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The prevention of human error is an important task that has already been researched. Previous studies have shown that EEG signals can predict the occurrence of human errors. However, high accuracy has not yet been achieved in a single-trial analysis. This study is aimed to improve the accuracy of single-trial analysis, and propose a method for anomaly detection with auto encoder(AE). In the experiment, we conducted "Press the button(Go)" or "Do nothing(No-Go)" according to the visual stimulus and analyzed the EEG signal from -1000 ms to 0 ms when the stimulus was displayed. We prepared two types of inputs, time series data and frequency spectrum, and an AE was trained to reconstruct the inputs. We then calculated the difference between the reconstructed data and input data and predicted human error by its largeness. In the prediction using Support Vector Machine (SVM) based on the frequency spectrum, some over-fitting occurred and the average accuracy was 43 %. In the prediction using anomaly detection with frequency spectrum was 53 % and could not be classified. The time series data was 63 % which improved the accuracy. A previous study has shown frequency-dependent features such as -band activity and rhythm, as precursors of human error. However, in single-trial analysis, we obtained a higher accuracy by time series data than when by using the frequency spectrum. However, there was no noticeable difference between SVM and anomaly detection methods other than over-fitting. Therefore, in this case, the improvement in accuracy by the anomaly detection method could not be confirmed. However, the result suggests that it is more effective to use the frequency spectrum than the time series data in the single-trial analysis in the future.

When humans perform cognitive tasks, it is necessary to hold information temporarily. This is done by a brain function called working memory (WM). Since WM is active during the whole time range from stimulus presentation to task execution, onset detection is unnecessary, in contrast to readiness potentials for movement. Therefore, it is possible to realize application in a brain-computer interface (BCI) in various tasks without onset detection by performing single-trial classification of electroencephalogram (EEG) signals during WM. The purpose of this research was to examine the possibility of WM application to BCI. We classified the EEG signals during WM-time that required the retention of movement direction information when performing a right arm movement in order of two instructed sequential target directions using a 3-layer neural network (3-NN). In classification based on the signal immediately after presentation of 1st target (WM1), the classification accuracy was significantly higher (62%) than chance level (50%). In addition, the accuracy was higher when providing the phase of the fast Fourier transform to the classifier as information rather than the spectrum. However, it could not be classified by WM requiring the retention of information regarding two tasks (WM2). In summary, these results suggest a possibility that single trial classification of EEG during the first WM (WM1) is possible, and that the WM information is included mainly in the phase. Future studies should aim at improving the classification accuracy by using other feature quantities and classifiers, and to examine classification of EEG in tasks other than arm movement. Furthermore, the relationship between WM and EEG distribution also needs to be investigated.

From allowing basic communication to move through an environment, several attempts are being made in the field of brain-computer interfaces (BCI) to assist people that somehow find it difficult or impossible to perform certain activities. Focusing on these people as potential users of BCI, we obtained electroencephalogram (EEG) readings from nine healthy subjects who were presented with auditory stimuli via earphones from six different virtual directions. We presented the stimuli following the oddball paradigm to elicit P300 waves within the subject's brain activity for later identification and classification using convolutional neural networks (CNN). The CNN models are given a novel single trial three-dimensional (3D) representation of the EEG data as an input, maintaining temporal and spatial information as close to the experimental setup as possible, a relevant characteristic as eliciting P300 has been shown to cause stronger activity in certain brain regions. Here, we present the results of CNN models using the proposed 3D input for three different stimuli presentation time intervals (500, 400, and 300 ms) and compare them to previous studies and other common classifiers. Our results show >80% accuracy for all the CNN models using the proposed 3D input in single trial P300 classification.

Brain-machine interfaces (BMI) rely on the accurate classification of event-related potentials (ERPs) and their performance greatly depends on the appropriate selection of classifier parameters and features from dense-array electroencephalography (EEG) signals. Moreover, in order to achieve a portable and more compact BMI for practical applications, it is also desirable to use a system capable of accurate classification using information from as few EEG channels as possible. In the present work, we propose a method for classifying P300 ERPs using a combination of Fisher Discriminant Analysis (FDA) and a multiobjective hybrid real-binary Particle Swarm Optimization (MHPSO) algorithm. Specifically, the algorithm searches for the set of EEG channels and classifier parameters that simultaneously maximize the classification accuracy and minimize the number of used channels. The performance of the method is assessed through offline analyses on datasets of auditory ERPs from sound discrimination experiments. The proposed method achieved a higher classification accuracy than that achieved by traditional methods while also using fewer channels. It was also found that the number of channels used for classification can be significantly reduced without greatly compromising the classification accuracy.

Human error often becomes a serious problem in dairy life. Recent studies have shown that failures of attention and motor errors can be captured before they actually occur in the alpha, theta, and beta-band powers of electroencephalograms (EEGs), suggesting the possibility that errors in motor responses can be predicted. The goal of this study was to use single-trial offline classification to examine how accurately EEG signals recorded before motor responses can predict subsequent errors. Ten subjects performed a Go/No-Go task, and the accuracy of error classification by a Support Vector Machine (SVM) was investigated 1000 ms before presenting the Go/No-Go cue. The resulting mean classification accuracy was 62%, and strong increases and decreases in activities associated with errors were observed in occipital and frontal alpha-band powers. This result suggests the possibility that future errors can be predicted using EEG.

