Size matters: Grey matter brain reserve predicts executive functioning in the elderly

Preserved executive functioning (EF) is crucial for daily functioning in the elderly and it appears to predict dementia development. We sought to clarify the role of atrophy-corrected cortical grey matter (GM) volume as a potential brain reserve (BR) marker for EF in the elderly. In total, 206 pre-surgical subjects (72.50 ± 4.95 years; mean MMSE score 28.50) were investigated. EF was primarily assessed using the Trail Making Test B (TMT B). Global/ lobar GM volumes were acquired with T1 MP-RAGE. Adjusting for key covariates including a brain atrophy index (i.e. brain parenchymal fraction), multiple linear regression analysis was used to study associations of GM volumes and TMT B. All GM volumes - most notably of global GM - were significantly associated with TMT B independently of GM atrophy (ß = -0.201 to -0.275, p = 0.001-0.012). Using atrophy-corrected GM volume as an estimate of maximal GM size in youth may serve as a BR predictor for cognitive decline in future studies investigating BR in the elderly.

Diabetes is associated with risk of postoperative cognitive dysfunction: A meta-analysis

BACKGROUND

Postoperative cognitive dysfunction (POCD) occurs frequently after surgery, particularly among older people. Diabetes, chronic hyperglycemia, and a history of hypoglycemia are related to cognitive impairment, but little is known about their roles in POCD. Here, we estimated their associations with risk of POCD on the basis of published epidemiological research.

METHODS

The PubMed and Cochrane databases were searched for longitudinal studies of adults undergoing surgery with reporting of associations of diabetes status, glycemic levels, and/or a history of hypoglycemia with risk of POCD as relative risks or odds ratios. Meta-analysis Of Observational Studies in Epidemiology (MOOSE) and Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were followed.

RESULTS

The search identified 246 publications of which 14 met inclusion criteria, reporting on a total of 2642 patients (mean age 64 y). Follow-up periods spanned 1 day to 5 years. Overall, patients with diabetes had a 1.26-fold higher risk of POCD compared with diabetes-free patients (95% CI, 1.12-1.42). A single study assessed glycemic control in patients with diabetes and identified a higher hemoglobin A1c (HbA1c) level as associated with higher POCD risk (relative risk per percent higher HbA1c, 2.0; 95% CI, 1.4-2.6). We did not find studies on glycemic levels in the nondiabetic range or on hypoglycemia as potential predictors of POCD.

CONCLUSION

Patients with diabetes appear to have a higher risk of POCD compared with diabetes-free persons. Among patients with diabetes, POCD risk may further increase with poorer glycemic control as indexed by higher HbA1c. The roles of HbA1c levels among nondiabetic persons in POCD risk warrant further research.

Structural brain changes are associated with response of negative symptoms to prefrontal repetitive transcranial magnetic stimulation in patients with schizophrenia

Impaired neural plasticity may be a core pathophysiological process underlying the symptomatology of schizophrenia. Plasticity-enhancing interventions, including repetitive transcranial magnetic stimulation (rTMS), may improve difficult-to-treat symptoms; however, efficacy in large clinical trials appears limited. The high variability of rTMS-related treatment response may be related to a comparably large variation in the ability to generate plastic neural changes. The aim of the present study was to determine whether negative symptom improvement in schizophrenia patients receiving rTMS to the left dorsolateral prefrontal cortex (DLPFC) was related to rTMS-related brain volume changes. A total of 73 schizophrenia patients with predominant negative symptoms were randomized to an active (n=34) or sham (n=39) 10-Hz rTMS intervention applied 5 days per week for 3 weeks to the left DLPFC. Local brain volume changes measured by deformation-based morphometry were correlated with changes in negative symptom severity using a repeated-measures analysis of covariance design. Volume gains in the left hippocampal, parahippocampal and precuneal cortices predicted negative symptom improvement in the active rTMS group (all r⩽-0.441, all P⩽0.009), but not the sham rTMS group (all r⩽0.211, all P⩾0.198). Further analyses comparing negative symptom responders (⩾20% improvement) and non-responders supported the primary analysis, again only in the active rTMS group (F_{(9, 207)}=2.72, P=0.005, partial η ²=0.106). Heterogeneity in clinical response of negative symptoms in schizophrenia to prefrontal high-frequency rTMS may be related to variability in capacity for structural plasticity, particularly in the left hippocampal region and the precuneus.

