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ABSTRACT: Time domain analysis of electroencephalography (EEG) can identify subsecond periods of quasi-stable brain states. These so-called microstates assumingly correspond to basic units of cognition and emotion. On the other hand, Global Field Synchronization (GFS) is a frequency domain measure to estimate functional synchronization of brain processes on a global level for each EEG frequency band [Koenig, T., Lehmann, D., Saito, N., Kuginuki, T., Kinoshita, T., Koukkou, M., 2001. Decreased functional connectivity of EEG theta-frequency activity in first-episode, neuroleptic-naive patients with schizophrenia: preliminary results. Schizophr Res. 50, 55-60.]. Using these time and frequency domain analyzes, several previous studies reported shortened microstate duration in specific microstate classes and decreased GFS in theta band in drug naïve schizophrenia compared to controls. The purpose of this study was to investigate changes of these EEG parameters after drug treatment in drug naïve schizophrenia. EEG analysis was performed in 21 drug-naive patients and 21 healthy controls. 14 patients were reevaluated 2-8 weeks (mean 4.3) after the initiation of drug administration. The results extended findings of treatment effect on brain functions in schizophrenia, and imply that shortened duration of specific microstate classes seems a state marker especially in patients with later neuroleptic responsive, while lower theta GFS seems a state-related phenomenon and that higher gamma GFS is a trait like phenomenon.
Schizophrenia Research 01/2008; 97(1-3):163-72. · 4.75 Impact Factor
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ABSTRACT: EEG frequency-domain analyses have demonstrated that cognitive performance produces a reduction in alpha activity, i.e., alpha attenuation, such as event-related desynchronization (ERD), reflecting brain activation. To examine whether schizophrenic patients have abnormalities in frequency-domain, event-related alpha attenuation, as well as in time-domain EEG phenomena, such as event-related potential, we compared alpha power change and P300 elicited simultaneously in response to the presentation of target tones in an auditory oddball paradigm between patients with schizophrenia and normal control subjects. In both patients and controls, alpha power was smaller during the time window of 512 ms following targets than following non-targets, particularly at the parietal and the posterior temporal locations (Pz, T5, and T6). The size of alpha attenuation measured as percent reduction in alpha power produced by targets relative to non-targets was smaller in patients than in controls at the posterior temporal locations. The size of alpha attenuation showed no correlation with P300 amplitude or latency in either patients or controls. Furthermore, in patients, the size of alpha attenuation showed no correlation with symptom severity, while P300 amplitude was correlated negatively with the positive subscale score of the Positive and Negative Syndrome Scale. These findings suggest that the symptom-independent reduction in event-related alpha attenuation in schizophrenia may be useful as an electrophysiological index of the impairment of neural processes distinct from that indexed by symptom-dependent P300 abnormalities.
International Journal of Psychophysiology 09/2007; 65(2):95-102. · 2.14 Impact Factor
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ABSTRACT: Abnormalities of electroencephalographic (EEG) coherence in schizophrenia are thought to reflect functional disconnections between different brain regions associated with the onset of this disease. To clarify whether these abnormalities change in a symptom-dependent manner in individual patients, we analyzed the coherence of resting EEGs recorded at two time points with a 36.6-day interval during the course of treatment for 14 patients who had been hospitalized for acute exacerbation of schizophrenia. Symptom severity was quantitatively measured by means of the Brief Psychiatric Rating Scale (BPRS). Beta (13-20 Hz) coherence for the left frontal (F7)-temporal (T5) electrode pair was less than that for the corresponding right pair (F8-T6) at the initial test. At the second test, when symptoms had improved, the left frontal-temporal beta coherence had increased, resulting in disappearance of the laterality. This change in beta coherence for the left frontal-temporal pair correlated negatively with the change in the total BPRS score, particularly the positive symptom score. Similar correlations were found for eight patients who had been drug-free at the first examination. These results suggest that a functional disconnection between the frontal and the temporal lobe in the left hemisphere may be associated with the generation of acute psychotic symptoms in schizophrenia.
