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Dive into the research topics where Kenichi Ueyama is active.

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Featured researches published by Kenichi Ueyama.


Psychiatry Research-neuroimaging | 1995

Proton magnetic resonance spectroscopy of the left medial temporal and frontal lobes in chronic schizophrenia: preliminary report

Hiroshi Fukuzako; Kouzou Takeuchia; Yoshiro Hokazono; Tsuyoshi Fukuzako; K. Yamada; Tomo Hashiguchi; Yoshihiko Obo; Kenichi Ueyama; Morikuni Takigawa; Toshiro Fujimoto

Proton magnetic resonance spectroscopy (MRS) was performed in 30 medicated schizophrenic patients and 30 normal subjects. Two groups, each containing 15 schizophrenic patients and 15 age-and sex-matched normal subjects, received MRS examinations for different volumes of interest, either the frontal lobe or the medial temporal lobe. Schizophrenic patients showed a decrease in the ratios of N-acetylaspartate (NAA)/choline-containing compounds (Cho) and NAA/creatine-phosphocreatine (Cr). The patients also showed an increase in the ratio of Cho/Cr in the left medial temporal lobe but not in the left frontal lobe. The age at onset of illness correlated positively with the ratios of NAA/Cho and NAA/Cr in the medial temporal lobe. No significant correlation was observed between the ratios of NAA/Cho, NAA/Cr, or Cho/Cr in the left medial temporal and frontal lobes and clinical symptomatology as assessed by the Scale for the Assessment of Negative Symptoms and the Positive and Negative Syndrome Scale.


Biological Psychiatry | 1996

Reduction in hippocampal formation volume is caused mainly by its shortening in chronic schizophrenia: Assessment by MRI

Hiroshi Fukuzako; Tsuyoshi Fukuzako; Tomo Hashiguchi; Yoshiro Hokazono; Kouzou Takeuchi; Kyuroku Hirakawa; Kenichi Ueyama; Morikuni Takigawa; Yoshiki Kajiya; Masayuki Nakajo; Toshiro Fujimoto

We performed contiguous, 1 mm thick, magnetic resonance imaging scans in 18 men with chronic schizophrenia and in 18 age-matched healthy subjects to test in living patients the findings of a previous postmortem study. The schizophrenic patients showed bilaterally shortening (left, -6%; right, -9%) and volume reduction (left, -9%; right, -11%) of the hippocampal formation (HF). Volumes of HF correlated positively with HF length in the schizophrenic patients. The reduction in bilateral HF volumes was small after controlling for HF lengths (left, -3%; right, -3%). In schizophrenic patients, significant negative correlations were found bilaterally between the length of HFs and the scores for attention, bizarre behavior, and positive formal thought disorder. The results suggest that the volume reduction seen in the HFs of schizophrenic patients was caused mainly by a shortening of the HF and that these clinical symptoms may be associated with shorter HF length.


Progress in Neuro-psychopharmacology & Biological Psychiatry | 1996

Phosphorus magnetic resonance spectroscopy in schizophrenia: Correlation between membrane phospholipid metabolism in the temporal lobe and positive symptoms

Hiroshi Fukuzako; Tsuyoshi Fukuzako; Kouzou Takeuchi; Yoshihiko Ohbo; Kenichi Ueyama; Morikuni Takigawa; Toshiro Fujimoto

1. To determine any correlations between phosphorus metabolites in the temporal lobes and clinical symptoms in schizophrenic patients, the authors performed 31phosphorus magnetic resonance spectroscopy in 31 medicated patients and age- and sex- matched normal subjects. 2. Schizophrenic patients demonstrated an increased level of phosphodiesters (PDE) in the temporal lobes bilaterally and a decreased level of beta-adenosine triphosphate (beta-ATP) in the left temporal lobe. 3. A significant positive correlation was observed between the level of PDE in the left temporal lobe and the score of positive symptoms on the Brief Psychiatric Rating Scale. 4. These results suggest that altered membrane phospholipid metabolism in the left temporal lobe is associated with neuroleptic-resistant positive symptoms in schizophrenic patients.


Psychiatry Research-neuroimaging | 1994

Correlation of third ventricular enlargement and EEG slow wave activity in schizophrenic patients

Kouzou Takeuchi; Morikuni Takigawa; Hiroshi Fukuzako; Yoshiro Hokazono; Kyuroku Hirakawa; Tsuyoshi Fukuzako; Kenichi Ueyama; Toshiro Fujimoto; Kei Matsumoto

Twenty-eight schizophrenic patients and 22 normal control subjects underwent magnetic resonance imaging (MRI) and topographic electroencephalography (EEG) in a study attempting to correlate morphological and electrophysiological findings. Schizophrenic patients had larger anterior horns of the lateral ventricles and third ventricles than normal control subjects. Schizophrenic patients showed more delta wave activity in the right parietooccipital region than normal control subjects. Alpha 2 wave activity was reduced in the entire region in schizophrenic patients. In schizophrenic patients, a significant positive correlation was seen between the area of the third ventricle and delta wave activity in the right occipital region. These results suggest that schizophrenic patients may have a dysfunction of diencephalic structures associated with morphological abnormality.


