Effect of attention on frontal distribution of delta activity and cerebral metabolic rate in schizophrenia

Abnormal resting-state functional connectivity underlies cognitive and clinical symptoms in patients with schizophrenia

Introduction

The cognitive and psychotic symptoms in patients with schizophrenia (SZ) are thought to result from disrupted brain network connectivity.

Methods

We capitalize on the high spatiotemporal resolution of magnetoencephalography imaging (MEG) to record spontaneous neuronal activity in resting state networks in 21 SZ compared with 21 healthy controls (HC).

Results

We found that SZ showed significant global disrupted functional connectivity in delta-theta (2-8 Hz), alpha (8-12 Hz), and beta (12-30 Hz) frequencies, compared to HC. Disrupted global connectivity in alpha frequencies with bilateral frontal cortices was associated with more severe clinical psychopathology (i.e., positive psychotic symptoms). Specifically, aberrant connectivity in beta frequencies between the left primary auditory cortex and cerebellum, was linked to greater hallucination severity in SZ. Disrupted connectivity in delta-theta frequencies between the medial frontal and left inferior frontal cortex was associated with impaired cognition.

Discussion

The multivariate techniques employed in the present study highlight the importance of applying our source reconstruction techniques which leverage the high spatial localization abilities of MEG for estimating neural source activity using beamforming methods such as SAM (synthetic aperture morphometry) to reconstruct the source of brain activity, together with functional connectivity assessments, assayed with imaginary coherence metrics, to delineate how neurophysiological dysconnectivity in specific oscillatory frequencies between distinct regions underlie the cognitive and psychotic symptoms in SZ. The present findings employ powerful techniques in spatial and time-frequency domains to provide potential neural biomarkers underlying neuronal network dysconnectivity in SZ that will inform the development of innovations in future neuromodulation treatment development.

Alteration of Resting Electroencephalography by Acute Caffeine Consumption in Early Phase Psychosis

Individuals with schizophrenia use twice as much caffeine on average when compared to healthy controls. Knowing the high rates of consumption, and the potential negative effects of such, it is important we understand the cortical mechanisms that underlie caffeine use, and the consequences of caffeine use on neural circuits in this population. Using a randomized, placebo controlled, double-blind, repeated measures design, the current study examines caffeine's effects on resting electroencephalography (EEG) power in those who have been recently diagnosed with schizophrenia (SZ) compared to regular-using healthy controls (HC). Correlations between average caffeine consumption, withdrawal symptoms, drug related symptoms and clinical psychosis symptoms were measured and significant correlations with neurophysiological data were examined. Results showed caffeine had no effect on alpha asymmetry in the SZ group, although caffeine produced a more global effect on the reduction of alpha₂ power in the SZ group. Further, those with more positive symptoms were found to have a greater reduction in alpha₂ power following caffeine administration. Caffeine also reduced beta power during eyes closed and eyes open resting in HC, but only during eyes closed resting conditions in the SZ group. These findings provide a descriptive profile of the resting EEG state following caffeine administration in individuals with schizophrenia. The findings ultimately suggest caffeine does not affect alpha or beta power as readily in this population and a higher dose may be needed to achieve the desired effects, which may elucidate motivational factors for high caffeine use.

Performance prediction in a visuo-motor task: the contribution of EEG analysis

Brain state in the time preceding the task affects motor performance at single trial level. Aim of the study was to investigate, through a single trial analysis of the Power Spectral Density (PSD) of the cortical sources of EEG rhythms, whether there are EEG markers, which can predict trial-by-trial the subject's performance as measured by the reaction time (RT). 20 healthy adult volunteers performed a specific visuomotor task while continuously recorded with a 64 electrodes EEG. For each single trial, the PSD of the cortical sources of EEG rhythms was obtained from EEG data to cortical current density time series in 12 regions of interest at Brodmann areas level. Results showed a statistically significant increase of posterior and limbic alpha 1 and of frontal beta 2 power, and a reduction of frontal and limbic delta and of temporal alpha 1 power, during triggering stimulus presentation for better performance, namely faster responses. At single trial level, correlation analyses between RTs and significant PSD, revealed positive correlations in frontal delta, temporal alpha 1, and limbic delta bands, and negative ones in frontal beta 2, parietal alpha 1, and occipital alpha 1 bands. Furthermore, the subject's faster responses have been found as correlated with the similarity between the PSD values in parietal and occipital alpha 1. Predicting individual's performance at single trial level, might be extremely useful in the clinical context, since it could allow to launch rehabilitative therapies in the most efficient brain state, avoiding useless interventions.

Identifying neural signatures mediating behavioral symptoms and psychosis onset: High-dimensional whole brain functional mediation analysis

Along the pathway from behavioral symptoms to the development of psychotic disorders sits the multivariate mediating brain. The functional organization and structural topography of large-scale multivariate neural mediators among patients with brain disorders, however, are not well understood. Here, we design a high-dimensional brain-wide functional mediation framework to investigate brain regions that intermediate between baseline behavioral symptoms and future conversion to full psychosis among individuals at clinical high risk (CHR). Using resting-state functional magnetic resonance imaging (fMRI) data from 263 CHR subjects, we extract an α brain atlas and a β brain atlas: the former underlines brain areas associated with prodromal symptoms and the latter highlights brain areas associated with disease onset. In parallel, we identify and separate mediators that potentially positively and negatively mediate symptoms and psychosis, respectively, and quantify the effect of each neural mediator on disease development. Taken together, these results paint a brain-wide picture of neural markers that are potentially mediating behavioral symptoms and the development of psychotic disorders; additionally, they underscore a statistical framework that is useful to uncover large-scale intermediating variables in a regulatory biological system.

