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Biomedical subjects

Y Hirayasu

Publications and source records attributed to Y Hirayasu.

29 records · Page 2Linked to original sources
PubMed1998

Abnormalities of auditory event-related potentials in schizophrenia prior to treatment.

BACKGROUND: P300 amplitude reduction is a consistent finding in schizophrenic patients, but it is unclear if this abnormality predates neuroleptic treatment or is present at onset of illness. METHODS: Auditory event-related potentials (ERPs), during a standard oddball paradigm, were recorded from 45 neuroleptic-naive schizophrenics, 56 drug-free, previously treated schizophrenics, and 73 healthy normal controls. Forty-seven of the schizophrenic subjects had their first episode within the past year. RESULTS: N200 amplitude did not differ among groups. P300 amplitude was significantly smaller in both neuroleptic-naive and previously treated schizophrenic groups compared to the control groups. There were no significant differences between the two schizophrenic groups in P300 amplitude. N200 and P300 latency were prolonged in previously treated schizophrenics compared to neuroleptic-naive schizophrenics and normal controls. CONCLUSIONS: The present study suggests that ERP abnormalities, especially P300 amplitude reduction, are already present prior to the administration of neuroleptic medication in the earliest stage of schizophrenia.

Adult↗
PubMed1998

Lower left temporal lobe MRI volumes in patients with first-episode schizophrenia compared with psychotic patients with first-episode affective disorder and normal subjects.

OBJECTIVE: Magnetic resonance imaging (MRI) studies of schizophrenic patients have revealed structural brain abnormalities, with low volumes of gray matter in the left posterior superior temporal gyrus and in medial temporal lobe structures. However, the specificity to schizophrenia and the roles of chronic morbidity and neuroleptic treatment in these abnormalities remain unclear. METHOD: Magnetic resonance (1.5-T) scans were obtained from 33 patients with first-episode psychosis and 18 age-matched normal comparison subjects, all right-handed. Sixteen of the patients were diagnosed with affective disorder and 17 with schizophrenia. RESULTS: Quantitative volumetric analysis showed that the patients with first-episode schizophrenia had significantly smaller gray matter volume in the left posterior superior temporal gyrus than did the patients with first-episode affective psychosis or the comparison subjects, with a significant left-less-than-right asymmetry. The schizophrenic patients also showed a smaller gray matter volume of the left posterior amygdala-hippocampal complex than the comparison subjects. Both the patients with schizophrenia and those with affective psychosis had significant left-less-than-right asymmetry of the posterior amygdala-hippocampal complex. CONCLUSIONS: These findings suggest that temporal lobe abnormalities are present at the first hospitalization for schizophrenia and that low volume of the left posterior superior temporal gyrus gray matter is specific to schizophrenia compared with affective disorder.

Adolescent↗
PubMed1998

MRI study of cavum septi pellucidi in schizophrenia, affective disorder, and schizotypal personality disorder.

OBJECTIVE: A cavum between the septi pellucidi may reflect neurodevelopmental anomalies in midline structures of the brain. The authors examined cavum septi pellucidi in subjects with schizophrenia, affective disorder, and schizotypal personality disorder and in normal subjects. METHOD: Thirty schizophrenic patients (15 chronic, 15 first-episode), 16 patients with affective disorder (first-episode), 21 patients with schizotypal personality disorder, and 46 normal subjects were evaluated with magnetic resonance imaging. Cavum septi pellucidi was assessed by counting the number of 1.5-mm slices containing cavum septi pellucidi. RESULTS: The presence or absence of cavum septi pellucidi did not differentiate among groups. However, the prevalence of abnormal cavum septi pellucidi (i.e., cavum septi pellucidi contained on four or more slices) was 30.4% for schizophrenic patients (36.4% for chronic, 25.0% for first-episode), 20.0% for patients with affective disorder, 18.8% for patients with schizotypal personality disorder, and 10.3% for normal subjects. When the authors used the Nopoulos et al. criteria for rating cavum septi pellucidi, which omitted borderline cases with cavum septi pellucidi on three slices, the prevalence of abnormal cavum septi pellucidi increased to 35.0% for schizophrenia (40.0% for chronic, 30.0% for first-episode), 25.0% for affective disorder, 27.3% for schizotypal personality disorder, and 13.0% for normal subjects. There was a statistically significant difference in ratings between schizophrenic and normal subjects. CONCLUSIONS: The results suggest that alterations in midline structures during the course of neurodevelopment may play a role in the pathogenesis of schizophrenia.

Adult↗
PubMed1998

Auditory mismatch negativity in schizophrenia: topographic evaluation with a high-density recording montage.

OBJECTIVE: The mismatch negativity, a negative component in the auditory event-related potential, is thought to index automatic processes involved in sensory or echoic memory. The authors' goal in this study was to examine the topography of auditory mismatch negativity in schizophrenia with a high-density, 64-channel recording montage. METHOD: Mismatch negativity topography was evaluated in 23 right-handed male patients with schizophrenia who were receiving medication and in 23 nonschizophrenic comparison subjects who were matched in age, handedness, and parental socioeconomic status. The Positive and Negative Syndrome Scale was used to measure psychiatric symptoms. RESULTS: Mismatch negativity amplitude was reduced in the patients with schizophrenia. They showed a greater left-less-than-right asymmetry than comparison subjects at homotopic electrode pairs near the parietotemporal junction. There were correlations between mismatch negativity amplitude and hallucinations at left frontal electrodes and between mismatch negativity amplitude and passive-apathetic social withdrawal at left and right frontal electrodes. CONCLUSIONS: Mismatch negativity was reduced in schizophrenia, especially in the left hemisphere. This finding is consistent with abnormalities of primary or adjacent auditory cortex involved in auditory sensory or echoic memory.