Hypertension and Risk of Post-Operative Cognitive Dysfunction (POCD): A Systematic Review and Meta-Analysis

Background:

Post-operative cognitive dysfunction (POCD) occurs frequently after major surgery. Hypertension is well-established as a risk factor for age-related cognitive impairment, but it is unclear whether or not it also increases the risk of POCD.

Objective:

To evaluate the role of hypertension in POCD risk in a systematic review and meta-analysis.

Method:

PubMed, Ovid SP and the Cochrane Database of Systematic Reviews were searched for longitudinal studies of adults undergoing surgery with reporting of hypertension, blood pressure and/or anti-hypertensive treatment associations with POCD as relative risks or odds ratios. Fixed-effects meta-analyses were performed using Review Manager (version 5.3).

Results:

Twenty-four studies on 4317 patients (mean age 63 years) were included. None of the studies had set out to assess hypertension as a risk factor for POCD. Hypertension was used as a categorical predictor throughout and only 2 studies adjusted for potential confounders. Across all 24 studies, hypertension was not significantly associated with POCD risk (RR 1.01; 95% CI 0.93, 1.09; p=0.82), though among 8 studies with >75% males, we found hypertension associations with a 27% increased risk of POCD (RR 1.27, 95% CI 1.07, 1.49; p=0.005).

Conclusion:

Our findings do not support the hypothesis that hypertension is a risk factor for POCD. However, since none of the studies included in our analysis were hypothesis-driven and most did not adjust for potential confounders, further systematic investigations are needed to evaluate the role of hypertension in the epidemiology of POCD.

Association of Common Polymorphisms in the Nicotinic Acetylcholine Receptor Alpha4 Subunit Gene with an Electrophysiological Endophenotype in a Large Population-Based Sample

Variation in genes coding for nicotinic acetylcholine receptor (nAChR) subunits affect cognitive processes and may contribute to the genetic architecture of neuropsychiatric disorders. Single nucleotide polymorphisms (SNPs) in the CHRNA4 gene that codes for the alpha4 subunit of alpha4/beta2-containing receptors have previously been implicated in aspects of (mostly visual) attention and smoking-related behavioral measures. Here we investigated the effects of six synonymous but functional CHRNA4 exon 5 SNPs on the N100 event-related potential (ERP), an electrophysiological endophenotype elicited by a standard auditory oddball. A total of N = 1,705 subjects randomly selected from the general population were studied with electroencephalography (EEG) as part of the German Multicenter Study on nicotine addiction. Two of the six variants, rs1044396 and neighboring rs1044397, were significantly associated with N100 amplitude. This effect was pronounced in females where we also observed an effect on reaction time. Sequencing of the complete exon 5 region in the population sample excluded the existence of additional/functional variants that may be responsible for the observed effects. This is the first large-scale population-based study investigation the effects of CHRNA4 SNPs on brain activity measures related to stimulus processing and attention. Our results provide further evidence that common synonymous CHRNA4 exon 5 SNPs affect cognitive processes and suggest that they also play a role in the auditory system. As N100 amplitude reduction is considered a schizophrenia-related endophenotype the SNPs studied here may also be associated with schizophrenia outcome measures.