While motor imagery has been known as a powerful tool for neuro-rehabilitation in stroke patients, whether this technique is also effective for other brain disorders is unclear. For instance, patients with Parkinson's disease or attention-deficit hyperactivity disorder who are impaired at real motor switching may benefit therapeutically from training that consists of switching their imagined motor movements, and eventually recover from the dysfunction. However, despite its importance little is known about exactly how switching mental images of one's actions is processed in the brain. Therefore, we set out to clarify this issue by measuring brain activity reflected in electroencephalograms as subjects switched an imagined hand rotation from one hand to the other during a motor-imagery task. By comparing electroencephalogram signals from repeated mental imaging of hand movements, we found a switch-specific decrease in the beta-band activity in parietal and frontal regions around 0.6 s after stimulus presentation. Further, we found rotation-related negativity in the parietal cortex at the same time as the decreased beta-band power. These results suggest that the parietal area is dynamically involved in the switching of imagined hand motion, and that frontal areas may have an important role in inhibiting mental imagery of the deselected hand's motion.

Brain-Machine Interfaces (BMIs) are being researched controlling external devices such as robots and computers by measuring the cranial nerve activity of the operator. The brain activities evoked by visual stimuli have been studied intensively. However, few studies have considered a BMI that uses the brain activities evoked by auditory stimuli. This study investigated whether a person's direction of attention can be estimated using an event-related potential (ERP) generated by selective attention to an auditory stimulus. An auditory stimulus and an out-of-head sound localization system that can create an audio image outside the head that is presented through an earphone were used instead of a loudspeaker system. This system was experimentally evaluated by presenting the subject auditory cues from one of six directions while the subject directed his attention in one direction. An EEG response similar to an ERP was observed. The direction of attention was estimated using support vector machine with an accuracy of 89.2[%] on average for the three subjects. This suggests that a BMI system based on the estimated direction of attention can be developed by using out-of-head sound localization.

Objective: Multiscale entropy (MSE) is a recently proposed entropy-based index of physiological complexity, evaluating signals at multiple temporal scales. To test this method as an aid to elucidating the pathophysiology of Alzheimer's disease (AD), we examined MSE in resting state EEG activity in comparison with traditional EEG analysis., Methods: We recorded EEG in medication-free 15 presenile AD patients and 18 age- and sex-matched healthy control (HC) subjects. MSE was calculated for continuous 60-s epochs for each group, concurrently with power analysis., Results: The MSE results from smaller and larger scales were associated with higher and lower frequencies of relative power, respectively. Group analysis demonstrated that the AD group had less complexity at smaller scales in more frontal areas, consistent with previous findings. In contrast, higher complexity at larger scales was observed across brain areas in AD group and this higher complexity was significantly correlated with cognitive decline., Conclusions: MSE measures identified an abnormal complexity profile across different temporal scales and their relation to the severity of AD., Significance: These findings indicate that entropy-based analytic methods with applied at temporal scales may serve as a complementary approach for characterizing and understanding abnormal cortical dynamics in AD., (2010 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.)

Multiscale entropy (MSE) analysis is a novel entropy-based approach for measuring dynamical complexity in physiological systems over a range of temporal scales. To evaluate this analytic approach as an aid to elucidating the pathophysiologic mechanisms in schizophrenia, we examined MSE in EEG activity in drug-naive schizophrenia subjects pre- and post-treatment with antipsychotics in comparison with traditional EEG analysis. We recorded eyes-closed resting-state EEG from frontal, temporal, parietal, and occipital regions in drug-naive 22 schizophrenia and 24 age-matched healthy control subjects. Fifteen patients were re-evaluated within 2-8 weeks after the initiation of antipsychotic treatment. For each participant, MSE was calculated on one continuous 60-s epoch for each experimental session. Schizophrenia subjects showed significantly higher complexity at higher time scales (lower frequencies) than did healthy controls in fronto-centro-temporal, but not in parieto-occipital regions. Post-treatment, this higher complexity decreased to healthy control subject levels selectively in fronto-central regions, while the increased complexity in temporal sites remained higher. Comparative power analysis identified spectral slowing in frontal regions in pre-treatment schizophrenia subjects, consistent with previous findings, whereas no antipsychotic treatment effect was observed. In summary, multiscale entropy measures identified abnormal dynamical EEG signal complexity in anterior brain areas in schizophrenia that normalized selectively in fronto-central areas with antipsychotic treatment. These findings show that entropy-based analytic methods may serve as a novel approach for characterizing and understanding abnormal cortical dynamics in schizophrenia and elucidating the therapeutic mechanisms of antipsychotics., (Copyright (c) 2010 Elsevier Inc. All rights reserved.)