Psychiatry Research 02/2007; 149(1-3):41-7. · 2.52 Impact Factor
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ABSTRACT: To clarify whether interhemispheric electroencephalogram (EEG) coherence reflecting functional connectivity between the two cerebral hemispheres can change in a symptom-dependent manner in schizophrenia, we measured resting EEG and symptom severity twice at an average interval of 32.7 days during the course of treatment in 15 patients hospitalized for acute exacerbations of schizophrenia. Symptom severity was estimated quantitatively by means of the Brief Psychiatric Rating Scale (BPRS). Correlation analysis showed that increases in the beta-band coherence for frontal electrode pairs during the treatment were associated with improvement in the total score and the score on the positive subscale of BPRS. This result suggests that functional disconnection between the left and right frontal lobes may be related to the generation of psychotic symptoms and can normalize following antipsychotic treatment.
Clinical EEG and neuroscience: official journal of the EEG and Clinical Neuroscience Society (ENCS) 02/2006; 37(1):10-5. · 1.73 Impact Factor
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ABSTRACT: An attention-related, negative component can be detected between the N100 peak and 200 ms after stimulus by subtracting event-related potentials (ERPs) elicited to background tones when subjects ignore tones, from ERPs elicited to background tones when subjects attend to tones to detect target tones in an oddball paradigm. To clarify the cognitive significance of this component in schizophrenia, we examined the correlations of 24 patients between the amplitude and latency of the negative component and results obtained using neuropsychological measurement methods, including the Wisconsin Card Sorting Test, the Trail Making Test, the Verbal Fluency Test and some subtests from the Wechsler Memory Scale. The latency prolongation of the negative component correlated positively with the difference in performance time between parts A and B of the Trail Making Test, which estimates set shift, a frontal-lobe executive function, but not with any other neuropsychological measurements, while the amplitude showed no such correlation. These results suggest that the latency prolongation of the attention-related, negative component induced in an auditory oddball paradigm may serve as an index for frontal dysfunction in schizophrenia.
Neuropsychobiology 02/2005; 51(4):177-82. · 2.67 Impact Factor
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ABSTRACT: The main purpose of this study was to investigate the relationship between short-term clinical outcome and changes in electroencephalogram (EEG) power after drug treatment in patients with schizophrenia, and also to compare two different methods for quantitative EEG analysis. EEG power analysis was performed by both conventional fixed frequency band and adjusted frequency band based on individual alpha frequency (IAF) in 16 drug-naive patients before and after drug administration. In the theta bands determined by both conventional fixed band and IAF methods, the EEG power after treatment was larger than that before treatment. In addition, there was a correlation between EEG power and clinical drug response evaluated by changes in BPRS score. With regard to this correlation, IAF methods showed no apparent advantage over methods using conventional fixed frequency bands. Conventional quantitative EEG analysis can still serve as a useful tool for the assessment of short-term outcome of drug treatment.
Neuropsychobiology 02/2005; 51(4):183-90. · 2.67 Impact Factor
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ABSTRACT: A severe intractable delirium caused by the basal forebrain vascular lesion and its dramatic recovery after donepezil administration were reported. A 68-year-old man had suffered for a month from delirium of mixed type caused by the right basal forebrain vascular lesion after surgery for craniopharyngioma. Magnetic resonance imaging (MRI) showed hemorrhagic infarcts in the head of the right caudate nucleus and the right basal forebrain of the medial septal nucleus, diagonal band of Broca and nucleus basalis of Meynert. He had been treated with anti-psychotics, anti-depressants and hypnotics, which resulted in little improvement. Donepezil administration dramatically improved his intractable delirium at the 19th post-donepezil administration day, but this was followed by amnestic symptoms. Clinical correlates of delirium with the basal forebrain lesion and efficacy of donepezil support the hypocholinergic theory of delirium.
Progress in Neuro-Psychopharmacology and Biological Psychiatry 12/2004; 28(7):1189-94. · 3.25 Impact Factor
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European Psychiatry 10/2004; 19(6):380-1. · 2.77 Impact Factor
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ABSTRACT: It has been reported that in event-related potentials (ERPs) elicited by non-target tones in oddball paradigms, the superimposition of a negative component on the descending slope of N100 depends on subjects' attention to the task. We tested the possibility that this attention-related change is abnormal for patients with schizophrenia. ERPs induced by non-target, frequent tones were measured for 52 patients and 31 healthy controls under two oddball conditions: a passive condition where the subjects were told to disregard the tones, and an active condition where they were instructed to respond to infrequent tones. For both groups, a negative component was superimposed from the descending slope of N100 to the end of P150 (latency, 120-200 ms) for the active condition. The peak latency of this attention-related negative component was longer for the patients than for the controls, while the amplitude showed no group difference. In addition, the active P150 for the patients was more enlarged than that for the controls. Furthermore, the active P150 amplitude for the patients correlated positively with the score for the negative symptom factor of the Positive and Negative Syndrome Scale. These findings suggest that the enlargement of non-target P150 observed in conjunction with the latency prolongation of the attention-related negative component may be a biological marker for the severity of the negative symptoms in schizophrenia.
