Department of Cognitive Neuroscience

Professor Morihiro Sugishita, Ph.D.

Associate Sotaro Sekimoto, Ph.D.


     The Department of Cognitive Neuroscience is one of the three departments composing the Speech and Cognitive Science Section. Since the establishment of this department in 1991, we have been working in the field of brain and cognition, especially language.

Research Activities

Current researches include:

1. Functional magnetic resonance imaging (fMRI) during writing.

     Recently, functional magnetic imaging(fMRI) techniques, sensitive to hemodynamic changes, have been shown to be quite useful for mapping of regional brain activation due to cognitive process. In this study fMRI was employed to determine which parts of the brain are activated during the performance of using Japanese phonograms or ideograms.
     There are two methods by which one can write: one is based on knowledge of how to convert speech sound (phoneme) to the corresponding letters (graphemes); the other is based on memory of specific letter-sequences (lexical). An ongoing study focussed on the former method. In English, phoneme-to-grapheme conversion is complex since most of phonemes are represented with two or more graphemes. For example, the phoneme /f/ is represented by the graphemes f, ph and gh. In Japanese, on the other hand, this conversion process is particularly simple and easy , since one phoneme is represented by only one grapheme (kana). In other word, phoneme-to-grapheme conversion in Japanese is one-to-one. The simplicity of phoneme-to-grapheme conversion in Japanese may explain the relative rarity of developmental dyslexia-dysgraphia in Japanese children. This study aimed to clarify using functional MRI the loci of brain activation related to writing by one-to-one phoneme-to-grapheme conversion. It also may enlighten the brain mechanism of writing in which occurrence of developmental dyslexia-dysgraphia is rare.

2. fMRI during recognition of newly learned face

     Face recognition is critical to the appreciation of our social and physical relations. Functional magnetic resonance imaging (fMRI) was used to identify brain regions involved in the recognition of newly learned faces. Our findings demonstrated that the bilateral fusiform gyrus is involved not only in face perception but in a certain aspect of face recognition memory and that this aspect is related to the actual recognition of previously viewed faces rather than the processing of novel ones, which results are consistent with previous lesion work. The right parietal and frontal regions, in contrast, are differentially more associated with the processes related to the detection of novel faces or retrieval effort.

3. A functional MRI study on speech dominance in a split-brain patient

     A large number of observations since the mid-nineteenth century have shown that damage to the left but not right hemisphere destroys language function. These observations lead to the formation of the "classic" view of a dominant language left hemisphere and a subordinate non-language right hemisphere. It thus came as a considerable surprise in the early 1960's when tests on commissurotomy or split-brain patients suggested the presence of a considerable capacity for language in the right hemisphere (Sperry 1981).
     Some investigators have argued, however, that the commissurotomy evidence may be misleading because the language of split-brain patients is atypical and is presented in both hemispheres even pre-operatively (Selnes 1976, Whitaker & Ojemann 1977). The present study aimed to clarify the problem using functional magnetic resonance imaging (fMRI) to examine pre-operatively an intractable epileptic who was scheduled to undergo section of the corpus callosum to reduce his epilepsy, and showed considerable reading comprehension 8 months post-operatively and so-called right hemisphere speech two years post-operatively.

4. Magnetoencephalographic studies of language

     Magnetoencephalography (MEG) is one of the recent noninvasive techniques for investigating human neuronal activities. MEG measures magnetic fields outside the skull, which is produced by electric current flow in the neural activities. MEG is especially good at tracing for sources in the cerebral cortex with millisecond range temporal resolution. The University of Tokyo Hospital has introduced a bland-new whole-head MEG system, VectorviewTM systems (Neuromag, LTD., Helsinki, Finland) in March 2000. With the systems, our laboratory is devoted to investigate such higher brain functions as image or language processing. As language studies, we have lately examined the reading process of Japanese phonograms. An ongoing study is concerning visual processing of printed words.

5. A magnetoencephalographic study of motor imagery

     Motor imagery is commonly used by sportsmen to improve their performance, since it aids motor skill acquisition. One of our recent MEG studies is regarding motor imagery. Subjects were instructed to imagine themselves hurdling self-centered space. In three of six subjects all 300 trials in the motor imagery condition revealed the precuneus dipole. When we divided the 300 trials into four overlapping blocks (one block = 150 trials), all six subjects showed precuneus activity. The latency of the precuneus dipole was about 220ms. The result suggests that the precuneus activity during motor imagery involves retrieval of spatial information and/or setting up spatial attributes. Only in one subject but twice, the current dipole located in the supplementary motor area was observed 60 ms after activation of the precuneus, which subjects that the signal from the precuneus for motor imagery is transferred to the supplementary motor area .

6. Aphasia therapy.

     The most important point in studying the effect of a treatment for aphasia is to verify that the observed improvement of performance is not due to spontaneous recovery but to the specific effect of the treatment. Thus, special experimental designs are necessary to confirm that the improvement of a patient's performance after treatment is significantly more than the spontaneous recovery. The present study employed a kind of single-case design called "a material-control single-case study" (Sugishita et al. 1993. Neuropsychol. 31, 559). We are studying whether or not initial syllable cueing is effective to improve naming performance in aphasics. Initial sound cueing is a technique in which the therapist gives the initial syllable of the word which the aphasic can not recall.

Teaching Activities

     There are 5 graduate students, one under graduate student and three visiting researchers. They have various back-ground including neurology, psychology, life science and so on.

Clinical Activities

     Assessment and therapy for aphasia, amnesia and dementia are conducted in collaboration with the Department of Neurology, Department of Neurosurgery and Department of Otorhinolaryngology.

References(1998-1999)

1) Nishiyama K, Sugishita M, Kurisaki H, Sakuta M: Reversible memory disturbance and intelligence impairment induced by long-term anticholinergic therapy, Internal Medicine 37: 514-518, 1998.
2) Kobayashi M, Takayama H, Mihara B, Sugishita M: Partial seizure with aphasic speech arrest caused by watching a popular animated TV program, Epilepsia 40: 652-654, 1999.
3) Tanaka S, Kanzaki R, Yoshibayashi M, Kamiya T, Sugishita M: Dichotic listening in Patients with situs inversus: brain asymmetry and situs asymmetry, Neuropsychologia 37: 869-874, 1999.