Computerized EEG in schizophrenic patients

We undertook a study of electroencephalograms (EEGs) in 30 right-handed, untreated patients (27.3 +/- 10.0 years; hebephrenic, 16; paranoid, 12; residual, 2) who fulfilled ICD-9 criteria for schizophrenia and compared them with sex- and age-matched controls by using the percentage of power in six EEG frequency bands calculated as a fraction of total power. T-statistic significance probability mapping (t-SPM) showed that, compared with normal controls, schizophrenics had more slow activity (delta, theta, and alpha 1) in the parieto-occipital regions, and more fast activity (beta 1) in the occipital regions. In contrast, alpha 2 activity decreased strikingly in the occipital regions and this decreased activity extended over much of the head. These findings were thought to indicate both cerebral hypofunction and excitability in acute untreated schizophrenia.     

Abnormal EEG patterns in treatment-resistant schizophrenic patients.

This study was conducted in order to compare the EEG patterns of schizophrenics who do not respond to typical neuroleptics with those who do respond under typical neuroleptic medication and a group of controls. Absolute (AP) and relative power (RP), and inter- and intrahemispheric correlations were calculated. Nonresistant schizophrenics showed lower delta RP, higher alpha 1 AP and RP and higher correlation between prefrontal areas than the resistant ones and controls. Resistant schizophrenics showed lower alpha 2 RP, lower beta 1 and beta 2 in temporal but higher beta 2 AP and RP in occipital derivations, and higher intrahemispheric correlation between Fp2 and F4 and lower between F8 and T4 than the nonresistant and controls. The resistants also showed a higher antero-posterior beta 1 and beta 2 index than the controls. We concluded that the EEG pattern showed by the nonresistants may be associated with their good neuroleptic response that was not present in the resistant schizophrenics.     

Differences of cerebral lateralization among schizophrenic and depressed patients.

Conjugate lateral eye movements (LEMs) have been used as a measure of contralateral frontal hemisphere activation when individuals carry out reflective tasks. In a previous study, schizophrenics were noted to produce significantly more R-LEMs than controls suggesting that they use the left hemisphere in general more often than controls when initiating thought. More specifically, schizophrenics initiated thought on spatial emotional material in their left hemisphere more often than normals. In an effort to replicate these findings, the present study contrasted a new sample of 13 schizophrenics first with the original schizophrenic sample, and then with 13 psychotic depressives, and the original controls. In addition, other group comparisons are reported. The data obtained replicate the original findings of increased R-LEM (i.e., increased left hemisphere activity) and the excessive processing of spatial and to a lesser extent emotional material in the left hemisphere of schizophrenics. Psychotic depressives were found to initiate reflective tasks more often in their right hemisphere than either schizophrenic or the original sample of normal controls. Significant group differences among schizophrenics, normal controls, and psychotically depressed patients were obtained. The data are consistent with emerging concepts of a left hemisphere locus of disturbance in schizophrenia and right hemisphere disturbances in affective disorders.     

EEG coherence in unmedicated schizophrenic patients

We have recently shown that electroencephalogram (EEG) coherence data recorded with common reference methods, including those obtained from schizophrenics, are confounded by power and phase effects. Three published reports using bipolar recordings found that EEG coherence was higher in schizophrenics; however, only medicated patients were studied. To extend these findings, we measured EEG coherence from bipolar EEG recordings in unmedicated schizophrenics (n = 10), affective disorder patients (n = 8), and normal controls (n = 13) during resting and task conditions. Seven schizophrenics were restudied after a period of neuroleptic treatment. Schizophrenics had higher across-task interhemispheric (p less than 0.05) and intrahemispheric (p less than 0.04) coherence in the theta band and tended to have higher intrahemispheric alpha coherence (p less than 0.08). Medication treatment was associated with clinical improvement and increases in spectral power, but not with changes in coherence values. These results confirm those obtained by earlier investigations and suggest that increased coherence reflects the presence of anomalous cortical organization in schizophrenics rather than medication effects or transient states related to acute clinical disturbance.     

EEG in schizophrenic patients: mutual information analysis.