Objective: This study was intended to examine variations in electroencephalographic (EEG) complexity in response to photic stimulation (PS) during aging to test the hypothesis that the aging process reduces physiologic complexity and functional responsiveness., Methods: Multiscale entropy (MSE), an estimate of time-series signal complexity associated with long-range temporal correlation, is used as a recently proposed method for quantifying EEG complexity with multiple coarse-grained sequences. We recorded EEG in 13 healthy elderly subjects and 12 healthy young subjects during pre-PS and post-PS conditions and estimated their respective MSE values., Results: For the pre-PS condition, no significant complexity difference was found between the groups. However, a significant MSE change (complexity increase) was found post-PS only in young subjects, thereby revealing a power-law scaling property, which means long-range temporal correlation., Conclusions: Enhancement of long-range temporal correlation in young subjects after PS might reflect a cortical response to stimuli, which was absent in elderly subjects. These results are consistent with the general "loss of complexity/diminished functional response to stimuli" theory of aging., Significance: Our findings demonstrate that application of MSE analysis to EEG is a powerful approach for studying age-related changes in brain function.

We applied event-related potential (ERP) to reinforcement signals that are equivalent to reward and punishment signals.We conducted an electroencephalogram (EEG) in which volunteers identified the success or failure of a task. We confirmed that there were differences in the EEG depending on whether the task was successful or not and suggested that ERP might be used as a reward of reinforcement leaning. We used a support vector machine (SVM) for recognizing the P300. We selected the feature vector in SVM that was composed of averages of each 50 ms for each of the six channels (C3,Cz,C4,P3,Pz,P4) for a total of 700 ms. We can suggest that reinforcement learning using P300 can be performed accurately.

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.

Mental arithmetic (MA) tasks have been reported to induce an increase in blood pressure and heart rate by enhancing sympathetic activity. However, there are individual differences in the change of autonomic nervous activity during MA task. In the present study, we quantitatively analyzed EEG changes and autonomic nervous activity using heart rate variability (HRV) during MA task in 38 healthy young volunteers. They were classified into two groups, stress responders and non-responders, according to whether both LF/HF and blood pressure increased above the baseline or not in response to MA. Then autonomic and EEG changes were compared between the two groups. The MA task induced an increase in slow beta power in the stress responders, whereas it induced a decrease in slow beta power in the stress non responders. Further evaluation showed a significant positive correlation between the percent change from the baseline in slow alpha power and that in LF/HF. These results suggest that there are correlations between the autonomic response in an individual and EEG power changes during MA tasks.

Meditation is a specific consciousness state in which deep relaxation and increased internalized attention coexist. Autonomic nervous activity during meditation was reported to be characterized by decreased sympathetic activity and increased parasympathetic activity. And concerning EEG power, slow alpha power and fast theta power increased during meditation. On the other hand, mental arithmetic (MA) tasks have been reported to induce an increase in blood pressure and heart rate with enhanced sympathetic activity. However, changes in autonomic nervous activity and EEG power during MA tasks and their mutual relationship have not been adequately studied. In the present study, we quantitatively analyzed the changes in autonomic nervous activity using heart rate variability (HRV) and EEG power during MA task in 30 healthy volunteers. MA task induced significant increases in normalized LF, LF/HF ratio (as a sympathetic index), and a decrease in normalized HF (as a parasympathetic index). On the other hand, significant decrease in EEG power (slow theta: 4-6 Hz and fast alpha: 10-13 Hz in the posterior region and fast theta: 6-8 Hz and slow alpha: 8-10 Hz in all the regions) were induced by MA task. Further evaluation of these changes showed a negative correlation between the change rates (with the control resting condition as the baseline) in fast alpha power and that in LF/HF. These results suggest that specific correlated relationships exist between the change in autonomic nervous activity and EEG power depending on the difference in mental task (i.e., meditation or MA).

Meditation is the attainment of a restful yet fully alert physical and mental state practiced by many as a self-regulatory approach to emotion management, but the psychophysiological properties and personality traits that characterize this meditative state have not been adequately studied. We quantitatively analyzed changes in psychophysiological parameters during Zen meditation in 20 normal adults, and evaluated the results in association with personality traits assessed by Cloninger's Temperament and Character Inventory (TCI). During meditation, increases were observed in fast theta power and slow alpha power on EEG predominantly in the frontal area, whereas an increase in the normalized unit of high-frequency (nuHF) power (as a parasympathetic index) and decreases in the normalized unit of low-frequency (nuLF) power and LF/HF (as sympathetic indices) were observed through analyses of heart rate variability. We analyzed the possible correlations among these changes in terms of the percent change during meditation using the control condition as the baseline. The percent change in slow alpha EEG power in the frontal area, reflecting enhanced internalized attention, was negatively correlated with that in nuLF as well as in LF/HF and was positively correlated with the novelty seeking score (which has been suggested to be associated with dopaminergic activity). The percent change in fast theta power in the frontal area, reflecting enhanced mindfulness, was positively correlated with that in nuHF and also with the harm avoidance score (which has been suggested to be associated with serotonergic activity). These results suggest that internalized attention and mindfulness as two major core factors of behaviors of mind during meditation are characterized by different combinations of psychophysiological properties and personality traits.

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., (Copyright (c) 2005 S. Karger AG, Basel.)