Attenuated prefrontal activation during decision-making under uncertainty in schizophrenia: a multi-center fMRI study

Decisions are called decisions under uncertainty when either prior information is incomplete or the outcomes of the decision are unclear. Alterations in these processes related to decisions under uncertainty have been linked to delusions. In patients with schizophrenia, the underlying neural networks have only rarely been studied. We aimed to disentangle the neural correlates of decision-making and relate them to neuropsychological and psychopathological parameters in a large sample of patients with schizophrenia and healthy subjects. Fifty-seven patients and fifty-seven healthy volunteers from six centers had to either indicate via button-press from which of two bottles red or blue balls were drawn (decision-making under uncertainty condition), or indicate whether eight red balls had been presented (baseline condition) while BOLD signal was measured with fMRI. Patients based their decisions on less conclusive evidence and had decreased activations in the underlying neural network, comprising of medial and lateral frontal as well as parietal areas, as compared to healthy subjects. While current psychopathology was not correlated with brain activation, positive symptoms led to longer decision latencies in patients. These results suggest that decision-making under uncertainty in schizophrenia is affected by a complex interplay of aberrant neural activation. Furthermore, reduced neuropsychological functioning in patients was related to impaired decision-making and task performance was modulated by distinct positive symptoms.

DTNBP1 (dysbindin) gene variants: in vivo evidence for effects on hippocampal glutamate status

INTRODUCTION

In linkage and association studies the DTNBP1 gene has been identified as a major susceptibility gene for schizophrenia. Reduced expression of DTNBP1 was found in the hippocampus and prefrontal cortex in post mortem brains of schizophrenic patients. In vitro and animal models provide evidence that the DTNBP1 gene product dysbindin modulates the activity of the neurotransmitter glutamate in hippocampal neurons and is crucial for cell functioning and synaptogenesis. This study is the first to investigate the effects of genetic variants of DTNBP1 on the status of the glutamate system as well as neuronal integrity (N-acetylaspartate, NAA) in the hippocampus and a cortical region, the anterior cingulate cortex (ACC), in humans.

METHODS

In 79 healthy subjects, the association of single nucleotide polymorphisms (SNPs) rs760665 and rs909706 with absolute concentrations of glutamate and NAA in the left hippocampus and the ACC were investigated, using proton magnetic resonance spectroscopy (MRS) at 3 Tesla and a well established quantification procedure.

RESULTS

Hippocampal glutamate concentration was significantly affected by genotype of rs760665 (F=4.406, df=2,p=0.016) and rs909706 (F=3.171,df=2,p=0.048). For the concentration of NAA, a weak association with rs760665 was observed in the contrast analysis. None of the metabolites measured in the ACC showed a significant connection with either genotype.

CONCLUSION

The results support a role of DTNBP1 gene variants in the glutamate neurotransmission system in the human brain at least in the hippocampus. This is compatible to growing evidence of a crucial role of glutamate in the pathobiology of schizophrenia. In addition, the weak association between DTNBP1 genotype and NAA is in line with a regulatory influence of dysbindin on synaptogenesis and neuronal survival.

Hippocampal subfields predict positive symptoms in schizophrenia: first evidence from brain morphometry

Alterations of hippocampal anatomy have been reported consistently in schizophrenia. Within the present study, we used FreeSurfer to determine hippocampal subfield volumes in 21 schizophrenic patients. A negative correlation between PANSS-positive symptom score and bilateral hippocampal subfield CA2/3 as well as CA1 volume was found on high-resolution magnetic resonance images. Our observation opens the gate for advanced investigation of the commonly reported hippocampal abnormalities in schizophrenia in terms of specific subfields.