The relationship between resting electroencephalogram oscillatory abnormalities and schizotypal personality traits in the first-degree relatives of schizophrenia patients

Although a large amount of studies have manifested resting state electroencephalogram oscillatory abnormalities in schizophrenia and their first-degree relatives and in schizotype, the results are far from consistent and no research found any relationship between electroencephalograph (EEG) abnormalities and schizotypal personality in first-degree relatives. The present study is to verify the modifications of EEG power spectra in eyes-open resting state of schizophrenia and first-degree relatives, and to investigate associations between EEG band power and schizotypal personality traits in first-degree relatives of schizophrenia patients. Participant samples in this study consisted of 33 healthy normal controls, 35 unaffected first-degree relatives of schizophrenia patients and 35 schizophrenia patients. Group differences in resting EEG band power were examined via repeated-measures analysis of variance, and correlation between EEG power and schizotypal personality traits via Pearson Correlation analysis. The results showed that patients with schizophrenia exhibited increased delta, theta and alpha activity over anterior and central regions in eyes-open resting state compared with that of normal control. Gamma band power was found for the first time to be negatively correlated to schizotypal personality traits in first-degree relatives of schizophrenia patients. To conclusion, these findings suggested that low-frequency EEG activity might be neural manifestations of pathophysiological changes in the brain of schizophrenia, and gamma band activity might be an approach to measure the genetic liability of the disorder.

Reprint of: F-18Fluorodeoxyglucose positron emission tomography studies of the schizophrenia spectrum: The legacy of Monte S. Buchsbaum, M.D

This is a selective review of the work of Buchsbaum and colleagues. It revisits and pays tribute to four decades of publications employing positron emission tomography (PET) with ^F-18fluorodeoxyglucose (FDG) to examine the neurobiology of schizophrenia-spectrum disorders (including schizotypal personality disorder (SPD) and schizophrenia). Beginning with a landmark FDG-PET study in 1982 reporting hypofrontality in unmedicated schizophrenia patients, Buchsbaum and colleagues published high-impact work on regional glucose metabolic rate (GMR) abnormalities in the spectrum. Several key discoveries were made, including the delineation of schizophrenia-spectrum abnormalities in frontal and temporal lobe, cingulate, thalamus, and striatal regions using three-dimensional mapping with coregistered MRI and PET. These findings indicated that SPD patients have less marked frontal lobe and striatal dysfunction compared with schizophrenia patients, possibly mitigating frank psychosis. Additionally, these investigations were among the first to conduct early seed-based functional connectivity analyses with FDG-PET, showing aberrant cortical-subcortical circuitry and, in particular, revealing a thalamocortical circuitry abnormality in schizophrenia. Finally, pioneering work employing the first double-blind randomized antipsychotic (haloperidol) vs. placebo FDG-PET study design in schizophrenia indicated that GMR in the striatum, more than in any other region, was related to clinical response.

Frontal slow wave resting EEG power is higher in individuals at Ultra High Risk for psychosis than in healthy controls but is not associated with negative symptoms or functioning

Decreased brain activity in the frontal region, as indicated by increased slow wave EEG power measured by electrodes place on the skull over this area, in association with negative symptoms has previously been shown to distinguish ultra-high risk (UHR) individuals who later transitioned to psychosis (UHR-P) from those who did not transition (UHR-NP). The aims of the current study were to: 1) replicate these results and 2) investigate whether similar association between increased frontal slow wave activity and functioning shows any value in the prediction of transition to psychosis in UHR individuals. The brain activity, recorded using EEG, of 44 UHR individuals and 38 healthy controls was included in the analyses. Symptom severity was assessed in UHR participants and functioning was measured in both groups. The power in the theta frequency band in the frontal region of UHR individuals was higher than in controls. However, there was no difference between the UHR-P and the UHR-NP groups, and no change in slow frequency power following transition to psychosis. The correlation between delta frequency power and negative symptoms previously observed was not present in our UHR cohort, and there was no association between frontal delta or theta and functioning in either group. Increased delta power was rather correlated with depressive symptoms in the UHR group. Future research will be needed to better understand when, in the course of the illness, does the slow wave activity in the frontal area becomes impaired.

F-18Fluorodeoxyglucose positron emission tomography studies of the schizophrenia spectrum: The legacy of Monte S. Buchsbaum, M.D

This is a selective review of the work of Buchsbaum and colleagues. It revisits and pays tribute to four decades of publications employing positron emission tomography (PET) with ^F-18fluorodeoxyglucose (FDG) to examine the neurobiology of schizophrenia-spectrum disorders (including schizotypal personality disorder (SPD) and schizophrenia). Beginning with a landmark FDG-PET study in 1982 reporting hypofrontality in unmedicated schizophrenia patients, Buchsbaum and colleagues published high-impact work on regional glucose metabolic rate (GMR) abnormalities in the spectrum. Several key discoveries were made, including the delineation of schizophrenia-spectrum abnormalities in frontal and temporal lobe, cingulate, thalamus, and striatal regions using three-dimensional mapping with coregistered MRI and PET. These findings indicated that SPD patients have less marked frontal lobe and striatal dysfunction compared with schizophrenia patients, possibly mitigating frank psychosis. Additionally, these investigations were among the first to conduct early seed-based functional connectivity analyses with FDG-PET, showing aberrant cortical-subcortical circuitry and, in particular, revealing a thalamocortical circuitry abnormality in schizophrenia. Finally, pioneering work employing the first double-blind randomized antipsychotic (haloperidol) vs. placebo FDG-PET study design in schizophrenia indicated that GMR in the striatum, more than in any other region, was related to clinical response.

Sustaining attention to simple visual tasks: a central deficit in schizophrenia? A systematic review

Impairments in sustained attention, that is, the ability to achieve and maintain the focus of cognitive activity on a given stimulation source or task, have been described as central to schizophrenia. Today, sustained attention deficit is still considered as a hallmark of schizophrenia. Nevertheless, current findings on this topic are not consistent. To clarify these findings, we attempt to put these results into perspective according to the type of assessment (i.e., overall and over time assessment), the participants' characteristics (i.e., clinical and demographic characteristics), and the paradigms (i.e., traditionally formatted tasks, go/no-go tasks, and the sustained attention task) and measures used. Two types of assessment lead to opposite findings; they do not evaluate sustained attention the same way. Studies using overall assessments of sustained attention ability tend to reveal a deficit, whereas studies using over time assessments do not. Therefore, further research is needed to investigate the underlying cognitive control mechanisms of changes in sustained attention in schizophrenia.