To investigate sequential changes in electroencephalograms (EEGs) during intermittent photic stimulation (IPS), quantitative EEG analysis for the alpha band (related to stimulus frequency) was performed in 18 drug-naïve schizophrenic patients and 18 sex- and age-matched control subjects. IPS consisted of white flickers at 10 flashes/sec, lasting 10 sec and repeated six times at 10 sec intervals. The differences between the two groups were assessed for two conditions (i.e., during photic stimulation (PS) and inter-PS). During stimulus, the absolute 9-11 Hz band power of the patient group was higher at the posterior than that at the anterior sites throughout the 10 sec periods. However, this difference between sites was not seen during the first 1 sec in the control group. During the nonstimulus period, posterior dominance of 9-11 Hz band power was prominent in the patient group throughout. In the control group, however, this difference was minor, especially during the latter half of the period. These results suggest that schizophrenic patients show fewer changes in posterior alpha activity during both stimulus and nonstimulus, and this continuity of posterior dominance may reflect hyperarousal, which counteracts any decrease in vigilance throughout the IPS.

Objectives: The distinction between electroencephalogram (EEG) driving responses in normal aging and Alzheimer's disease (AD) is unclear. This study was conducted to explore the structure of harmonic responses of EEG coherence during photic stimulation (PS) in AD., Methods: EEG interhemispheric coherence was analyzed for each harmonic responses during PS (white flickers at 5, 10 and 15 flashes/sec) in younger subjects (20-25 years), non-demented elderly subjects (50-67 years) and AD patients (43-66 years)., Results: The elderly subjects had higher interhemispheric coherence during PS than the younger subjects, with significant differences found in the 6th (30Hz) and 8th (40Hz) harmonic responses to 5Hz PS. The AD patients had significantly smaller coherence than the elderly subjects in the 2nd (10Hz) and 4th (20Hz) harmonic responses to 5Hz PS, and in the fundamental (10Hz) and 2nd (20Hz) harmonic responses to 10Hz PS. These coherence values did not correlate with duration of the disease or with cognitive functioning as evaluated by MMSE score., Conclusions: A failure of stimulation-related brain activation in AD patients was observed in alpha-related frequencies, suggesting that AD is not the end result of normal aging of the brain, at least in terms of the mechanisms which are involved in PS-related functional organization.

In order to investigate whether Alzheimer's disease (AD) is the end result of aging of the brain or the result of some other mechanism, we analyzed EEGs showing the absolute power of harmonic responses to photic stimulation (PS) in younger subjects, non-demented elderly subjects and AD patients. At rest, the AD patients generally showed less absolute power than the younger and elderly subjects, with significant differences found at 10 Hz and 20 Hz. Analysis of EEGs recorded during PS indicated that the elderly subjects generally demonstrated more absolute power than the younger subjects and AD patients. These findings suggest a failure of stimulation-related brain activation in AD patients, and provide further evidence that normal aging and AD employ different mechanisms for functional organization during PS.

Our study was designed to investigate the influence of alcohol on sleep using the correlation dimension (D2) analysis. Polysomnography (PSG) was performed in 10 adult human males during a baseline night (BL-N) and an ethanol (0.8 g/kg body weight) night (Et-N). The mean D2 values during the Et-N and BL-N decreased significantly from wakefulness to stages 1, 2, and 3+4 of nonrapid eye movement (non-REM) sleep, and increased during REM sleep. The mean D2 of the sleep electroencephalogram (EEG) during stage 2 during the Et-N was significantly higher than during BL-N. In addition, the mean D2 values of the sleep EEG for the second, third and fourth sleep cycles during the Et-N were significantly higher than during the BL-N. These significant differences between BL-N and Et-N were not recognized by spectral and visual analyses. Our results suggest that D2 is a potentially useful parameter for quantitative analysis of the effect of ethanol on sleep EEGs throughout the entire night., (Copyright 2002 S. Karger AG, Basel)

We previously introduced the manual zero potential shifting (MZPS) method into dipole analysis to reduce the influence by error potential at the analytical stage. The source localizations of epileptic spikes as an equivalent current dipole (ECD) were estimated in a patient with symptomatic epilepsy and contrasted with findings obtained by magnetic resonance imaging (MRI) and single photon emission computed tomography (SPECT). When spikes were analyzed by the MZPS method, ECDs had high values of dipolarity, an indicator of ECD reliability. Moreover, their locations corresponded with lesions shown by MRI and SPECT. When the same spikes were analyzed by the conventional method, dipolarity values were declined and the locations did not correspond with lesions. These results provide further evidence that the MZPS method is of clinical utility in evaluating the electric source generator of epileptic spikes.

Sleep electroencephalograms (EEG) were analyzed by non-linear analysis. Polysomnography (PSG) of nine healthy male subjects was analyzed and the correlation dimension (D2) was calculated. The D2 characterizes the dynamics of the sleep EEG, estimates the degrees of freedom, and describes the complexity of the signal. The mean D2 decreased from the awake stage to stages 1, 2, 3 and 4 increased during rapid eye movement (REM) sleep. The D2 during each REM sleep stage were high and those during each slow wave sleep stage were low, respectively, for each sleep cycle. The mean D2 of the sleep EEG in the second half of the night was significantly higher than those in the first half of the night. Significant changes were also observed during sleep stage 2, but were not seen during REM sleep and sleep stages 3 and 4. The D2 may be a useful method in the analysis of the entire sleep EEG.