International Journal of Psychophysiology 03/2004; 51(3):189-200. · 2.14 Impact Factor
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ABSTRACT: The amplitude of the P300 component of the auditory event-related brain potential (ERP) is consistently reduced in schizophrenia. To determine whether this P300 abnormality can be used as a state marker to reflect the severity of symptoms, we examined both cross-sectionally and longitudinally the relationship between auditory P300 amplitude and symptom severity in patients with schizophrenia. For the cross-sectional study, ERP was elicited by an auditory oddball paradigm, and symptom severity was quantitatively measured by means of the Positive and Negative Syndrome Scale in 93 patients with schizophrenia or schizophreniform disorder (DSM-III-R). For the longitudinal study, ERP and psychopathology measured twice at an average interval of 238 days for 20 patients were retrospectively analyzed. The cross-sectional data showed that P300 amplitude correlated negatively with the positive but not with the negative syndrome scale score. The longitudinal data also showed a significant negative correlation between changes in P300 amplitude and in the positive syndrome scores of the first and second tests. In particular, P300 amplitude recorded at the left, but not right, posterior temporal region significantly correlated with the positive syndrome in both the cross-sectional and longitudinal studies. These findings support the hypotheses that auditory P300 amplitude recorded in the left hemisphere can be used as a state marker to reflect the severity of the positive symptoms and that the positive symptoms may be caused by a possible left-hemisphere deficit in schizophrenia.
Schizophrenia Research 03/2003; 59(2-3):147-57. · 4.75 Impact Factor
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ABSTRACT: This study assessed the effects of drugs which manipulate the cAMP system on afterdischarges (ADs) induced in the CA1 region of rat hippocampal slices. The adenylate cyclase activator forskolin (50 microM) and the phosphodiesterase inhibitor rolipram (0.1 and 1 microM) enhanced AD generation. These effects were reversed by the cAMP-dependent protein kinase inhibitors H-89 (5 microM) and Rp-cAMPS (100 microM). These findings suggest that AD generation can be modulated through cAMP generation and the subsequent activation of the cAMP-dependent protein kinase.
Brain Research 10/2002; 949(1-2):157-61. · 2.73 Impact Factor
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Tetsumori Yamashima,
Manami Yoshida,
Kazuhiko Kumahashi,
Mie Matsui,
Yoshifumi Koshino, Masato Higashima,
Tatsuya Nagasawa,
Akira Ueki,
Mieko Ohtsuka,
Shozo Aoki, [......],
Yoshio Minabe,
Yoshio Nanba,
Mayumi Nanba,
Jun-ichi Kira,
Yasumasa Ohyagi,
Joh Haraoka,
Jiro Akimoto,
Nobuyoshi Miura,
Shingo Kimura,
Masaaki Matsushita
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ABSTRACT: In Japan, neuropsychological assessment of dementing illnesses has been done mainly using Mini-Mental State Examination (MMSE) and a revised version of Hasegawa Dementia Scale (HDS-R). However, because of a lack of appropriately designed test domains, early detection of senile dementia and/or cognitive impairment is hardly possible, even if using these batteries. This paper is to introduce a Japanese Version of RBANS (Repeatable Battery for the Assessment of Neuropsychological Status) which was originally developed by Randolph and revised by us. The entire battery of Japanese Version RBANS took less than 30 minutes to administer, and yielded scaled scores for five cognitive domains such as immediate memory, visuospatial/constructional ability, language, attention, and delayed memory. On RBANS, abnormal cognitive decline in the older adult was much easily detected, being compared to MMSE and HDS-R: 52 normal volunteer subjects ranging from 24 to 80 years old showed a significant (p < 0.05 on t test) impairment of delayed and immediate memories due to ageing. The aged (60-79) subjects with average scores of MMSE and HDS-R being over 25, significantly showed impairment of both immediate memory (list and story learnings) and delayed memory (list, story and figure recalls). The present data suggest that the Japanese Version RBANS is useful for both detecting and characterizing early dementia, and should be widely utilized for a neuropsychological screening battery in the clinical practice throughout Japan.