Acoustic Stimulation↗
PubMed1995

Transient P300 abnormality of event-related potentials following unilateral temporal lobectomy.

Event-related potentials (ERP) were recorded during auditory oddball tasks for a patient prior to and soon after left anterior temporal lobectomy. The N100 amplitude decreased bilaterally although the latency did not change after the lobectomy. The P300 amplitude decreased in the left hemisphere at 1 and 2 weeks after surgery, then recovered to the pre-operative level at 4 weeks. These findings suggest that the medial temporal structure participates in the generating system of P300.

Adult↗
PubMed1993

The effect of brainstem bisection prior to the amygdala kindling in rats.

This study examined the effect of selective midline sagittal section of the brainstem prior to kindling of the amygdala (AM) in rats. The brainstem section did not affect the AM kindling development at the primary site. However, some of the animals with brainstem section showed an absence of positive transfer effect (PTE) at the secondary site. These findings suggest that the brainstem has a probable role in PTE of rat AM kindling.

Amygdala↗
PubMed1992

Convulsive seizures in rats induced by N-methyl-D-aspartate injection into the massa intermedia.

The behavioral and electroencephalographic effects of N-methyl-D-aspartate (NMDA, 25 nmol/1 microliter) injection into the massa intermedia (MI) was examined in rats. The injection caused violent running/jumping and shrill vocalization without evidence of EEG seizure in the hippocampus (HP) and amygdala (AM). Animals with the injection site located in the reuniens nucleus subsequently developed generalized tonic and then clonic seizure, leading to fatal status epilepticus in some animals. Intermittent or continuous EEG discharge in the limbic system was found during clonic seizures. These findings suggest that the NMDA receptor in the reuniens nucleus in the MI participates in the generation and expression of convulsive seizure in rats.

Animals↗
PubMed1989

[Anticonvulsant effects of bifemelane hydrochloride on kindled seizures from the amygdala and hippocampus in rats].

The anticonvulsant affects of bifemelane hydrochloride, a novel therapeutic drug for cerebrovascular dementia, were investigated in the kindling model of epilepsy in rats. The results obtained were as follows. (i) Both the seizure stage and afterdischarge duration of kindled seizures from the amygdala and hippocampus were significantly suppressed following systemic injection of bifemelane hydrochloride (5-30 mg/kg) in a dose-dependent manner. (ii) The efficacy of anticonvulsant action on kindled seizures from the hippocampus was more potent than from the amygdala. (iii) The maximum anticonvulsant effects were observed between 1 and 4 h after injection, and this time course was very similar to that of the previously reported increasing effects of bifemelane hydrochloride on noradrenaline levels in the rat brain. Thus, it is suggested that these anticonvulsant effects in kindling may be mediated by central noradrenergic systems. These results indicate that bifemelane hydrochloride has a potent anticonvulsant action on kindled seizures and may be useful for dementia patients with epilepsy or other seizure disorders.

Amygdala↗
PubMedDate not supplied

Increase of methylguanidine and guanidinoacetic acid in the brain of amygdala-kindled rats.

Guanidino compounds are intrinsic chemoconvulsants. We investigated the regional and time-dependent changes of these compounds in the amygdala (AM) of kindled rats versus electroconvulsive shock (ECS) seizures using high-performance liquid chromatography (HPLC). Twenty-eight days after the last AM-kindled seizure, guanidinoacetic acid (GAA) and methylguanidine (MG) levels were significantly increased in the bilateral AM as compared with those of control rats, which had been implanted with electrodes but were not stimulated. Both compounds, however, tended to decrease in the bilateral AM after ECS seizure. In addition, we measured these compounds after induction of one afterdischarge (AD) in the AM. These compounds increased significantly 7 days after AD was induced in the ipsilateral AM. We suggest that the increase of these compounds is coincident with AD generation and specific to AM kindling and the kindled state.

Amygdala↗
PubMedDate not supplied

N-methyl-D-aspartate injection into the massa intermedia facilitates development of limbic kindling in rats.

The effect on limbic kindling of N-methyl-D-aspartate (NMDA) injection into the midline thalamus of rats was investigated. Repeated injection of 25 nmol/0.5 microliters NMDA (experimental group) into the massa intermedia (MI), particularly into the reuniens nucleus, caused tonic and/or clonic generalized convulsion associated with temporal limbic EEG seizure discharge. This did not occur after injection of phosphate-buffered saline (PBS, control group). When the animals were subjected to subsequent kindling at either the hippocampus (HP) or the amygdala (AM), only the experimental group showed a significant facilitation of kindling rate. The results suggest that an NMDA receptor in the reuniens nucleus participates in modulation of temporal limbic excitability and seizure development.

Amygdala↗