High frequency repetitive transcranial magnetic stimulation (rTMS) reduces EEG-hypofrontality in patients with schizophrenia

The reduced metabolic activity in the prefrontal brain lobes, so-called hypofrontality, is associated with increased electrophysiological delta-band activity. Schizophrenia inpatients (N=35) received sham-controlled 10Hz rTMS over the left dorsolateral prefrontal cortex in a randomised design. After treatment, the resting electroencephalography revealed a significant decrease in the delta-band activity, which originated in the right prefrontal cortex and correlated with improvements in facial affect recognition.

[EEG frequency and regional properties in patients with paranoid schizophrenia: effects of positive and negative symptomatology prevalence]

OBJECTIVE

EEG changes in schizophrenic patients are caused by a multitude of factors related to clinical heterogeneity of the disease, current state of patients, and conducted therapy. EEG spectral analysis remains an actual methodical approach for the investigation of the neurophysiological mechanisms of the disease. The goal of the investigation was the study of frequency and regional EEG correlating with the intensity of productive and negative disorders.

MATERIAL AND METHODS

Models of summary prevalence of positive/negative disorders and evidence of concrete clinical indices of the PANSS scale were used. Spectral characteristics of background EEG in the frequency range of 1-60 Hz were studied in 35 patients with paranoid schizophrenia free from psychoactive medication and in 19 healthy volunteers.

RESULTS

It was established that the main index of negative symptomatology in summary assessment was diffuse increase of spectral power of gamma and delta ranges. Deficient states with the predominance of volitional disorders were characterized by a lateralized increase of spectral power of beta-gamma ranges in the left hemisphere, and of delta range - in frontal areas of this hemisphere. Positive symptomatology was noticeably less reflected in EEG changes than negative ones.

CONCLUSION

An analysis of psychopathological symptom complexes revealed the significance of spatially structured EEG patterns in the beta range: for the delusion disturbances with psychic automatism phenomena - in frontal areas of the left hemisphere, and for the paranoid syndrome with primary interpretative delusion - in cortical areas of the right hemisphere.

Resting state electroencephalogram oscillatory abnormalities in schizophrenia and psychotic bipolar patients and their relatives from the bipolar and schizophrenia network on intermediate phenotypes study

BACKGROUND

Abnormal resting state electroencephalogram (EEG) oscillations are reported in schizophrenia (SZ) and bipolar disorder, illnesses with overlapping symptoms and genetic risk. However, less evidence exists on whether similar EEG spectral abnormalities are present in individuals with both disorders or whether these abnormalities are present in first-degree relatives, possibly representing genetic predisposition for these disorders.

METHODS

Investigators examined 64-channel resting state EEGs of 225 SZ probands and 201 first-degree relatives (SZR), 234 psychotic bipolar (PBP) probands and 231 first-degree relatives (PBPR), and 200 healthy control subjects. Eight independent resting state EEG spectral components and associated spatial weights were derived using group independent component analysis. Analysis of covariance was conducted on spatial weights to evaluate group differences. Relative risk estimates and familiality were evaluated on abnormal spectral profiles in probands and relatives.

RESULTS

Both SZ and PBP probands exhibited increased delta, theta, and slow and fast alpha activity. Post-hoc pair-wise comparison revealed increased frontocentral slow beta activity in SZ and PBP probands as well as SZR and PBPR. Augmented frontal delta activity was exhibited by SZ probands and SZR, whereas PBP probands and PBPR showed augmented fast alpha activity.

CONCLUSIONS

Both SZ and PBP probands demonstrated aberrant low-frequency activity. Slow beta activity was abnormal in SZ and PBP probands as well as SZR and PBPR perhaps indicating a common endophenotype for both disorders. Delta and fast alpha activity were unique endophenotypes for SZ and PBP probands, respectively. The EEG spectral activity exhibited moderate relative risk and heritability estimates, serving as intermediate phenotypes in future genetic studies for examining biological mechanisms underlying the pathogenesis of the two disorders.

Frontal delta power associated with negative symptoms in ultra-high risk individuals who transitioned to psychosis

It has recently been shown that treatment with long-chain omega-3 polyunsaturated fatty acids (PUFAs) could decrease the rate of transition to psychosis, and improve psychiatric symptoms and global functioning in people at ultra-high risk (UHR) for psychosis. Previous studies have suggested that resting state brain activity measured with electroencephalography (EEG) may represent an objective biomarker of changes in neural function associated with supplementation with omega-3 PUFAs. It has also been proposed that although resting state EEG cannot, by itself, predict transition to psychosis in UHR individuals, the combination of resting state EEG with negative symptoms may be a valid predictor of transition. The present study investigated whether treatment with omega-3 PUFAs influenced resting state EEG in UHR participants, and whether or not the association of the participants' resting state EEG with their levels of negative symptoms was dependent on their transition status. The brain activity of 73 UHR participants was recorded in the context of a randomized, placebo-controlled trial of the effects of supplementation with omega-3 PUFAs. The UHR participants who subsequently transitioned to psychosis (UHR+) did not differ from those who did not transition (UHR-) in terms of resting state EEG power in any frequency band. However, negative symptom scores were associated with increased delta activity in the frontal region of the UHR+ participants, but not in the UHR- participants. Treatment with omega-3 PUFAs did not induce changes in resting state EEG in either group. The results suggest that decreased frontal delta activity, in combination with high levels of negative symptoms, may be a risk factor for subsequent transition to psychosis in UHR individuals.

Decreased α event-related synchronization in the left posterior temporal cortex in schizophrenia: a magnetoencephalography-beamformer study

Alpha rhythm is one of the most prominent electromagnetic changes in the brain, and electroencephalography (EEG) alpha reactivity disturbance may sometimes represent an early sign of cerebral dysfunction. Although magnetoencephalography (MEG) has a better spatial resolution than EEG, it has not extensively been used to explore alpha-power change deficits in schizophrenia as a possible neurophysiological marker of the disease. The purpose of this study was to use MEG to identify abnormalities in alpha synchronization induced by eye-closing in schizophrenia patients compared to healthy controls, and to investigate whether alpha reactivity deficits correlate with clinical features of the disorder. MEG data were recorded in 22 schizophrenia patients and 20 age- and gender-matched controls during eyes-open/eyes-closed resting states. Cortical sources of event-related synchronization (ERS) were estimated using multiple source beamformer, and BrainVoyager was used for statistic group analysis. A significant decrease in ERS in the upper alpha band (10-13 Hz) was found in the left posterior temporal region in schizophrenia patients relative to controls, and this activity showed correlation with visual memory scores. This upper alpha ERS deficit may indicate left temporal dysfunction and visual-information processing impairment in schizophrenia, and upon further confirmation it might represent a neurophysiological state marker of the disorder.

