certification

1983 National Medical Practitioner's, Japan

1991 Japanese Board of Radiology

Other Experience and Professional Memberships

1985-present Japanese Society of Radiology

1990-present Japanese Society of Nuclear Medicine

1990-present Society of Nuclear Medicine (USA)

1994-present American Academy of Neurology (Associate)

1994-present Society for Neuroscience (USA)

1995-present Japanese Society for Neuroscience

1997-present International Society of Cerebral Blood Flow and Metabolism

1998-present Japanese Society of Magnetic Resonance

Honors

1995 NIH 1995 Fellows Award for Research Excellence

1998 1998 The 36th Award of the Japanese Society of Nuclear Medicine

1999 1999 1998 Giovanni Di Chiro Award for Outstanding Scientific Research

List of 10 major publications

Sadato N, Zeffiro TA, Campbell G, Konishi J, Shibasaki H and Hallett M (1995) Regional cerebral blood flow changes in motor cortical areas after transient anesthesia of the forearm. Ann Neurol, 37: 74-81.
Okazawa H, Naito Y, Yonekura Y, Sadato N, Hirano S, Nishizawa S, Magata Y, Ishizu K, Tamaki N, Honjo I and Konishi J (1996) Cochlear implant efficiency in pre- and postlingual deafness A study withH215O and PET. Brain, 119: 1297-1306.
Sadato N, Pascual-Leone A, Grafman J, Ibanez V, Deiber M-P, Dold G and Hallett M (1996) Activation of the primary visual cortex by Braille reading in blind subjects. Nature, 380: 526-528.
Cohen LG, Celnik P, Pascual-Leone A, Corwell B, Faiz L, Dambrosia J, Honda M, Sadato N, Gerloff C, Catala MD and Hallett M (1997) Functional relevance of cross-modal plasticity in blind humans. Nature, 389: 180-183.
Yamada H, Sadato N, Konishi Y, Kimura K, Tanaka M, Yonekura Y and Ishii Y (1997) A rapid brain metabolic change in infants detected by fMRI. NeuroReport, 8: 3775-3778.
Sadato N, Pascual-Leone A, Grafman J, Deiber MP, Ibanez V and Hallett M (1998) Neural networks for Braille reading by the blind. Brain, 121: 1213-1229.
Morita T, Kochiyama T, Yamada H, Konishi Y, Yonekura Y, Matsumura M and Sadato N (2000) Difference in the metabolic response to photic stimulation of the lateral geniculate nucleus and the primary visual cortex of infants: a fMRI study. Neurosci Res, 38: 63-70.
Sadato N, Ibanez V, Deiber M-P and Hallett M (2000) Gender difference in premotor activity during active tactile discrimination. Neuroimage, 5: 532-540.
Yamada H, Sadato N, Konishi Y, Muramoto S, Kimura K, Tanaka M, Yonekura Y, Ishii Y and Itoh H (2000) A milestone for normal development of the infantile brain detected by functional MRI. Neurology, 55: 218-223.
Sadato N, Okada T, Honda M and Yonekura Y (2002) Critical period for cross-modal plasticity in blind humans: a functional MRI study. Neuroimage, 16: 389-400.

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Description of the main scientific contribution

1. Studies about cross-modal plasticity in the blind: Activation of the visual cortex of the blind during tactile discrimination.

Primary visual cortex receives visual input from the eyes, but is not known to receive input from other sensory modalities. To determine whether the visual cortex receives input from the somatosensory system, Sadato et al. (1996, 1998) used positron emission tomography (PET) to measure activation during tactile discrimination tasks in normal subjects and in Braille readers blinded in early life (before 14 y.o.). Blind subjects showed activation of primary and secondary visual cortical areas during tactile tasks, whereas normal controls showed deactivation. A simple tactile stimulus that did not require discrimination produced no activation of visual areas in either group. Thus in blind subjects, cortical areas normally reserved for vision may be activated by other sensory modalities.

The age dependency of this remarkable reorganization was investigated by fMRI (Sadato et al. 2002). Blind subjects, irrespective of the age at onset of blindness, exhibited higher activity in the visual association cortex than did sighted subjects. V1 was activated in blind subjects who lost their sight before 16 years of age, whereas it was suppressed in blind subjects who lost their sight after 16 years of age during a tactile discrimination task. This suggests that the first 16 years of life represent a critical period for a functional shift of V1 from processing visual stimuli to processing tactile stimuli.

To address the functional relevance of the visual cortices of the blind during tactile task, transcranial magnetic stimulation was utilized (Cohen et al. 1997, 1999) to disrupt the function of different cortical areas in people who were blind from an early age as they identified Braille or embossed Roman letters. Transient stimulation of the occipital (visual) cortex induced errors in both tasks and distorted the tactile perceptions of early blind, but not late blind subjects. In contrast, occipital stimulation had no effect on tactile performance in normal-sighted subjects. Taken together with the neuroimaging studies they conclude that blindness from an early age (before 15 y.o.) can cause the primary visual cortex to be recruited to a role in somatosensory processing.

2. Functional neuroimaging studies of babies

During development, the brain produces a vast excess of neurons, synapses, and dendritic spines as part of the maturational process. An age-related changes in synaptic density has been determined in the human primary visual cortex: rapid synapse production starts postnatally at the age of 2 months. To depict developmental changes of activity-related metabolism in human visual cortex, functional magnetic resonance imaging (fMRI) from the neonatal period was performed (Yamada, et al. 1997, 1999). A rapid metabolic changing pattern accompanying normal human brain maturation was revealed by fMRI with photic stimulation. Infants older than 8 weeks of age showed a stimulus-related signal decrease in the visual cortex, whereas younger neonates showed a signal increase. This inversion of response was not observed in the lateral geniculate nucleus which synaptogenesis is completed before delivery (Morita, et al. 2000). It is also independent of the white matter maturation (Yamada, et al. 1999). Hence inversion of the response suggests a change in oxygen consumption during neuronal activation, which is related to rapid synapse formation and accompanying increased metabolism. fMRI can detect dynamic metabolic changes during the brain maturation, and provides a new clue in the detection of abnormal brain development or central nervous system plasticity.