Association of a variant in the muscarinic acetylcholine receptor 2 gene (CHRM2) with nicotine addiction

Genetic factors contribute to the overall risk of developing nicotine addiction, which is the major cause of preventable deaths in western countries. However, knowledge regarding specific polymorphisms influencing smoking phenotypes remains scarce. In the present study we provide evidence that a common single nucleotide polymorphism (SNP) in the 5' untranslated region of CHRM2, the gene coding for the muscarinic acetylcholine receptor 2 is associated with nicotine addiction. CHRM2 was defined as a candidate gene for nicotine addiction based on previous evidence that linked variations in CHRM2 to alcohol and drug dependence. A total of more than 5,500 subjects representative of the German population were genotyped and assessed regarding their smoking habits. The impact of three SNPs in CHRM2 on smoking behavior/nicotine addiction was investigated using logistic regression models or a quasi-Poisson regression model, respectively. We found the T allele of SNP rs324650 to be associated with an increased risk of smoking/nicotine dependence according to three different models, the recessive models of regular or heavy smokers vs. never-smokers (odds ratio 1.17 in both analyses) and according to the Fagerström index of nicotine addiction. In the analysis stratified by gender this association was only found in females. Our data provide further evidence that variations in CHRM2 may be associated with the genetic risk of addiction in general or with certain personality traits that predispose to the development of addiction. Alternatively, variations in CHRM2 could modulate presynaptic auto-regulation in cholinergic systems and may thereby affect an individual's response to nicotine more specifically.

The tolerability of rTMS treatment in schizophrenia with respect to cognitive function

INTRODUCTION

The purpose of this study was to assess tolerability and safety of high-frequency rTMS with regard to cognitive performance when conducted as "add-on" treatment in chronic schizophrenia in-patients (n=32).

METHODS

Patients, who were on stable antipsychotic treatment, were randomly assigned to verum or sham condition (double-blind). In the verum group, ten sessions of 10 Hz rTMS with a total of 10 000 stimuli were applied over the left dorsolateral prefrontal cortex (PFC) at 110% of motor threshold over a period of two weeks. The sham group received corresponding sham stimulation. RTMS effects on cognitive performance were assessed with a neuropsychological test battery consisting of the following tests: trail making test A and B (TMT), Wisconsin card sorting test (WCST), D2 attention task and the "short test of general intelligence" (KAI).

RESULTS

No statistically significant deterioration of cognitive performance was observed as a result of rTMS treatment. Moreover it was shown that in the verum group patients with a less favourable performance on the WCST at baseline tend to improve after rTMS treatment with regard to psychopathology as opposed to patients in the control group.

DISCUSSION

The stability of cognitive function suggests good tolerability of rTMS treatment in schizophrenia. The absence of evidence for cognitive deterioration could be due to low and short stimulation parameters.

Repetitive transcranial magnetic stimulation for the treatment of negative symptoms in residual schizophrenia: rationale and design of a sham-controlled, randomized multicenter study

Current meta-analysis revealed small, but significant effects of repetitive transcranial magnetic stimulation (rTMS) on negative symptoms in patients with schizophrenia. There is a need for further controlled, multicenter trials to assess the clinical efficacy of rTMS on negative symptoms in schizophrenia in a larger sample of patients. The objective of this multicenter, randomized, sham-controlled, rater- and patient-blind clinical trial is to investigate the efficacy of 3-week 10-Hz high frequency rTMS add on to antipsychotic therapy, 15 sessions per 3 weeks, 1,000 stimuli per session, stimulation intensity 110% of the individual motor threshold) of the left dorsolateral prefrontal cortex for treating negative symptoms in schizophrenia, and to evaluate the effect during a 12 weeks of follow-up. The primary efficacy endpoint is a reduction of negative symptoms as assessed by the negative sum score of the positive and negative symptom score (PANSS). A sample size of 63 in each group will have 80% power to detect an effect size of 0.50. Data analysis will be based on the intention to treat population. The study will be conducted at three university hospitals in Germany. This study will provide information about the efficacy of rTMS in the treatment of negative symptoms. In addition to psychopathology, other outcome measures such as neurocognition, social functioning, quality of life and neurobiological parameters will be assessed to investigate basic mechanisms of rTMS in schizophrenia. Main limitations of the trial are the potential influence of antipsychotic dosage changes and the difficulty to ensure adequate blinding.