European Archives of Psychiatry and Clinical Neuroscience | 1994

31P magnetic resonance spectroscopy of the medial temporal lobe of schizophrenic patients with neuroleptic-resistant marked positive symptoms

Hiroshi Fukuzako; Kouzou Takeuchi; Kenichi Ueyama; Tsuyoshi Fukuzako; Yoshiro Hokazono; Kyuroku Hirakawa; K. Yamada; Tomo Hashiguchi; Morikuni Takigawa; Toshiro Fujimoto

Abstract31P magnetic resonance spectroscopy was performed in 16 medicated schizophrenic patients with neuroleptic-resistant marked positive symptoms and in 16 healthy volunteers matched for age and sex in order to determine what changes in phosphorus metabolites are detected in such patients as compared to the controls. The schizophrenic patients showed an increased level of phosphodiesters in the bilateral medial temporal lobes. They also showed a decrease in the level of β-ATP in the left medial temporal lobe. These findings suggest that schizophrenic patients with prominent positive symptoms refractory to neuroleptics may have a disturbance of bilateral membrane phospholipid and left-sided high-energy phosphate metabolism in the medial temporal lobe.


Psychiatry and Clinical Neurosciences | 1995

Shortening of the hippocampal formation in first‐episode schizophrenic patients

Hiroshi Fukuzako; Satoshi Kodama; Tsuyoshi Fukuzako; Koichiro Yamada; Yoshiro Hokazono; Kenichi Ueyama; Tomo Hashiguchi; Kaoru Takenouchi; Morikuni Takigawa; Kouzou Takeuchi; Surendra Manchanda

Abstract Shortening of hippocampal formation (HF) in chronic schizophrenic patients have been demonstrated in our previous study. The purpose of the present study is to test if shortening of the HF occurs in schizophrenic patients suffering their initial psychotic episode. We performed contiguous, 1 mm thick, magnetic resonance imaging scans in 20 first‐episode schizophrenic patients, 21 chronic schizophrenic patients, and 25 healthy subjects. Both groups of schizophrenic patients demonstrated significant shortening of the HF compared with normal controls (first‐episode schizophrenia, 5.3%; chronic schizophrenia, 8.0%). However, the HF length was not significantly different between the first‐episode and chronic schizophrenic patients. No significant correlation was seen between the HF length and the duration of illness in chronic schizophrenic patients. These results suggest that the HF shortening observed in schizophrenic patients may be genetic and/or developmental in origin.


Progress in Neuro-psychopharmacology & Biological Psychiatry | 1999

P300 event-related potentials in probable dissociative generalized amnesia

Hiroshi Fukuzako; Syuichi Fukuzaki; Tsuyoshi Fukuzako; Hongkui Jing; Kenichi Ueyama; Morikuni Takigawa

1. To investigate whether abnormalities in objective neurophysiologic measures are observable in patients with probable dissociative generalized amnesia, the P300 and N100 event-related potentials were evaluated in six such patients in both acute stage and after recovery from amnesia. Findings were compared with those in 12 age- and gender-matched healthy subjects. 2. While latencies did not differ from those of control subjects, P300 amplitudes in acute-stage recordings were lower than those in controls. Repeated recordings in the patients showed a significant increase in P300 amplitude after recovery from amnesia. 3. Amplitude and latency of N100 did not differ between the patient and control groups, nor changed significantly after retrieval of memory. 4. These findings suggest that some unknown biological and/or psychologic mechanisms that cause retrograde autobiographic amnesia may impair cognitive function as reflected in an objective neurophysiologic measure such as the P300.


Psychiatry and Clinical Neurosciences | 1990

THREE CASES OF CHRONIC SUBDURAL HEMATOMA WITH DEPRESSIVE STATE

Itsugi Nagatomo; Kenichi Ueyama; Hiroshi Fukuzako; Kei Matsumoto

Abstract: The authors described 3 cases of chronic subdural hematoma (CSDH) with a depressive state. There were no abnormal findings from general and neurological examinations. Computed tomographic (CT) brain scans revealed sickle‐shaped low density areas in the bilateral frontal lobes. Two of the 3 cases had not had episodes of head contusion, and it was not until the CT brain scanning that they were found to have CSDH. Evacuation of the hematomas was not considered suitable and the depressive state of these 2 cases was improved by antidepressants. The remaining case seemed to have become depressive because of failure in business. After the head contusion, his depressive state gradually became more severe. A neurosurgical operation was carried out to evacuate the hematoma. CSDH seemed to aggravate his depressive state. These 3 cases show that CSDH located in the bilateral frontal lobes may cause and/or influence affective disorder.


Canadian Journal of Physiology and Pharmacology | 1993

A dual approach to self-stimulation and locomotor trace affected by chronic methamphetamine treatment for an animal model of schizophrenia

Morikuni Takigawa; Hiroshi Maeda; Kenichi Ueyama; Hidefumi Tominaga; Kei Matsumoto


International Journal of Geriatric Psychiatry | 1994

CT study in senile dementia of Alzheimer type

Kenichi Ueyama; Hiroshi Fukuzako; Tsuyoshi Fukuzako; Yoshirou Hokazono; Kouzou Takeuchi; Tomo Hashiguchi; Morikuni Takigawa; Takao Yamanaka; Kei Matsumoto

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Toshiro Fujimoto

Tokyo Medical and Dental University

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