Nō to shinkei = Brain and nerve 06/2002; 54(6):463-71.
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ABSTRACT: We have recently reported that ictal-like afterdischarges (ADs) analogous to those in in vivo kindling models are induced by high-frequency stimulation (100 Hz, 1s) to the stratum radiatum of the CA1 region of rat hippocampal slices. To test whether this model can also serve as an in vitro seizure model for temporal lobe epilepsy, we examined the effects of antiepileptic drugs on this model and compared them with their effects on seizures in patients with temporal lobe epilepsy. ADs were progressively enhanced following repetitive high-frequency stimulations to slices treated with 4-aminopyridine, a proconvulsive A-type potassium channel blocker. Bath application of phenytoin (1-100 microM) and carbamazepine (1-100 microM) suppressed AD generation in a concentration-dependent manner. At a clinically relevant concentration of 10 microM, phenytoin reduced the number of spikes in an AD to 50.6% and carbamazepine to 39.7% of the control values. On the other hand, ethosuximide had no effect on AD generation at a concentration of 1 mM, which is clinically effective against absence seizures, but enhanced it at a toxic concentration of 10 mM. These findings indicate that the pharmacological profiles of antiepileptic drugs applied to our model correspond to those applied to seizures in patients with temporal lobe epilepsy. We therefore conclude that this model can be a useful in vitro model for the ictal manifestation of temporal lobe epilepsy.
Brain Research 02/2002; 924(1):39-45. · 2.73 Impact Factor
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ABSTRACT: Twenty patients with schizophrenia and ten normal control subjects underwent magnetic resonance imaging of the brain. The volumes of several brain structures were measured using a computer image analysing system. The schizophrenic patients had significantly smaller left parahippocampal volume and larger left temporal horn volume than the control subjects. A larger body of the right lateral ventricle could be estimated in the schizophrenics, but this difference was not significant. In the patient group a non-significant negative corrlation was established between the presence of positive symptoms and the left temporal horn volume. There was no signieficant correlation between the temporal horn and temporal lobe or medial temporal structures. Our results indicate that the left medial temporal structure or left temporal lobe may be involved in schizophrenia and that temporal horn enlargement does not simply represent volume loss of the surrounding tissue.
European Archives of Psychiatry and Clinical Neuroscience 03/1993; 242(5):268-272. · 3.49 Impact Factor
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ABSTRACT: To clarify the cognitive significance of event-related potential (ERP) abnormalities in schizophrenia, we examined the relationships of amplitudes and latencies of ERP components with performance on neuropsychological tests in schizophrenic patients. Twenty patients underwent the Trail Making B Test (TM-B), which is sensitive to frontal lobe dysfunction, and the logical memory, verbal paired-association, and visual reproduction subtests of the Wechsler Memory Scale (WMS), which are sensitive to temporal lobe dysfunctions, and ERP recordings during performance of an oddball auditory discrimination task. Pearson product–moment correlations indicated that an increased P200 amplitude was correlated with poor performance on the TM-B, whereas a decreased P300 amplitude was correlated with poor performance on the verbal paired-association subtest of the WMS. These findings suggest that a P200 abnormality represents the frontal lobe dysfunction, and a P300 abnormality represents the left temporal lobe dysfunction in schizophrenia.
International Journal of Psychophysiology.