OBJECTIVE: The aim of the present study is to assess information transmission between different cortical areas in schizophrenics by estimating the average cross mutual information (A-CMI) and to characterize the dynamical property of the cortical areas of schizophrenic patients from multi-channel EEG by establishing the auto mutual information (AMI). METHODS: We recorded the EEG from 16 electrodes in 10 schizophrenic patients and 10 age-matched normal controls. We estimated the slope of the AMI to evaluate the complexity of the EEG signal from one electrode and the A-CMI values of all 16x16 pairs of electrodes were calculated to investigate the information transmission of different cortical areas in schizophrenic patients. RESULTS: In T5 and C3 electrodes, the schizophrenic patients had lower complexity than normal controls. The schizophrenic patients had significantly higher interhemispheric and intrahemispheric A-CMI values than the normal controls. CONCLUSIONS: These results are consistent with previous findings that suggest left hemispheric hypotemporality and inter- and/or intra-hemispheric overconnectivity in schizophrenics. Our results of the left hemispheric hypotemporality and the increased interhemispheric information transmission in temporal lobe may support the hypothesis that the abnormal laterlization in temporal lobe are due to left temporal lobe deficit in schizophrenic patients.     

Negative symptoms and EEG alpha activity in schizophrenic patients.

Quantitative analyses of electroencephalographic (EEG) recordings in schizophrenic patients have often demonstrated reduced alpha band (8-13 Hz) activity. However, this finding is not universal and there is some evidence that subgroups of schizophrenics may differ in overall or lateralized levels of EEG alpha activity. To investigate this issue, the authors examined relationships between clinical ratings performed at the time of EEG recording and resting alpha power and coherence in 14 medication free schizophrenic patients. Nine channels of previously recorded resting (eyes open) EEG were transformed to average reference prior to spectral analysis and transformed to source derivation prior to calculation of inter-electrode coherences. Patients were rated with the Brief Psychiatric Rating Scale (BPRS), from which subscales corresponding to negative symptoms, positive symptoms, paranoia, and anxiety/depression were derived. Ratings and EEG measures were also obtained on 10 of the schizophrenic patients after neuroleptic treatment. Multiple regression with repeated measures was used to examine the influence of the subscale scores on bilateral log alpha power and both within- and between-hemisphere alpha coherence at selected locations. Prior to treatment, negative symptoms varied inversely with alpha power (p < 0.02), within-hemisphere alpha coherence (p < 0.03), and between-hemisphere coherence (p = 0.053). The effect of negative symptoms on alpha power was bilateral, but the effect on within-hemisphere coherence tended (p = 0.053) to be right-sided. After treatment these relationships were no longer present. The possible implications of and the effects of drug treatment on an association between negative symptoms and reduced alpha activity are discussed.     

Detection of non-linearity in the EEG of schizophrenic patients.

OBJECTIVE: The aim of this study is to detect non-linearity in the EEG of schizophrenia with a modified method of surrogate data. We also want to identify if dimension complexity (correlation dimension using spatial embedding) could be used as a discriminating statistic to demonstrate non-linearity in the EEG. The difference between the attractor dimension of healthy subjects and schizophrenic subjects is expected to be interpreted as reflecting some mechanisms underlying brain wave by views of non-linear dynamics analysis may reflect mechanistic differences. METHODS: EEGs were recorded with 14 electrodes in 18 healthy male subjects (average age: 26.3; range: 20--35) and 18 male schizophrenic patients (average age: 30.6; range: 24--40) during a resting eye-closed state. Neither of two groups was taking medicines. All artificial epochs in the EEG records were rejected by an experienced doctor's visual inspection. RESULTS: Testing non-linearity with modified surrogate data, we showed that correlation dimension of EEG data of schizophrenia does refuse the null hypothesis that the data were resulted from a linear dynamic system. A decrease of dimension complexity was found in the EEG of schizophrenia compared with controls. We interpreted it as the result of the psychopath's dysfunction overall brain. The surrogating procedure results in a significant increase in D(s). CONCLUSIONS: Non-linearity of the EEG in schizophrenia was proven in our study. We think the correlation dimension with spatial embedding as a good discriminating statistic for testing such non-linearity. Moreover, schizophrenic patients' EEGs were compared with controls and a lower dimension complexity was found. The results of our study indicate the possibility of using the methods of non-linear time series analysis to identify the EEGs of schizophrenic patients.     

Abnormal EEG lateralization in boys with autism.