Delta EEG band as a marker of left hypofrontality for language in schizophrenia patients

Frontal hypoactivation has consistently been demonstrated in schizophrenia patients. We hypothesized that this well-known deficit is asymmetrical, ie, centered over left frontal locations and, in-line with Crow's theory, associated with both loss of linguistic asymmetry and correlated with positive symptoms. Electroencephalography delta band was used as a quantitative index of cortical inhibition in 17 paranoid schizophrenia patients with prevailing positive symptoms and 17 matched control subjects. Delta amplitude was measured by 38 electrodes, while participants performed 3 linguistic tasks, visuoperceptual, rhyming, and semantic judgment. Compared with control subjects, patients did not show overall delta band differences, revealing no detrimental effects of pharmacological treatment. In healthy participants, analysis of 4 quadrants/regions of interest revealed higher delta amplitude in right vs left anterior sites, indicating significant left anterior disinhibition during linguistic processing. Instead, patients showed bilateral delta band distribution and, compared with control subjects, significant greater delta amplitude (ie, brain inhibition) in linguistic left anterior centers. Patients' left hypofrontality was functionally related to their lack of hemispheric specialization for language and was positively correlated with higher levels of delusions (P1) and conceptual disorganization (P2) Positive and Negative Syndrome Scale subscales. Results suggest, in schizophrenia patients, a functional deficit of Broca's area, a region playing a fundamental hierarchical role between and within hemispheres by integrating many basic processes in linguistic and conceptual organization. The significant correlation between lack of anterior asymmetry and increased positive symptoms is in-line with Crow's hypothesis postulating the etiological role of disrupted linguistic frontal asymmetry on the onset of the key symptoms of schizophrenia.

LORETA analysis of three-dimensional distribution of δ band activity in schizophrenia: relation to negative symptoms

We sought to determine if altered electroencephalography (EEG) activities, such as delta band activity, in specific brain regions are associated with psychotic symptoms. Data were obtained from 17 neuroleptic-naive patients with schizophrenia and age- and sex-matched 17 healthy control subjects. Low Resolution Brain Electromagnetic Tomography (LORETA) was used to generate current source density images of delta, theta, alpha, and beta activities. Localization of the difference in EEG activity between the two groups was assessed by voxel-by-voxel non-paired t-test of the LORETA images. Spearman's correlation coefficient was obtained to relate LORETA values of EEG current density in brain regions showing a significant between-group difference and psychopathology scores. Delta band activity, represented by LORETA current density, was greater for patients in the following areas; the left inferior temporal gyrus, right middle frontal gyrus, right superior frontal gyrus, right inferior frontal gyrus, and right parahippocampal gyrus. LORETA values for delta band activity in the above five brain regions were negatively correlated with negative, but not positive symptoms. The results of this study suggest the role for electrophysiological changes in some of the brain regions, e.g. prefrontal cortex, in the manifestation of negative symptoms.

Alpha rhythm and hypofrontality in schizophrenia

OBJECTIVE

To reveal the EEG correlates of resting hypofrontality in schizophrenia (SZ).

METHOD

We analyzed the whole-head EEG topography in 14 patients compared to 14 matched controls by applying a new parameterization of the multichannel EEG. We used a combination of power measures tuned for regional surface mapping with power measures that allow evaluation of global effects.

RESULTS

The SZ-related EEG abnormalities include i) a global decrease in absolute EEG power robustly manifested in the alpha and beta frequency bands, and ii) a relative increase in the alpha power over the prefrontal brain regions against its reduction over the posterior regions. In the alpha band both effects are linked to the SZ symptoms measured with Positive and Negative Symptom Scales and to chronicity.

CONCLUSION

As alpha activity is related to regional deactivation, our findings support the concept of hypofrontality in SZ and expose the alpha rhythm as a sensitive indicator of it.

Sleep deprivation PET correlations of Hamilton symptom improvement ratings with changes in relative glucose metabolism in patients with depression

BACKGROUND

This PET study is a continuing investigation of the effects of antidepressant medication and one night of total sleep deprivation on cerebral metabolism in depressed patients. This study was undertaken to confirm previous correlations between symptom improvement ratings and regional changes in glucose metabolism, using a higher resolution scanner than in previous investigations. In addition, we also studied the effect of concomitant antidepressant medication in conjunction with sleep depression.

METHOD

Six depressed patients were administered the selective serotonin reuptake inhibitor sertraline for a week and then underwent positron emission tomography (FDG PET) before and after sleep deprivation. Changes in relative glucose metabolism were correlated with symptom improvement ratings in Hamilton Depression Rating Scale scores.

RESULTS

Positive correlations (defined as reduced HDRS scores associated with areas having reduced relative cerebral glucose metabolism after TSD) were found in the inferior frontal gyrus and inferior frontal/orbital frontal cortex. Negative correlations (defined as reduced HDRS scores associated with areas of increased relative cerebral glucose metabolism after TSD) were found in the dorsolateral prefrontal cortex.

LIMITATIONS

Limitations of this study are that the number of subjects was small (n=6) and they were scanned at a 7.6 mm resolution.

CONCLUSIONS

The results of this study support previous findings on the effects of sleep deprivation and antidepressant medications in the treatment of unipolar and bipolar depression, with an emphasis on the significance of cerebral glucose metabolic changes in the ventral and DLPF cortex in mood regulation.

Effect of low-frequency rTMS on electromagnetic tomography (LORETA) and regional brain metabolism (PET) in schizophrenia patients with auditory hallucinations

BACKGROUND

Auditory hallucinations are characteristic symptoms of schizophrenia with high clinical importance. It was repeatedly reported that low frequency (<or=1 Hz) repetitive transcranial magnetic stimulation (rTMS) diminishes treatment-resistant auditory hallucinations. A neuroimaging study elucidating the effect of rTMS in auditory hallucinations has yet to be published.