The influence on sleep of alcohol (ethanol) was investigated in nine males using the correlation dimension (CD). Polysomnography (PSG) was recorded on a baseline night (BL-N) and on an ethanol (0.8 g/kg) night (Et-N). The mean correlation dimensions on Et-N, as well as on BL-N, significantly decreased from sleep stage 'awake' to sleep Stages 1, 2 and 3 and increased during rapid eye movement (REM) sleep. The mean correlation dimensions of the sleep EEG during sleep Stage 2 and those for the second sleep cycle on the Et-N were significantly higher than those on the BL-N. The changes in the correlation dimensions between sleep cycles were reduced on Et-N as compared to BL-N.

The present study was conducted to examine and compare interhemispheric EEG coherence at rest and during photic stimulation (PS; 5, 10 and 15 Hz) in 30 younger subjects aged 22.1 +/- 2.2 (mean +/- S.D.) and 25 elderly subjects aged 56.8 +/- 4.9. The elderly subjects had significantly lower coherence in the resting EEG for the delta, theta, alpha-3, beta-1 and beta-2 frequency bands. In contrast, EEG analysis during PS showed that elderly subjects had significantly higher coherence in the frequency corresponding to PS at 15 Hz. In addition, when we examined the changes in coherence from the resting state to the stimulus condition (i.e., coherence reactivity), elderly subjects had significantly higher coherence reactivity to PS at 15 Hz. These findings suggest a low interhemispheric functional connectivity in elderly subjects under non stimulus conditions and a high connectivity during photic stimulus.

The present study of coherence analysis, in 16 healthy male volunteers, aged 24-31 years, showed that the administration of 0.25 mg of scopolamine significantly reduced interhemispheric coherence in the delta and beta-1 bands in the resting state. Scopolamine also caused a significant increase both in EEG coherence during PS and in PS-related coherence reactivity in the beta band. In addition, this compound significantly reduced total WMS scores. These findings suggest that, in addition to causing cognitive impairments, central cholinergic dysfunction can alter interhemispheric functional connectivity under both nonstimulus and stimulus conditions.

This study examined the effects of the anticholinergic drug, scopolamine (0.25 mg) in 16 right-handed healthy volunteers. EEGs were recorded before and 60 min after intramuscular administration, and spectral analysis was performed on EEGs recorded at rest and during photic stimulation. Each subject was also evaluated by the Wechsler Memory Scale (WMS; form 1 or 2) before and 90 min after drug administration. In the resting EEG, the scopolamine administration resulted in a significant increase in the absolute power on the delta band (2.0- 3.8 Hz) and in the relative power on the delta and theta-1 bands (4.0-5.8 Hz) mainly over the central and parieto-occipital regions. In contrast, scopolamine significantly decreased the relative alpha-2 band (9.2-12.8 Hz) power mainly over the frontal regions and the absolute alpha-2 band power at most of the recording sites. The analysis of stimulus data showed that scopolamine significantly decreased fundamental photic driving responses elicited by photic stimulation at 15 Hz, with significant effects confined to the occipital regions. These EEG changes occurred in association with a significant reduction in total WMS scores as well as in scores of logical and visual memory subtests. These findings suggest that, in addition to cognitive impairments, central cholinergic dysfunction can cause EEG changes under both nonstimulus and stimulus conditions.

To clarify the electroencephalographic characteristics of mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes (MELAS), the medical records and electroencephalograms of six patients with MELAS and two of their relatives with MELA (mitochondrial myopathy, encephalopathy, and lactic acidosis, without strokelike episodes) were retrospectively reviewed. All have a point mutation in the mitochondrial DNA at nucleotide position 3243. The electroencephalograms (n = 79) were divided into four groups according to the time relation to the strokelike episode: (1) before the first strokelike episode, (2) within 5 days after the strokelike episode (acute stage), (3) between 6 days and 1 month after the strokelike episode (subacute stage), and (4) more than 1 month after the strokelike episode (chronic stage). In the acute stage, 10 of the 11 electroencephalograms (9 strokelike episodes in four patients) revealed focal high-voltage delta waves with polyspikes (FHDPS), which were recognized as ictal electroencephalogram. Ictal events during FHDPS included focal clonic or myoclonic seizure and migrainous headache. In the subacute and chronic stages, focal spikes or sharp waves and 14- and 6-Hz positive bursts were frequently recorded. The authors' results suggest that FHDPSs present a reliable and accurate indicator of a strokelike episode in patients with MELAS.

The dipole tracing method is a technique whereby an electric source generator is estimated as an equivalent current dipole (ECD) based on potential distribution on the scalp. To estimate the electric source generator of low amplitude spikes, a manual zero potential shifting (MZPS) method was introduced in which a zero potential is set manually in dipole analysis. The subjects were three patients with localization-related epilepsy with temporal spikes. When low-amplitude spikes (< 50 microV) were analyzed by the conventional mean zero potential method, the dipolarity, an indicator of ECD reliability, had a low value and its locations were scattered. In contrast, when these low-amplitude spikes were analyzed by the MZPS method, ECD showed a high dipolarity value comparable to that obtained when high-amplitude spikes (> or = 50 microV) were analyzed by the mean zero potential method. Furthermore, the locations of the former ECD tended to converge and were almost identical to those of the latter ECD. These findings suggest the usefulness of the MZPS method in dipole analysis in terms of the dipolarity and ECD locations of low-amplitude spikes.