OBJECTIVE: Functional brain abnormalities associated with autism in 3-8-year-old boys were studied with EEG recorded under controlled experimental condition of sustained visual attention and behavioral stillness. METHODS: EEG was recorded in two independent samples of boys with autism (BWA) from Moscow (N=21) and Gothenburg (N=23) and a corresponding number of age-matched typically developing boys (TDB). EEG spectral power (SP) and SP interhemispheric asymmetry within delta, theta and alpha bands were analyzed. RESULTS: BWA comprised a non-homogeneous group in relation to theta and alpha SP. When four outliers were excluded the only between-group difference in absolute SP was a higher amount of prefrontal delta in BWA. BWA of both samples demonstrated atypical leftward broadband EEG asymmetry with a maximum effect over the mid-temporal regions. Concurrently, the normal leftward asymmetry of mu rhythm was absent in BWA. CONCLUSIONS: The abnormal broadband EEG asymmetry in autism may point to a diminished capacity of right temporal cortex to generate EEG rhythms. The concurrent lack of normal leftward asymmetry of mu rhythm suggests that abnormalities in EEG lateralization in autism may be regionally/functionally specific. SIGNIFICANCE: The data provide evidence for abnormal functional brain lateralization in autism.     

EEG sleep patterns in schizophrenic patients undergoing hemodialysis

All-night electroencephalographic (EEG) sleep studies were obtained before and during a double-blind clinical trial of hemodialysis in six schizophrenic patients with normal renal functioning. No significant changes were observed in either clinical status or sleep, except for a significant reduction in rapid eye movement (REM) density, a measure of the number of eye movements per minute of REM sleep.     

Quantitative EEG in schizophrenic patients before and during pharmacotherapy

The aim of the study was to determine the possible differences in quantitative EEG parameters of schizophrenic patients before and during therapy with neuroleptics. First EEG recordings were obtained from schizophrenic patients (n = 50) who had not been taking any medicaments during the preceding 2 months. Second EEG recordings were obtained during the administration of neuroleptic therapy. Amplitude values of particular spectral segment, i.e. delta, theta, alpha 1, alpha 2, beta 1 and beta 2 (after fast Fourier transformation) were analyzed. The F3, F4, C3, C4, T3, T4, P3, P4, O1 and O2 regions were observed. The effect of pharmacotherapy manifested as a decrease in delta and beta 2 activities. The alterations of the delta spectrum were recorded in each patient subgroup (regardless of the neuroleptic used). The changes in beta 2 activity were registered in patients on haloperidol and fluphenazine.     

Abnormal EEG responses to photic stimulation in schizophrenic patients

Numerous studies have differentiated schizophrenic patients and normal controls in electroencephalography (EEG) spectral patterns recorded at rest. We replicated the resting EEG spectral differences between these groups and observed significant differences in periodic photic stimuli on the EEG spectra. Drug-free schizophrenic male patients (n = 8, mean age = 23.9) and normal male controls (n = 11, mean age = 24.3) were studied. Eighty seconds of EEG were collected from each subject for each of four experimental conditions: one resting and three photic-driving conditions (2.38, 4.54, and 8.33 Hz). Eye movement and other movement artifacts were minimized by use of an automatic amplitude threshold filter. Although large eye movements could be excluded as confounding factors, the filter could not for certain exclude small eye movements. Subjects were instructed to keep their eyes closed throughout. A significant difference was found between the groups both at rest and following photic stimulation in EEG activity. This result was characterized by increased delta activity and decreased alpha activity in schizophrenic patients at rest. The EEG activity following the photic driving also differentiated the groups. Schizophrenic patients had decreased sensitivity to the photic stimulation in the alpha range for spectra derived from both fundamental and harmonic analysis.     

EEG asymmetry in schizophrenic patients before and during neuroleptic treatment

Lateral asymmetry of electroencephalographic (EEG) spectra was assessed in schizophrenic patients compared to normal controls. Ten predominantly unmedicated schizophrenic inpatients and nine normal controls performed monitored cognitive tasks during bilateral recording of EEG from parietal and temporal sites. Lateralization of EEG power in five frequency bands was compared between the groups; separate analyses were performed for linked ears and vertex references. A subsample of schizophrenic patients was restudied after a period of neuroleptic treatment. All significant group differences were obtained with the linked ears reference only. Pretreatment schizophrenics manifested relatively less alpha power over the right hemisphere during all conditions than controls, particularly in the parietal leads. After treatment, there was a significant shift in alpha lateralization toward the control values. These latter effects were also present in the theta frequency band to a lesser extent.     