OBJECTIVE

To evaluate the distribution of neuronal electrical activity and the brain metabolism changes after low-frequency rTMS in patients with auditory hallucinations.

METHODS

Low-frequency rTMS (0.9 Hz, 100% of motor threshold, 20 min) applied to the left temporoparietal cortex was used for 10 days in the treatment of medication-resistant auditory hallucinations in schizophrenia (n = 12). The effect of rTMS on the low-resolution brain electromagnetic tomography (LORETA) and brain metabolism ((18)FDG PET) was measured before and after 2 weeks of treatment.

RESULTS

We found a significant improvement in the total and positive symptoms (PANSS), and on the hallucination scales (HCS, AHRS). The rTMS decreased the brain metabolism in the left superior temporal gyrus and in interconnected regions, and effected increases in the contralateral cortex and in the frontal lobes. We detected a decrease in current densities (LORETA) for the beta-1 and beta-3 bands in the left temporal lobe whereas an increase was found for beta-2 band contralaterally.

CONCLUSION

Our findings implicate that the effect is connected with decreased metabolism in the cortex underlying the rTMS site, while facilitation of metabolism is propagated by transcallosal and intrahemispheric connections. The LORETA indicates that the neuroplastic changes affect the functional laterality and provide the substrate for a metabolic effect.

Comparison of simultaneously recorded [H2(15)O]-PET and LORETA during cognitive and pharmacological activation

The complementary strengths and weaknesses of established functional brain imaging methods (high spatial, low temporal resolution) and EEG-based techniques (low spatial, high temporal resolution) make their combined use a promising avenue for studying brain processes at a more fine-grained level. However, this strategy requires a better understanding of the relationship between hemodynamic/metabolic and neuroelectric measures of brain activity. We investigated possible correspondences between cerebral blood flow (CBF) as measured by [H2O]-PET and intracerebral electric activity computed by Low Resolution Brain Electromagnetic Tomography (LORETA) from scalp-recorded multichannel EEG in healthy human subjects during cognitive and pharmacological stimulation. The two imaging modalities were compared by descriptive, correlational, and variance analyses, the latter carried out using statistical parametric mapping (SPM99). Descriptive visual comparison showed a partial overlap between the sets of active brain regions detected by the two modalities. A number of exclusively positive correlations of neuroelectric activity with regional CBF were found across the whole EEG frequency range, including slow wave activity, the latter finding being in contrast to most previous studies conducted in patients. Analysis of variance revealed an extensive lack of statistically significant correspondences between brain activity changes as measured by PET vs. EEG-LORETA. In general, correspondences, to the extent they were found, were dependent on experimental condition, brain region, and EEG frequency.

Relationship between power spectra of the awake EEG and psychomotor activity patterns measured by short-term actigraphy

Actigraphy is a quantitative method for the measurement of motor activity. In the present study, actigraphy was used to examine psychomotor correlates of brain activity. Thirty-four psychiatric patients (17 males and 17 females) with different diagnoses participated in this investigation. Directly after EEG recording, motor activity was measured with a wrist actimeter for 15 min in patients in the sitting position. The EEG was quantified by spectrum analysis, and the power spectra as well as other EEG-derived variables were correlated with actigraphic parameters. Occipital and temporoparietal beta1 power was statistically significantly higher in patients with higher activity scores and lower in those with a high density of sleep (SB) or wake bouts (WB). A high density of SB or WB was also positively correlated with higher mean alpha power. Immobile phases measured by actigraphy were positively associated with occipital alpha and with frontal/frontopolar delta activity, preferentially on the side of the left hemisphere. Our results, while preliminary, suggest that short-term actigraphy may be apt to reflect central nervous system arousal.

Neurocortical electrical activity tomography in chronic schizophrenics

Functional imaging of brain electrical activity was performed in 25 chronic medicated schizophrenics and 40 controls, analyzing the classical frequency bands (delta, theta, alpha, and beta) of 19-channel EEG during resting state to identify brain regions with deviant activity of different functional significances, using LORETA (Low Resolution Tomography) and SPM99 (Statistical Parametric Mapping). Patients differed from controls due to an excess of slow activity comprising delta + theta frequency bands (inhibitory pattern) located at the right middle frontal gyrus, right inferior frontal gyrus, and right insula, as well as at the bilateral anterior cingulum with a left preponderance. The high temporal resolution of EEG enables the specification of the deviations not only as an excess or a deficit of brain electrical activity, but also as inhibitory (delta, theta), normal (alpha), and excitatory (beta) activities. These deviations point out to an impaired functional brain state consisting of inhibited frontal and prefrontal areas that may result in inadequate treatment of externally or internally generated information.

Cortical hypoactivation during resting EEG in schizophrenics but not in depressives and schizotypal subjects as revealed by low resolution electromagnetic tomography (LORETA)

This study was performed in order to address the question whether the newly introduced technique of low-resolution electromagnetic tomography (LORETA) is able to detect hypofrontality in schizophrenic patients. We investigated resting EEGs of 19 unmedicated schizophrenics and 20 normal subjects. For comparison, we also investigated 19 subjects with schizotypal personality and 30 unmedicated depressive patients. A significant increase of delta activity was found in schizophrenic patients over the whole cortex, most strongly in the anterior cingulate gyrus and temporal lobe (fusiform gyrus). Both schizotypal subjects and depressive subjects showed significantly less delta, theta and beta activity in the anterior cingulum, a decrease of alpha1 activity in the right temporal lobe and a decrease of alpha2 activity in the left temporal lobe. The results suggest general cortical hypoactivation, most pronounced in the anterior cingulate and temporal lobe in schizophrenics, whereas there is evidence for a complex, frequency-dependent spatial pattern of hyperactivation in schizotypal subjects and depressive patients. The results are discussed within a neurophysiological and methodological framework.