We assessed functional relationships between hemispheres by calculating interhemispheric EEG coherence at rest and during photic stimulation in 18 never-medicated patients with paranoid schizophrenia and 30 control subjects. Although no significant group differences were found in the resting EEG, the schizophrenic patients had significantly higher coherence on EEGs recorded during photic stimulation, compared to the control subjects. In this study, we also examined the changes in interhemispheric coherence from rest to the stimulus condition (i.e., stimulation-related coherence reactivity); the patients were found to show significantly greater coherence reactivity to photic stimulation. These findings provide further evidence that schizophrenic patients have a higher degree of interhemispheric functional connectivity and thus have less lateralized cerebral organization than normal subjects. Our results also suggest that schizophrenic patients have excessive functional reorganization between hemispheres in association with photic stimulation.

The present study was conducted to examine interhemispheric electroencephalogram (EEG) coherence at rest and during photic stimulation (5, 10, and 15 Hz) in 10 patients with presenile dementia of the Alzheimer type (AD; mean age at onset, 56 years) and 10 sex- and age-matched control subjects. Compared with the control subjects, the AD patients had significantly lower interhemispheric coherence in the resting EEG for the delta, theta-2, alpha, and beta-1 frequency bands. EEG analysis during photic stimulation also showed that the patients had significantly lower coherence, irrespective of the stimulus frequency. In addition, when we examined the changes in coherence from the resting state to the stimulus condition (i.e., coherence reactivity), significant group differences were found at the brain region primarily involved in visual functioning; the patients had significantly smaller coherence reactivity to photic stimulation at 5 and 15 Hz over the posterior regions. These findings suggest that AD patients have an impairment of interhemispheric functional connectivity in both nonstimulus and stimulus conditions. The findings also suggest a failure of normal stimulation-related brain activation in AD.

Electroencephalography (EEG) coherence provides a measure of functional correlations between two EEG signals. The present study was conducted to examine intrahemispheric EEG coherence at rest and during photic stimulation (PS; 5, 10 and 15 Hz) in ten unmedicated patients with presenile dementia of the Alzheimer type (AD; mean age at onset 56 years). In the resting EEG, the AD patients had significantly lower coherence than gender- and age-matched control subjects in the alpha-1, alpha-2 and beta-1 frequency bands. The EEG analysis during PS also showed that the patients had significantly lower coherence in the frequency corresponding to PS at 10 and 15 Hz. In this study, the changes in coherence from the resting state to the stimulus condition (i.e. PS-related coherence reactivity) were examined. The patients were found to show significantly smaller coherence reactivity to PS at 5 and 15 Hz. These findings suggest that, in addition to the resting state, AD patients have an impairment of intrahemispheric functional connectivity during PS. They also suggest that AD shows a failure of PS-related functional reorganization.

EEG coherence provides a measure of functional correlations between two EEG signals. The present study was conducted to examine intrahemispheric EEG coherence at rest and during photic stimulation (PS) in 18 drug-naive patients with paranoid schizophrenia and 30 control subjects. Compared with the controls, the schizophrenic patients had significantly higher intrahemispheric coherence of the resting EEG for the delta band, although no significant group differences were found for other frequency bands. EEG analysis during PS showed that the patients also had significantly higher EEG coherence over the left posterior regions. In this study, we also examined the changes in intrahemispheric coherence from rest to the stimulus condition (i.e., PS-related coherence reactivity); the patients were found to show significantly smaller changes, with significant group differences being also confined to the posterior regions in the left hemisphere. These findings provide evidence that schizophrenic patients have abnormal EEG coherence in both resting and stimulus conditions and suggest more diffuse, undifferentiated functional organization within hemispheres. In addition, diminished coherence reactivity suggests a failure of PS-related functional reorganization in schizophrenia.

Topographic analysis of the resting EEG was performed in nine patients with presenile Alzheimer's disease(AD) and nine sex- and age-matched normal subjects. We also analyzed EEG activity recorded during photic stimulation(5, 10 and 15 Hz) to evaluate photic driving responses. The square root of absolute power was determined for each frequency band using a Fast Fourier Transform. Compared with the controls, the AD patients had increased delta and theta in the resting EEG mainly over the frontal regions. The patients also had reduced alpha and beta, and did not show posterior predominance of alpha activity. EEG analysis during photic stimulation showed that the patients had a reduction in photic driving responses, and significant topographic differences were found over the parieto-occipital regions. These findings provide further evidence that AD patients have background EEG slowing with a reduction in alpha and fast activity. They also suggest an impairment of visual functioning in AD.