Visual search,EEG, and psychopathology in schizophrenic patients

Summary Twenty acutely admitted schizophrenic inpatients diagnosed according to RDC and 8 normal controls were instructed to search for a randomly located target letter (Z) in ten lists of 284 distractor letters of either rounded or angular shape projected on a screen (23° × 15°). Eye movements were recorded using infrared corneal reflection-pupil centre measurement. Search performance was defined as the search time in seconds from onset of the display until localization of the target. The EEG was recorded simultaneously in schizophrenics, in whom assessment took place shortly after admission and before discharge. The psychopathological status was assessed at the same time with the Brief Psychiatric Rating Scale and the Scale for the Assessment of Negative Symptoms. Search performance was not significantly different in schizophrenics and normal controls, but was heavily affected by target/distractor similarity in both groups. Moreover, search performance in schizophrenics was not significantly affected by illness severity. However, search performance was differently related to negative and positive symptoms. Schizophrenics and normal controls differed with respect to the relationship between search performance and visuomotor microbehaviour. Additionally, two relatively time-stable eye movement patterns in schizophrenics could be distinguished, which were differently related to psychopathology, performance measures and EEG.This article was presented in part at the Symposium on Eye Movements and Psychopathology, Berlin, 23–24 June 1988     

Event-related EEG field changes in aroused subjects and schizophrenic patients

The average auditory event-related potential (AAEP) to nonmeaningful stimuli has maximum vertex negative and positive amplitudes at about 100 and 200 msec, respectively. This "vertex potential" was studied under different arousal conditions in 15 normal men and 30 chronic schizophrenic subjects using the average event-related vector electro-encephalogram (AEVE) and the AAEP. The AEVE shows the path, in time, of the event-related electric field vector. To produce intramodal arousal, normal subjects also had EEG recordings made during the random sounding of a loud bell. AAEPs and AEVEs were calculated for spontaneous changes in arousal, as indicated by EEG delta band power. Bell arousal of the normal subjects increased the AAEP and AEVE measures of vertex potential maxima, thus increasing the existing differences between normals and schizophrenics. Analysis of the AEVE path indicates that arousal increased the electric field intensity, but probably did not alter, within the first 250 msec, the spatial distribution of the cortical EEG generators. After 250 msec, a reorganization of generators was indicated for the three groups. Schizophrenics differed from normals in the decreased maximum intensity of the vertex negative electric field, which was indicated by both the AEVE and AAEP.     

Left hemispheric site of EEG findings in patients with schizophrenic psychoses

It was the aim of our study to examine the interhemispherical and extrahemispherical integration that is possibly disturbed in patients suffering from schizophrenic psychoses, using an easy method of EEG performance spectral analysis. For this purpose, the EEG at rest and the functional EEG were determined in 69 schizophrenic patients (ICD) and 22 healthy subjects and the EEG reactivity was calculated. Differences especially in alpha-2 reactivity were seen both intrahemispherically and interhemispherically. This supports the concept of left hemispheric dysfunction in patients suffering from schizophrenic psychoses.     

Seizure lateralization in scalp EEG using Hjorth parameters

ObjectiveThis paper describes and assesses a new semi-automatic method for temporal lobe seizures lateralization using raw scalp EEG signals.MethodsWe used the first two Hjorth parameters to estimate quadratic mean and dominant frequency of signals. Their mean values were computed on each side of the brain and segmented taking into account the seizure onset time identified by the electroencephalographist, to keep only the initial part of the seizure, before a possible spreading to the contralateral side. The means of segmented variables were used to characterize the seizure by a point in a (frequency, amplitude) plane. Six criteria were proposed for the partitioning of this plane for lateralization.ResultsThe procedure was applied to 45 patients (85 seizures). The two best criteria yielded, for the first one, a correct lateralization for 96% of seizures and, for the other, a lateralization rate of 87% without incorrect lateralization.ConclusionsThe method produced satisfactory results, easy to interpret. The setting of procedure parameters was simple and the approach was robust to artifacts. It could constitute a help for neurophysiologists during visual inspection.SignificanceThe difference of quadratic mean and dominant frequency on each side of the brain allows lateralizing the seizure onset.     

EEG coherence in unmedicated schizophrenic patients: topographical study of predominantly never medicated cases.

Electroencephalographic (EEG) power and coherence were compared in 11 unmedicated schizophrenics (including 9 never mediated patients) and in 15 normal controls. There was no significant difference in power between the two groups. However, interhemispheric coherence between O1-O2 was higher in the schizophrenics in the delta and beta bands, and interhemispheric coherence between T5-T6 was higher in the delta band. These results suggest that coherence is more sensitive than power for comparison of these two groups, and that cerebral function is less lateralized in schizophrenics.