Eeg alpha rhythm and glucose metabolic rate in the thalamus in schizophrenia

Positron emission tomography with uptake of [(18)F]fluorodeoxyglucose (FDG) and quantitative EEG were simultaneously performed in 18 medication-free patients with schizophrenia and in 13 normal volunteers. Subjects performed the Continuous Performance Task (CPT) during FDG uptake. Correlations were calculated between alpha power during the CPT and glucose metabolic rate (GMR) in thalamic regions and between alpha power during the CPT and GMR in occipital cortices. Regression analyses were used to describe the prediction of GMR in the occipital cortices and in the thalamic regions of occipital alpha power. In normal controls, we found (1) significant negative correlations between absolute alpha power and GMR in the left occipital cortex, (2) significant positive correlations between normalized alpha power and GMR in the right and left lateral thalamus and (3) combined effects of GMR in the thalamic regions and the occipital cortices on alpha power, which accounted for 98% of the variance of alpha power. In patients with schizophrenia, we found no significant correlations between alpha power and GMR in the occipital cortices or between alpha power and GMR in the thalamic regions. Correlation coefficients between absolute alpha power and GMR in the left occipital cortex and between normalized alpha power and GMR in the left lateral thalamus were significantly different in normal subjects compared to schizophrenic patients. The present findings provide evidence for involvement of the thalamus in the generation of alpha rhythm in humans. Furthermore, the present results suggest differences in thalamocortical circuits between normal controls and schizophrenic subjects.

Continuous performance tests are sensitive to ADHD in adults but lack specificity. A review and critique for differential diagnosis

Historically, the focus for Attention Deficit Hyperactivity Disorder (ADHD) has been on children, with considerable research and many opinions available in this area. More recently, the focus has been expanded to include ADHD in adults. Assessment of ADHD in adults is complicated by the high rate of co-occurring disorders as well as symptom overlap with a number of disorders. One popular family of measures for the assessment of attention and executive control is the continuous performance test (CPT). A review of the available research on CPTs reveals that they are quite sensitive to CNS dysfunction. This is both a strength and a limitation of CPTs in that multiple disorders can result in impaired performance on a CPT. The high sensitivity of CPTs is further complicated by the multiple variations of CPTs available, some of which may be more sensitive or demonstrate better specificity to ADHD in adults than others. If CPTs are to be used clinically, further research will be needed to answer the questions raised by this review.

An association between reduced interhemispheric EEG coherence in the temporal lobe and genetic risk for schizophrenia

Previous studies have suggested that schizophrenic patients show resting changes such as frequency-slowing and decreased coherence in the frontal and temporal area. We sought to determine whether these findings are also found in clinically unaffected siblings of schizophrenics and estimate heritability by calculating relative risk. We investigated two independent data sets: (1) from the NIMH St. Elisabeth's campus (59 schizophrenics, 76 unaffected siblings and 32 unrelated normal controls) and (2) from the NIH-campus (Bethesda) (59 schizophrenics, 90 unaffected siblings and 26 unrelated normal controls). We computed power spectra and coherence on the first data set and then tried to replicate the results on the second data set. Power spectrum analysis suggested that schizophrenics are cortically hypoactivated, whereas in unaffected siblings, a tendency for hyperactivation was found. In contrast, spectral coherences (0.5-5Hz) were reduced in both data sets in the temporal lobe areas in schizophrenics and in their unaffected siblings. Changes were most pronounced for the interhemispheric coherence linking both posterior temporal lobe areas. Relative risk calculations (lambda(S)) ranged between 3.7 and 9.8, depending on phenotype definition. Thus, while power spectrum EEG abnormalities may be state-dependent, reduced coherence as a possible measure of neuronal synchronization is familial and potentially a heritable trait related to genetic risk for schizophrenia.

Hypofrontality -- a risk-marker related to schizophrenia?

In order to better understand whether cortical hypoactivation and hypofrontality is a possible risk marker for schizophrenia, we investigated resting EEG activity in 39 unmedicated schizophrenics and 21 persons with schizotypal personality. Compared to a normal control group, we found an increased, frontally pronounced delta activity in schizophrenic patients, a result that is in accordance with other studies. Subjects with schizotypal personality, who are believed to have an increased risk for schizophrenia, did not show an increase of delta activity. From this result, we concluded that cortical hypoactivation and hypofrontality -- defined as an increase of frontally pronounced delta activity during resting EEG -- cannot be interpreted as a risk factor for schizophrenia. However, since it is controversial whether subjects with schizotypal personality are at increased risk for schizophrenia, further studies in unaffected family members of schizophrenic patients are needed.

Clinical and biological concomitants of resting state EEG power abnormalities in schizophrenia

BACKGROUND

This study investigated the clinical and biological concomitants of electroencephalogram power abnormalities in schizophrenia.

METHODS

We examined the power characteristics of resting electroencephalograms in 112 schizophrenic patients. Also collected were measures of psychotic symptomatology, brain morphology, ocular motor functioning, electrodermal activity, and nailfold plexus visibility. Seventy-eight nonschizophrenic psychosis patients (e.g., mood disorder patients with psychosis) and 107 nonpsychiatric control subjects were included for comparison.

RESULTS

Schizophrenic patients whose electroencephalograms were characterized by augmented low-frequency power and diminished alpha-band power had more negative symptoms, larger third ventricles, larger frontal horns of the lateral ventricles, increased cortical sulci widths, and greater ocular motor dysfunction compared with schizophrenic patients without these electroencephalogram characteristics. In nonschizophrenic psychosis patients, augmented low-frequency and diminished alpha-band powers failed to be associated with any clinical or biological indices.

CONCLUSIONS

Results suggest that clinical and biological concomitants of low-frequency and alpha-band power abnormalities in schizophrenia are unique, perhaps indicating the presence of thalamic and frontal lobe dysfunction.

Correlation of qEEG with PET in schizophrenia

PET relative metabolism was correlated with quantitative EEG in 9 schizophrenic patients. The PET metabolic regions of interest were the frontal lobes, thalamus and basal ganglia, and right and left temporal lobes. Significant positive correlations were seen for the frontal lobes and delta EEG power, and alpha power with subcortical metabolism. The physiologic plausibility of those correlations is discussed with reference to the possible effect of neuroleptic medication.