In the present study, quantitative electroencephalographic (EEG) analysis was performed at rest and during photic stimulation (5, 10, and 15 Hz) in nine patients with presenile dementia of the Alzheimer type (AD; mean age at onset, 55 years) and nine sex- and age-matched control subjects. Compared with the normal controls, the AD patients had a significantly lower alpha-2 and beta band power in the resting EEG as well as a significant increase in delta and theta band power. EEG analysis during the photic stimulation demonstrated that the AD patients had a significantly lower EEG power during photic stimulation for the alpha (9.8-10.2 Hz) and beta bands (14.8-15.2 Hz) corresponding to photic stimulation at 10 Hz and 15 Hz, respectively. In addition, when we examined EEG changes from rest to the stimulus condition, the AD patients were found to show significantly smaller changes in EEG power mainly over the posterior regions, irrespective of the stimulus frequency. These findings provide evidence that AD patients have EEG abnormalities in both non-stimulus and stimulus conditions, and suggest diminished EEG reactivity to photic stimulation.

The present study was conducted to examine sex differences in interhemispheric EEG coherence in 15 male and 15 female healthy young adults. EEG was recorded during rest and photic stimulation (PS) at 5, 10 and 15 Hz using a linked earlobe reference. Interhemispheric coherence of the resting EEG revealed no significant sex-related differences for any frequency band. In contrast, significant sex-related differences were found in EEG coherence during PS; the females had a significantly higher coherence than the males for F3-F4 and C3-C4 in the frequency band (4.5-5.5 Hz) corresponding to 5 Hz PS. In addition, the changes in interhemispheric coherence from rest to the stimulus condition (i.e. PS-related coherence reactivity) showed sex-related differences at the brain region primarily involved in visual functioning; the females had significantly greater coherence reactivity for O1-O2 in EEG during PS at 5 and 15 Hz. These findings indicate sex-related differences in interhemispheric EEG coherence during PS, and support the well-demonstrated evidence that sex differences exist in the degree of lateralization of cerebral function.

The present study was conducted to examine inter- and intrahemispheric EEG coherence in 14 healthy, right-handed adults during wakefulness and light drowsiness as assessed by eye movement and EEG activity. Interhemispheric coherence was significantly lower during light drowsiness than during wakefulness for O1-O2 in the alpha-1 band and for F3-F4 in the beta-1 band. Intrahemispheric EEG coherence was significantly higher during light drowsiness for C4-O2 in the theta-1 and beta-1 bands. These findings indicate that light drowsiness can alter both inter- and intrahemispheric EEG coherence when compared with wakefulness, suggesting that cerebral functional organization changes during light drowsiness. It is important, therefore, to control arousal level of subjects in future studies dealing with the relationship between EEG coherence and various pathological conditions.

EEG coherence is a noninvasive technique for studying functional relationships between brain regions. Although EEG coherence would be a useful method to explore the differences in cerebral functional organization between the sexes, sex differences in coherence have not been well documented. The present study was conducted therefore to examine sex differences in interhemispheric EEG coherence during rest and photic stimulation (PS) in 15 male and 15 female healthy young adults. Interhemispheric coherence of the resting EEG revealed no significant sex differences for any frequency band. In contrast, coherence during PS revealed significant sex differences, and the females had a significantly higher coherence than the males in the frequency band (4.5-5.5Hz) corresponding to 5Hz PS. In addition, the changes in interhemispheric coherence from rest to the stimulus condition (i.e., coherence reactivity) showed sex differences at the brain region primarily involved in visual functioning; the females had significantly greater coherence reactivity for O1-O2 in EEG during PS at 5 and 15Hz. These findings indicate sex differences in interhemispheric EEG coherence during PS, and provide further evidence that sex-related differences exist in the degree of lateralization of hemispheric function.

Amygdala-kindled kittens exhibit frequent epileptiform EEG transients, often in conjunction with phasic arousal events of sleep [k-complexes, pontogeniculo-occipital (PGO) waves, and/or sleep spindles]. In this study, paroxysmal microarousals occurred throughout the sleep-wake cycle after kindling, but were most frequent during seizure-prone states of slow-wave sleep (SWS) and the transition into rapid-eye-movement sleep (REM). Their incidence correlated with interictal sleep fragmentation as well as onset of spontaneous convulsions. Results could reflect transsynaptic kindling effects on brainstem and forebrain arousal mechanisms with which amygdala is reciprocally connected. Increased discharge rates of neural generators for normal EEG and behavioral arousal could disrupt sleep at some times and recruit epileptic neurons in the kindled focus to precipitate seizures at others. Alternatively, epileptiform EEG paroxysms were accompanied by subtle behavioral stereotypes (a head nod, limb elevation, eye twitch, lip smack, or a combination of these). Behavioral correlates were elements of partial kindled seizures, suggesting that paroxysmal microarousals may be subclinical seizures. Whether or not the microarousals are true seizures, our findings may link ictal onset and interictal sleep disorders to a subclinical paroxysmal arousal disorder and suggest a common epileptic mechanism.