Brain activation patterns underlying fast habituation to painful laser stimuli

A painful experience is modified by processes like habituation/antinociception or sensitization. Altered habituation may be one characteristic of chronic pain syndromes. In the present study we sought to investigate the functional magnetic resonance imaging (fMRI) blood oxygen level dependent (BOLD) correlate of rapid habituation to pain using simultaneous single trial electrodermal activity (EDA)/fMRI measurements. A total of N=32 healthy subjects have been investigated. Subjects received painful laser stimulation of the left hand. The fMRI BOLD response was measured simultaneously with continuous EDA recordings. Single trial EDA responses to laser stimulation habituated over time with substantial subject-to-subject differences in the degree and speed of habituation. fMRI BOLD habituation was assessed by contrasting the first half of the experiment against the second half and was found in primary and secondary somatosensory cortices, the insula and the anterior cingulate cortex (ACC). We hypothesized that single trial EDA habituation would reflect BOLD habituation which was investigated separately in subjects with 'faster' (N=15) and 'slower' (N=14) EDA habituation. Significant habituation of the BOLD signal was only found in subjects with 'faster' EDA habituation that was accompanied by a signal increase in the rostral ACC and the periaqueductal grey. Furthermore, subjects with faster EDA habituation provided lower pain ratings. Therefore the EDA habituation profile to painful stimulation may constitute a pain-related (endo)phenotype and may be an informative additional endpoint measure in fMR-imaging of pain, especially when people suffering from chronic pain states in which pain processing is often altered are studied.

Single-trial P3 amplitude and latency informed event-related fMRI models yield different BOLD response patterns to a target detection task

Using single-trial parameters as a regressor in the General Linear Model (GLM) is becoming an increasingly popular method for informing fMRI analysis. However, the parameter used to characterise or to differentiate brain regions involved in the response to a particular task varies across studies (e.g. ERP amplitude, ERP latency, reaction time). Furthermore, the way in which the single-trial information is used in the fMRI analysis is also important. For example, the single-trial parameters can be used as regressors in the GLM or to modify the duration of the events modelled in the GLM. The aim of this study was to investigate the BOLD response to a target detection task when including P3 amplitude, P3 latency and reaction time parameters in the GLM. Simultaneous EEG-fMRI was recorded from fifteen subjects in response to a visual choice reaction time task. Including P3 amplitude as a regressor in the GLM yielded activation in left central opercular cortex, left postcentral gyrus, left insula, left middle frontal gyrus, left insula and left parietal operculum. Using P3 latency and reaction time as an additional regressor yielded no additional activation in comparison with the conventional fMRI analysis. However, when P3 latency or reaction time was used to determine the duration of events at a single-trial level, additional activation was observed in the left postcentral gyrus, left precentral gyrus, anterior cingulate cortex and supramarginal gyrus. Our findings suggest that ERP amplitudes and latencies can yield different activation patterns when used to modify relevant aspects of the GLM.

Electrophysiological subtypes of psychotic states

OBJECTIVE

This research sought neurobiological features common to psychotic states displayed by patients with different clinical diagnoses.

METHOD

Cluster analysis with quantitative electroencephalographic (QEEG) variables was used to subtype drug-naïve, non-medicated, and medicated schizophrenic, depressed and alcoholic patients with psychotic symptoms, from the USA and Germany. QEEG source localization brain images were computed for each cluster.

RESULTS

Psychotic patients with schizophrenia, depression and alcoholism, and drug- naïve schizophrenic patients, were distributed among six clusters. QEEG images revealed one set of brain regions differentially upregulated in each cluster and another group of structures downregulated in the same way in every cluster.

CONCLUSION

Subtypes previously found among 94 schizophrenic patients were replicated in a sample of 390 non-schizophrenic as well as schizophrenic psychotics, and displayed common neurobiological abnormalities. Collaborative longitudinal studies using these economical methods might improve differential understanding and treatment of patients based upon these features rather than clinical symptoms.