Low resolution brain electromagnetic tomography (LORETA) functional imaging in acute, neuroleptic-naive, first-episode, productive schizophrenia

Functional imaging of brain electrical activity was performed in nine acute, neuroleptic-naive, first-episode, productive patients with schizophrenia and 36 control subjects. Low-resolution electromagnetic tomography (LORETA, three-dimensional images of cortical current density) was computed from 19-channel electroencephalographic (EEG) activity obtained under resting conditions, separately for the different EEG frequencies. Three patterns of activity were evident in the patients: (1) an anterior, near-bilateral excess of delta frequency activity; (2) an anterior-inferior deficit of theta frequency activity coupled with an anterior-inferior left-sided deficit of alpha-1 and alpha-2 frequency activity; and (3) a posterior-superior right-sided excess of beta-1, beta-2 and beta-3 frequency activity. Patients showed deviations from normal brain activity as evidenced by LORETA along an anterior-left-to-posterior-right spatial axis. The high temporal resolution of EEG makes it possible to specify the deviations not only as excess or deficit, but also as inhibitory, normal and excitatory. The patients showed a dis-coordinated brain functional state consisting of inhibited prefrontal/frontal areas and simultaneously overexcited right parietal areas, while left anterior, left temporal and left central areas lacked normal routine activity. Since all information processing is brain-state dependent, this dis-coordinated state must result in inadequate treatment of (externally or internally generated) information.

Electroencephalographic findings in functional psychoses: state or trait indicators?

The clinical significance of electroencephalographic (EEG) changes in patients with functional psychoses is not yet clearly defined, particularly whether these changes are state indicators or trait indicators. In the present review, the EEG abnormalities in schizophrenia are discussed. In early EEG studies of schizophrenics, the various specific EEG patterns were suggested to be trait indicators, but those findings were not confirmed. The EEG patterns of some patients with catatonic schizophrenia, especially periodic catatonia, were thought to be episode or state indicators, and some of the patients diagnosed as having atypical psychoses in Japan were suggested to show state indicator EEG findings. As the computerized and spectral analyses of EEG have advanced, the contradictory findings of EEG in schizophrenia have been reported, interpreted as 'hyperstable' or 'hypernormal' EEG findings and 'hypofrontal' EEG findings (slow waves in the frontal region). However, no conclusion can be made as to whether these EEG findings are state or trait indicators. On the borderland of functional psychoses, the behavioral changes in temporal lobe epilepsy were described as a trait indicator, and the psychotic states in non-convulsive generalized status epilepticus and acute confusional states were suggested to be state indicators. Further studies of EEG abnormalities in schizophrenia are necessary from multi-dimensional perspectives, including in comparison with the symptomatic psychoses.

Chemical and physiologic brain imaging in schizophrenia

Technologic advances in functional brain imaging have provided exciting and informative insights into the functional neuroanatomy and neurochemistry of schizophrenia. Using MR spectroscopy, it has been possible to examine in vivo brain metabolism and to relate observed changes to physiological processes occurring at a cellular level. Positron emission tomography and single photon emission computed tomography have revealed disturbances of cerebral blood flow and glucose metabolism in patients with schizophrenia. More recently, these tools have also proved most useful in studying the relative receptor occupancy of typical and atypical antipsychotic medications.

A robust assessment of the NoGo-anteriorisation of P300 microstates in a cued Continuous Performance Test

The Continuous Performance Test (CPT) is successfully applied in clinical routine to evaluate attentional performance. The aim of the present study was to investigate the features of the ERPs related to the conditions of a cued CPT, in particular the Go- and the NoGo-condition demanding either the execution or the inhibition of a prepared motor response. For that purpose, 21-channel-ERPs of ten healthy subjects elicited by the Go, NoGo, primer and distractor cues were analyzed with reference-independent methods. The P300 microstates were identified by means of a data-driven segmentation of the ERPs based on the individual peaks of the Global Field Power (GFP). The topographical assessment of the P300 fields yielded an extraordinarily robust result consisting of a more anterior location of the positive centroid in the NoGo compared to the Go condition in every single subject. In conclusion, this result is an impressive validation of the applied reference-independent spatial analysis which reveals the rapid changes of the brain electrical field configurations related to the execution/inhibition paradigm within the cued CPT. Because of the stability of the NoGo anteriorisation we propose to use this parameter as a topographical standard index, analogous to the amplitude effect between oddball targets and nontargets which defines the classical P300.

Cortical localization of human sustained attention: detection with functional MR using a visual vigilance paradigm

PURPOSE

Our goal was to determine whether functional MRI on a standard 1.5 T system can localize activation during a visual vigilance sustained attention task and whether this corresponds to results described in a PET investigation of a similar task.

METHOD

Sixteen volunteers were studied on a 1.5 T system using a gradient echo technique. A single axial section was oriented within a stereotaxic coordinate space, 40 mm superior to the anterior-posterior commissure line. Images with eyes closed were followed by images during subject concentration on a small dim spot. Motion correction and pixel-by-pixel statistical analysis were performed. Talairach grids were applied for summary statistical analysis and comparison to PET data, with analysis using a series of planned contrasts within a repeated measures analysis of variance.

RESULTS

Predominantly right-sided frontal and parietal activation was observed, with statistical significance across subjects in the right frontal lobe (F > or = 5.9, p < or = 0.041). Comparison with previously reported PET data yielded a very similar pattern of activation (F = 13.2; df = 1,8; p = 0.007).

CONCLUSION

Activation of the right middle frontal gyrus and right parietal lobe during visual vigilance is detectable across functional imaging modalities.

Cerebral metabolic change after treatment in biotinidase deficiency

A 13.5-year-old boy with biotinidase deficiency was studied 8 days before and 5 months after biotin treatment by positron emission tomography (PET) and computerized electroencephalographic topography (CET). With biotin treatment there was a marked improvement in the presenting symptom of loss of visual acuity and a more modest recovery in spastic quadraparesis. By PET scanning, the relative metabolic rate for glucose was more than 2 standard deviations lower in the temporal and occipital cortices than in adult or age-matched controls. With biotin treatment, these values rose to normal limits for both control groups. By CET, normalized EEG equivalent to the relative glucose metabolic rate showed asymmetric slowing in the left temporal and frontal regions before treatment, whereas none of the 32 leads exceeded normal limits of delta, theta, alpha or beta after treatment. These results suggest a strong correlation between clinical, metabolic and electrical measures of brain function as related to biotin treatment in biotinidase deficiency.