The present study performed quantitative EEG analysis in normal 20 males and 20 females, aged 18-26 years, in order to examine the sex differences in EEG activity at rest. The females had more absolute EEG power than the males, with significant differences observed for delta, theta and beta bands. In contrast, no significant difference was found in peak alpha frequency or relative EEG power for any frequency band. The present findings provide further evidence that females have more absolute power in resting EEG, and emphasize the importance of matching patients and control populations for sex in future investigations dealing with the relationship between resting EEG and various pathological conditions.

The present study was conducted to compare electroencephalogram (EEG) driving responses to 10 hertz photic stimulation in 14 drug-naive schizophrenia patients and 16 sex- and age-matched control subjects. The amplitude of photic driving responses (PDRs) recorded from the occipital region was significantly lower in schizophrenia patients than in controls. In eight schizophrenia patients (vs. none in the control group) the PDR amplitudes recorded at the frontal region were higher than those at the occipital region, and frontal to occipital PDR ratios were significantly larger in schizophrenia subjects than in controls. Quantitative analysis of the resting EEG showed that the patients also had a significantly lower amplitude for the alpha frequency band. These findings suggest that the PDRs of schizophrenia patients are abnormal in their amplitude and distribution.

In this study we performed quantitative EEG analyses in 12 drug-naive patients who fulfilled DSM-IIIR criteria for schizophrenia and in a group of 12 healthy subjects. The schizophrenic patients were found to have slower activity (delta and theta) than the controls. These differences were most marked in the frontal region for delta band and in the occipital region for theta band. The schizophrenic patients also had more beta 1 activity, particularly in the occipital leads. Conversely, they had less alpha 2 activity over all regions examined. Our findings indicate cerebral dysfunction in schizophrenia and are in line with the hypothesis of hypofrontality in this disorder.

In the present study quantitative EEG analysis was performed in 20 male and 20 female healthy adults in order to examine the gender differences in EEG activity at rest and during photic stimulation. The females generally showed a higher amplitude in the resting EEG than the males, with significant differences observed for the delta, theta, alpha 2 and beta bands at the limited electrode sites. The gender differences were more pronounced in EEG activity during photic stimulation, and the females had a higher EEG amplitude in the frequency band identical or harmonically related to the stimulus frequency. These findings provide further evidence that the gender differences exist in EEG activity in both stimulus and nonstimulus conditions.

In the present study, quantitative EEG analysis was performed at rest and during 10 Hz photic stimulation in 14 drug-naive patients with first-episode paranoid schizophrenia and 20 sex- and age-matched control subjects. Compared with the normal controls, the patients had significantly lower alpha-2 band amplitude in the resting EEG over all recording regions. No significant group differences were found in other frequency bands. In addition, EEG analysis during photic stimulation demonstrated that the patients had a rather uniform topographic profile in EEG amplitude for the alpha band, with significant group differences being confined to the posterior regions in the left hemisphere. There were no significant group differences in the amplitude for the frequency bands harmonically related to the stimulus frequency. These findings provide further evidence that schizophrenic patients have abnormal EEG activity in both non-stimulus and stimulus conditions, and suggest a dysfunction in the mechanisms underlying EEG alpha generation in schizophrenia.

The effects of a serotonin (5-HT) receptor agonist, 5-methoxy-N,N-dimethyltryptamine (5-MeODMT), on epileptic photosensitivity were studied in the lateral geniculate-kindled cat. 5-MeODMT at 4 mg/kg significantly suppressed photically induced myoclonus, but not paroxysmal EEG activity, at 0.5-1 h after injection. This antiepileptic effect was seen in association with the appearance of behavioral signs similar to those seen in the 5-HT syndrome. The present data provide further evidence that 5-HT plays an important role in photosensitive epilepsy, and suggest that the inhibitory effect of 5-MeODMT on photosensitivity results from its agonist action at 5-HT1 receptors.

This study assessed the effects of MK-801 (0.1 and 0.5 mg/kg), a noncompetitive antagonist of N-methyl-D-aspartate receptors, on focal seizure activity elicited by electrical stimulation to the feline hippocampus. Neither afterdischarge duration nor behavioral seizure stage was significantly suppressed following intraperitoneal administration of MK-801 at two dose. Rather, MK-801 at a higher dose induced hippocampal seizure status in some of the cats tested. The present data suggest convulsant properties of MK-801 and limitations of its clinical utility as an antiepileptic agent.

Kindling of the primary visual cortex (VC) was compared with that of the amygdala in cats. VC kindling was basically similar to kindling of the amygdala in that daily electrical stimulation can lead to the development of a generalized convulsion in most subjects, a growth of afterdischarges in their configuration and duration, and a reduction of the afterdischarge threshold. The kindling response of the VC differed from that of the amygdala in a number of respects, i.e., a high afterdischarge threshold, a different pattern of behavioral seizure development, an abrupt growth of electroclinical seizures coincident with the onset of a generalized convulsion, an intersubject variability in seizure susceptibility, and a marked seizure instability. In VC kindling the afterdischarge propagation into the amygdala was not observed until the generalized convulsion developed, and the early involvement of afterdischarge was seen in the pulvinar, lateral geniculate body, and superior colliculus. These data suggest that a neural mechanism different from amygdaloid kindling may participate in VC kindling, and that the subcortical structures of the visual system are involved in the preferential pathway for a seizure generalization from the VC.