Potential clinical targets of repetitive transcranial magnetic stimulation treatment in schizophrenia

Despite the introduction of atypical antipsychotic drugs, treatment-resistant symptoms still represent a serious problem in schizophrenia. Currently, there is evidence from clinical studies suggesting that treatment with repetitive transcranial magnetic stimulation (rTMS) may improve schizophrenia symptoms. Our review provides an overview of clinical rTMS studies in schizophrenic patients. A systematic search of the literature (Cochrane and Medline databases up to December 2005) was conducted. Most studies showed methodological problems due to their explorative character and small sample sizes. In some studies, a treatment effect of high-frequency rTMS applied over the prefrontal cortex was seen with respect to negative symptoms. On the other hand, low-frequency rTMS in the temporal lobe area might lead to a suppression of auditory hallucinations. It is concluded that larger sham-controlled studies are required to allow an adequate assessment of the clinical and neurobiological effects of rTMS in schizophrenic patients. The currently available data provide insufficient evidence to support the use of rTMS as an adjuvant treatment for schizophrenic psychopathology, but encourage further investigation of rTMS as a novel treatment approach.

Aripiprazole Pharmacotherapy of Borderline Personality Disorder

We report three consecutive cases of women with borderline personality disorder with psychotic symptoms, who received pharmacotherapy with the new atypical antipsychotic drug aripiprazole. Therapeutic effects were measured using the SCL-90R (symptom check list) and the BSL (borderline symptom list). We observed different responses to aripiprazole. In the first patient we had to discontinue the drug before we were able to observe any therapeutic effects. The second patient also complained about initial side effects. However, after the dose was lowered, the drug was tolerated and she responded well to aripiprazole with respect to all psychopathological aspects. The third patient did not suffer from any side effects under aripiprazole. She responded partially to the drug. Aripiprazole may have a potential role in the pharmacotherapy of borderline personality disorder and may not only target psychotic symptoms in these patients.

Cortical microcircuits in schizophrenia--the dopamine hypothesis revisited

Strong evidence exists for disturbed functional connectivity of cortical microcircuits--particularly of prefrontal cortex. Dopamine, long implicated in antipsychotic drug effects, is crucially involved in optimizing signal-to-noise ratio of local cortical micro-circuits. This action of dopamine is achieved by means of D1- and D2-receptor-mediated effects on pyramidal and local circuit neurons, which mediate recurrent inhibition and thus contribute to the stability of cortical representations of external and internal stimuli. In schizophrenia, a diminished cortical dopamine D1/D2 activation ratio--in concert with altered GABAergic and glutamatergic transmission--appear to critically interfere with this process.

EEG phenotype in alcoholism: increased coherence in the depressive subtype

OBJECTIVE

Electroencephalography (EEG) power and coherence changes may be trait markers for alcoholism providing clues to brain mechanisms of vulnerability. However, it is unclear whether alpha power and coherence differences reflect reversible toxic or withdrawal effects of alcohol.

METHOD

The EEGs of 10 non-abstinent and 16 long-term abstinent alcoholics (7.7 +/- 5.8 years) and 25 controls were analyzed. Levels of anxiety and depression were assessed by questionnaire.

RESULTS

No statistically significant EEG power differences were observed between groups, although the numerical difference between alcoholics and controls was similar to that previously reported. Bilateral, intrahemispheric, posterior coherences were significantly increased in the alpha and beta frequency bands both in long-term abstinent and non-abstinent alcohol-dependent subjects - particularly when depressiveness was included as a covariate.

CONCLUSION

These results suggest that increased EEG-coherence (cortical synchronization) may serve as endophenotype for alcoholism in conjunction with increased depressiveness and point to a possible involvement of GABAergic and/or glutamatergic neurotransmission.

