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Biomedical subjects

Eiji Kirino

Publications and source records attributed to Eiji Kirino.

7 recordsLinked to original sources
PubMed2006

P300 is attenuated during dissociative episodes.

The present study examined the pathophysiology of dissociative phenomena using the P300 component of event-related potentials, quantitative electroencephalography (QEEG), and morphology measures of computed tomography scan. Event-related potentials during an auditory oddball paradigm and QEEG in resting state were recorded. Patients exhibited attenuation of P300 amplitudes compared with controls during dissociative episodes, but exhibited recovery to control levels in remission. Patients had a larger Sylvian fissure-brain ratio than did controls. QEEG findings revealed no significant differences between the patients and controls or between episodes and remission in the patient group. Attenuation of the P300 can be interpreted as the result of a negative feedback loop from the medial temporal lobe to the cortex, which decreases the amount of information flow, allocation of attentional resources, and updating of working memory to avoid both excessive long-term memory system activity in medial temporal lobe and resurgence of affect-laden memories.

Acoustic Stimulation↗
PubMed2005

Schizophrenic patients are impaired in memory reinstatement underlying mismatch negativity system.

OBJECTIVE: We modified the paradigm used in the report of Cowan et al. [J Exp Psychol Learn Mem Cogn 19 (1993) 909] to investigate how the silent intervals influence the memory trace underlying mismatch negativity (MMN) generation in schizophrenic patients. METHODS: Experiment 1 was designed to explore how long an inter-train interval would be needed for the memory to become dormant. Experiment 2 was designed to elucidate how many standard stimuli would be needed to reinstate the memory. RESULTS: In Experiment 1, schizophrenic patients showed a significant reduction in MMN amplitude after the longer inter-train intervals compared to the shorter ones, although little difference was observed in controls. Specifically, the memory trace underlying the MMN system in the schizophrenic patients easily became dormant after the extended silent intervals. In Experiment 2, we could not conclude that schizophrenic patients needed more reminders than did controls in order to reinstate the memory once the memory trace became dormant. The patients might be little impaired with respect to forming the memory trace. CONCLUSIONS: In schizophrenic patients, the memory trace in MMN generation might easily become out of context after silent intervals. Patients could not effectively reinstate the memory that was put out of context by the extended silent interval. SIGNIFICANCE: This article provides some suggestions in terms of patients' difficulty encoding episodes and retrieving them within distinct contexts in preconscious processes.

Acoustic Stimulation↗
PubMed2005

Transdermal nicotine administration enhances automatic auditory processing reflected by mismatch negativity.

Mismatch negativity (MMN) is a component of event-related potentials (ERPs) with a wide-ranging applicability to the investigation of neuronal substrates of information processing in normal and psychopathological states. Nicotine has been shown to be implicated in the pathophysiology of psychiatric disorders as schizophrenia or Alzheimer's disease, and has also been proposed as a self-administered drug in schizophrenia. The goal of the present study is to elucidate the effect of nicotine on the auditory automatic processing reflected by MMN. Nicotine was administered transdermally under controlled dosage. Ten healthy volunteers attended the laboratory for one baseline session and two test sessions. The test sessions involved administration of a placebo patch and a nicotine skin patch, which were counter-balanced. The ERPs were recorded passively during an auditory oddball paradigm. Nicotine administration shortened the MMN latencies, and these effects were independent of the earlier ERP components, N100 and P200. In conclusion, nicotine enhances preattentive and automatic processing such as MMN system and these effects appear to be quite specific and independent of earlier cognitive stages than preattentive mismatch processing. The shortened MMN latency may be interpreted as a reduction of the amount of time required to complete a neuronal mismatch process through the ascending auditory pathway.

Acoustic Stimulation↗
PubMed2004

Irreversible subcortical dementia following high altitude illness.

In this report, we present the cases of two 63-year-old women who developed high altitude cerebral edema complicated by the occurrence of permanent neuropsychiatric sequelae. They shared a similar clinical course, in that both developed disturbance of consciousness shortly after their arrival at Cuzco, Peru (3500 m), and both developed persistent neuropsychiatric symptoms after resolution of the acute illness. Interestingly, in case 2 there was a 1-month lucid interval between remission of high altitude illness and occurrence of the irreversible neuropsychiatric sequelae. Brain computerized tomography in case 1 and brain magnetic resonance imaging in case 2 disclosed lesions in the globus pallidus bilaterally, suggesting that the neuropsychiatric symptoms in these patients were manifestations of subcortical dementia. The development of high altitude illness was considered to be attributable to mild restrictive lung impairment in case 1 and to a deficient ventilatory response to hypoxia in case 2. It must therefore be borne in mind that irreversible subcortical dementia may be associated with high altitude cerebral edema.

Acute Disease↗
PubMed2004

Correlation between P300 and EEG rhythm in schizophrenia.

We hypothesized that cognitive deficits reflected by P300 abnormality and distorted EEG rhythm in schizophrenia, which might share the subcortical generation system, could be closely associated with each other. Our goal is to assess the relationship between P300 and EEG rhythm generation in schizophrenics. Quantitative EEG (QEEG) in resting condition and P300 during auditory oddball paradigm were recorded with 25 unmedicated patients. Additionally, lateral ventricular-brain ratio (LV-BR), which partially reflects thalamic volume, was measured using CT scan. Brief Psychotic Rating Scale (BPRS) and Scale for Assessment of Negative Symptoms (SANS) were also rated. P300 amplitudes at Pz positively correlated with theta and slow alpha power before pharmacotherapy, however, the correlation tended to be confined to fast alpha after pharmacotherapy. BPRS and SANS showed no significant correlation with QEEG. High frequency bands such as fast alpha and beta showed trends to correlate negatively to LV-BR. The lack of correlation between P300 amplitudes and fast alpha power before pharmacotherapy, which was restored after pharmacotherapy, might indicate thalamocortical dysfunction in schizophrenia.

Adolescent↗
PubMedDate not supplied

Risperidone withdrawal-related respiratory dyskinesia: a case diagnosed by spirography and fibroscopy.

Risperidone is a frequently used member of a new class of atypical antipsychotics-the serotonin-dopamine antagonists (SDAs)-due to its comparatively high efficacy and low D2/5HT2 binding ratio, which results in a low incidence of extrapyramidal side effects including tardive dyskinesia (TD). The authors present an elderly patient with mixed dementia who developed TD at multiple sites, (including respiratory dyskinesia [RD], limb dyskinesia, and orofacial dyskinesia) following abrupt withdrawal of risperidone therapy. RD is not a rare condition, but is often misdiagnosed and is potentially lethal. Therefore, clinicians should pay close attention to possible onset of RD in patients with multiple risk factors for TD, even when SDA therapy is used. If RD is suspected, assessment should include spirography combined with fibroscopy for examination of irregularities in the rate, rhythm, and depth of respiration.

Aged↗