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Masato Higashima,
Yasuhiro Kawasaki,
Katsumi Urata,
Yoshiki Maeda,
Naoto Sakai,
Chikako Mizukoshi,
Tatsuya Nagasawa,
Takahiro Kamiya,
Nariyoshi Yamaguchi,
Yoshifumi Koshino,
Hiroshi Matsuda,
Shiro Tsuji,
Hisashi Sumiya,
Kinichi Hisasda
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ABSTRACT: Reduced amplitude of the P300 component has been reported consistently in patients with neurological and psychiatric disorders. It is unclear, however, how such patients' cognitive dysfunction is related to their P300 abnormality. Further basic knowledge regarding neural substrates for P300 generation is required for gaining an understanding of the pathological significance of the P300 amplitude reduction. To determine the brain structures involved in P300 generation, we observed the event-related potential and the regional cerebral blood flow (rCBF) in 10 normal subjects performing an oddball discrimination of pure tones. The rCBF value was assessed quantitatively with the aid of single photon emission computed tomography using technetium-99m hexamethylpropylene amine oxime. During the task performance, significant activation was observed in the posterior superior temporal and inferior parietal regions of the right hemisphere. In addition, positive correlation of the task-related increase in rCBF with the simultaneously recorded P300 amplitude was observed in the right but not the left posterior superior temporal region. These findings indicate that activation of the right non-verbal auditory area might modulate P300 generation during pure-tone discrimination.
Cognitive Brain Research.
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ABSTRACT: Regional cerebral blood flow (rCBF) was measured with technetium-99m hexamethylpropyleneamine oxime single photon emission computed tomography in 38 neuroleptic-treated schizophrenic patients. To improve the validity of the evaluation of symptomatology, we applied findings previously derived in a principal component analysis (PCA) of the Positive and Negative Syndrome Scale. The PCA had disclosed five orthogonal independent symptom structures (i.e., negative, hostile/excited, thought disordered, delusional/hallucinatory, and depressive components), and obtained factor scores for 70 schizophrenic subjects, including the present sample. Stepwise regression analysis elucidated some of the cortical regions in which relative rCBF predicted the severity of symptoms—namely, lateral and orbital prefrontal, lateral temporal, inferior parietal, and medial temporal regions. Findings suggested that symptom structures derived from PCA could prove helpful in elucidating the pathophysiology of neural mechanisms.
Psychiatry Research: Neuroimaging.
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ABSTRACT: It has been hypothesized that a disruption of γ-aminobutyric acid (GABA) receptor-mediated processes may be involved in the pathophysiology of focal epilepsy. This disinhibition hypothesis has been postulated from the results of in vitro experiments of the interictal activity of focal epilepsy. Less is known, however, about how disinhibition may be involved in the production of the ictal activity. We therefore examined the pharmacological effects of selective agonists and antagonists of GABAA and GABAB receptors on ictal-like afterdischarges (ADs) induced following repetitive high-frequency electrical stimulation in the CA1 region of rat hippocampal slices. The GABAA receptor antagonist bicuculline (5 μM) fully blocked AD generation, as did the GABAA receptor agonist muscimol (2 μM), which is thought to produce a tonic inhibition during application. However, the benzodiazepine receptor agonist diazepam (5 μM), which enhances the inhibitory postsynaptic potential induced by synaptically released GABA, increased the number of spikes in the AD to 148.3% of the control value. On the other hand, the GABAB receptor antagonist phaclofen (1 mM) increased the number of spikes in the AD to 234.7% of the control value, while the GABAB receptor agonist baclofen (5 μM) reduced it to 46.9%. We therefore conclude that synaptic, but not tonic, activation of GABAA receptors appears to be necessary for ictal-like AD generation, while GABAB receptor activation plays a protective role. We therefore propose a modification to the simple disinhibition hypothesis.
Brain Research.
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ABSTRACT: To clarify the possible involvement of Ca2+ channel subtypes in epileptogenesis, the CA1 region of rat hippocampal slices was examined for the pharmacological effects of Ca2+ channel blockers on ictal-like afterdischarges (ADs) observed following the repetition of high-frequency electrical stimulation, as well as on interictal-like bursts of population spikes following single stimuli in the presence of bicuculline. Ni2+ and amiloride, which predominantly block T-type Ca2+ channels, suppressed the number of spikes in ADs at concentrations of these two channel blockers sufficient to eliminate this type of Ca2+ channel in acutely dissociated and cultured hippocampal neurons. On the other hand, neither the L-type Ca2+ channel blocker nifedipine nor the N-type Ca2+ channel blocker, ω-conotoxin GVIA had any effect on the generation of ADs. In addition, none of these T-, L- and N-type channel blockers had any effect on the bicuculline-induced, interictal-like epileptiform discharges. We therefore conclude that the activation of T-type Ca2+ channels, which is distinct from the mechanisms involved in interictal activity, may play a causative role in the generation of ictal-like ADs.
Brain Research.