P300 and LORETA: comparison of normal subjects and schizophrenic patients

It was the aim of the present study 1) to investigate how many cortical activity maxima of scalp-recorded P300 are detected by Low Resolution Electromagentic Tomography (LORETA) when analyses are performed with high time-resolution, 2) to see if the resulting LORETA-solution is in accordance with intracortical recordings as reported by others and 3) to compare the given pattern of cortical activation maxima in the P300-timeframe between schizophrenic patients and normal controls. Current density analysis was performed in 3-D Talairach space with high time resolution i.e. in 6 ms steps. This was done during an auditory choice reaction paradigm separately for normal subjects and schizophrenic patients with subsequent group comparisons. In normal subjects, a sequence of at least seven cortical activation maxima was found between 240-420ms poststimulus: the prefrontal cortex, anterior or medial cingulum, posterior cingulum, parietal cortex, temporal lobe, prefrontal cortex, medial or anterior cingulum. Within the given limits of spatial resolution, this sequential maxima distribution largely met the expectations from reports on intracranial recordings and functional neuroimaging studies. However, localization accuracy was higher near the central midline than at lateral aspects of the brain. Schizophrenic patients less activated their cortex in a widespread area mainly in the left hemisphere including the prefrontal cortex, posterior cingulum and the temporal lobe. From these analyses and comparsions with intracranial recordings as reported by others, it is concluded that LORETA correctly localizes P300-related cortical activity maxima on the basis of 19 electrodes except for lateral cortical aspects which is most likely an edge-phenomenon. The data further suggest that the P300-deficit in schizophrenics involves an extended cortical network of the left hemisphere at several steps in time during the information processing stream.

Event-related potentials and genetic risk for schizophrenia

BACKGROUND

Event-related potentials (ERPs) during an auditory oddball task were investigated in patients with schizophrenia and in their healthy siblings to explore the question of whether abnormalities of two-dimensional topographic scalp-distribution of P300 amplitude and latency relate to genetic risk for schizophrenia. We also examined the P50, N100, and P200-waves, elicited during the same task.

METHODS

We investigated 42 schizophrenic patients, 62 of their healthy siblings, and 34 unrelated normal control subjects with a standard auditory oddball paradigm and 16 electroencephalogram electrodes. Amplitudes and latencies of the ERPs P50, N100, P200, and P300 were topographically analyzed.

RESULTS

In the patients, P300 amplitude was significantly decreased in the range of 54%-58% over the left parietotemporal area. Siblings did not show decreased P300 amplitudes when compared with normal subjects. P300 latencies were unchanged in both groups. No significant group differences were observed for the other event-related potentials.

CONCLUSIONS

In line with previous studies, the P300 amplitude in schizophrenic patients was decreased over the left temporoparietal area; however, we found no evidence for a genetic trait effect in the event-related potential abnormality. Possible reasons for these largely negative findings are discussed.

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.

Reduced event-related current density in the anterior cingulate cortex in schizophrenia

There is good evidence from neuroanatomic postmortem and functional imaging studies that dysfunction of the anterior cingulate cortex plays a prominent role in the pathophysiology of schizophrenia. So far, no electrophysiological localization study has been performed to investigate this deficit. We investigated 18 drug-free schizophrenic patients and 25 normal subjects with an auditory choice reaction task and measured event-related activity with 19 electrodes. Estimation of the current source density distribution in Talairach space was performed with low-resolution electromagnetic tomography (LORETA). In normals, we could differentiate between an early event-related potential peak of the N1 (90-100 ms) and a later N1 peak (120-130 ms). Subsequent current-density LORETA analysis in Talairach space showed increased activity in the auditory cortex area during the first N1 peak and increased activity in the anterior cingulate gyrus during the second N1 peak. No activation difference was observed in the auditory cortex between normals and patients with schizophrenia. However, schizophrenics showed significantly less anterior cingulate gyrus activation and slowed reaction times. Our results confirm previous findings of an electrical source in the anterior cingulate and an anterior cingulate dysfunction in schizophrenics. Our data also suggest that anterior cingulate function in schizophrenics is disturbed at a relatively early time point in the information-processing stream (100-140 ms poststimulus).

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.