Computerized EEG topography findings in schizophrenic patients before and after haloperidol treatment

An increase of delta and fast beta activity in schizophrenic patients when compared with normal controls has been consistently reported. Topography of these abnormalities, in particular a possible frontal localization of delta, and their relationship to drug treatment and clinical status are still debated. In order to assess these issues, a multilead CEEG investigation was carried out in a group of 20 DSM-III-R schizophrenics, both before and after haloperidol treatment. All findings are described in terms of amplitude and relative power. Drug-free schizophrenics, when compared with a group of normal controls, showed a generalized increase of delta and fast beta, and a decrease of alpha 2 relative power. After acute treatment, patients showed a significant decrease of delta, and an increase of theta 2, beta 1, and beta 2. After 28 days of haloperidol treatment, similar changes were observed for delta, together with an increase of alpha 1, and a decrease of fast beta.

Adolescent developmental change in topography of EEG amplitude

EEGs were recorded from 32 channels in 30 normal males, ages 16-22. Delta activity decreased throughout this age range. This decrease was greatest in the left frontal and temporal regions; no occipital lead showed this pattern. Relative EEG amplitude analysis, based on normalized maps, revealed decreases with age across alpha, delta, and theta bands with beta staying the same or increasing. These changes were greatest in the left temporal and left frontal regions. Taken together, these findings suggest that these cortical areas are maturing in the second decade of life. Both delta and theta showed significantly greater decreases with age in the left parietal region than in the right.

MRI-SPECT and PET-EEG findings on brain dysfunction in schizophrenia

1. In this article the author reviews a series of investigations on brain dysfunction in untreated schizophrenics using manumotor and music listening tasks as activation paradigms. Methods involved were EEG mapping, Single Photon Emission Computerized Tomography (SPECT; Xenon-133 inhalation method), Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET; 11-2-Deoxyglucose as tracer). 2. Major signs of brain dysfunction yielded a "nonreactivity" on both motor and music stimulation in patients displaying marked negative symptomatology, as shown consistently by EEG Mapping, SPECT and PET. In contrast, first-break patients with predominant "positive" and without underlying negative symptoms showed signs of "normal" to "diffuse hyperactivation" on such stimulations, as demonstrated by EEG and SPECT imaging methods. 3. Interestingly, MRI planimetry of the size of the corpus callosum (CC) corroborated the above findings, showing a significantly larger CC in "positive" than "negative" patients. 4. Together with functional imaging findings of other working groups and recent neuropathological theories we finally raise some speculative neurophysiological hypotheses on brain dysfunction in subgroups of schizophrenics, which might have direct implications for treatment and follow-up of these patients.

Hypofrontality on topographic EEG in schizophrenia. Correlations with neuropsychological and psychopathological parameters

Topographic EEG was performed in 17 DSM-III-R schizophrenic patients and in 15 sex- and age-matched healthy controls. Eleven patients were first-onset (neuroleptic naive) schizophrenics. EEG band power was compared with psychopathology, neuropsychology and neurological soft signs. The EEG was recorded at 14 topographic locations monopolarly and movements of the eye and of the lid were monitored by two bipolar electro-oculogram (EOG) derivations, one vertical and one horizontal. A multivariate correction of EOG artefacts was performed based on regression analysis with respect to EOG channels. Schizophrenic patients showed higher mean and median power in most bands. These differences were marked in the delta band, in the fast alpha and beta bands, in particular at left frontal sites. Delta power at F7 was by far the best separating variable between schizophrenics and controls in a discriminant analysis. Significant positive correlations were found between the Brief Psychiatric Rating Scale scores "Anxiety-depression" and "Activation" and power in the fast bands and negative ones between "Anergia" and the beta bands. Positive significant correlations emerged between the total score in the Negative Symptoms Rating Scale and the amount of delta power, predominantly over the temporal region. Impairment in the Luria-Nebraska neuropsychological scores "Rhythm" and "Memory" correlated highly significantly with EEG band power. No correlations were found between neurological soft signs and EEG band power. Our results are in line with the hypothesis of a hypofrontality in schizophrenia. It is unlikely that these findings are an artefact of prior psychiatric treatment, as they were also observed in first-onset, neuroleptic naive schizophrenics.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain dysfunction during motor activation and corpus callosum alterations in schizophrenia measured by cerebral blood flow and magnetic resonance imaging

Sixteen unmedicated (14 never-medicated, 2 with washout periods of 1-2 weeks) schizophrenic patients displaying positive symptoms (e.g., formal thought disorder, hallucinations, delusions) without negative symptoms (e.g., flattening of affect, loss of energy, anhedonia--type I patients), 15 unmedicated (with washout periods from 1 week to 2 years) patients with marked negative symptomatology [type II patients; criterion score below 15/above 35 on the Munich version of the Scale of Assessment of Negative Symptoms (SANS), respectively], and 31 matched normal controls were investigated using regional cerebral blood flow [rCBF; dynamic single-photon emission computerized tomography (SPECT) with Xenon-133 as tracer] and magnetic resonance imaging (MRI; spin-echo technique, T1 weighted, midsagittal cuts). rCBF measurements were performed during both resting conditions and simple motor activation. Separately, on the same day, we performed a planimetric evaluation of the callosal-brain ratio in all subjects using MRI. In accordance with previous results on a smaller sample, we found signs of diffuse bilateral rCBF hyperactivation in type I patients, as compared with signs of nonreactivity in type II schizophrenics. Both activation patterns were different from a strictly contralateral sensorimotor rCBF activation seen in normal persons (only 8 studied with SPECT). The planimetry of relative callosal area did not reveal differences compared to normal persons, when type I/II patients were taken together. However, the threefold increased variance as compared with that found in normal persons suggested biological heterogeneity in patients. We found an increase of relative callosal size in type I as compared with type II patients. In the light of some recent findings linking lack of laterality of several brain functions to increased callosal size, we propose lack of laterality/diffuse hyperactivation and increased callosal size to be connected with positive symptomatology/good prognosis schizophrenia, and vice versa.