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Biomedical subjects

Konrad Maurer

Publications and source records attributed to Konrad Maurer.

At least 19 recordsLinked to original sources
PubMed2007

HTR2C and HTR1A gene variants in German and Italian suicide attempters and completers.

The serotonin 2C (HTR2C) and 1A (HTR1A) receptors have been involved in suicide-related behaviors. We studied gene variants of both receptors in suicide attempters and completers. The sample was composed of 167 German suicide attempters (affective spectrum n = 107, schizophrenia spectrum n = 35, borderline personality disorder n = 25), 92 Caucasian individuals who committed suicide, 312 German healthy subjects, 152 Italian suicide attempters (major depression n = 68 and bipolar disorder n = 84), and 131 Italian healthy volunteers. HTR2C (SNP: rs547536, rs2192372, rs6318, rs2428707, rs4272555, rs1801412) and HTR1A (SNP: rs1423691, rs878567, and rs6295) variants were analyzed in the German sample. HTR2C rs6318 and HTR1A rs6295 were analyzed in the Italian sample. Haplotype analysis in relation to suicidal behaviors did not reveal any significant association. Single markers and haplotypes were not or only marginally associated with other related features, such as violence of suicide attempt, family history for suicide attempt or State-Trait Anger Expression Inventory (STAXI) and Questionnaire for Measuring Factors of Aggression (FAF) scores. In conclusion, our study does not support the notion that HTR2C and HTR1A gene variants are major contributors to suicide-, anger-, or aggression-related behaviors in our sample.

Adolescent↗
PubMed2006

ABCG1 gene variants in suicidal behavior and aggression-related traits.

The ABCG1 transporter seems to be involved in human cholesterol and sterol homeostasis. As alterations in cholesterol homeostasis have been widely linked to aggression, violence and suicidal behavior, we considered ABCG1 as a candidate gene for these traits. We studied 5 gene variants of ABCG1 in a sample of 571 suicide attempters, healthy controls and suicide completers. We also analyzed the relation to aggression-related traits, assessed by STAXI and FAF. Regarding the genotypes, there was no association with completed or attempted suicide with the tested SNPs. Regarding alleles, only one SNP (rs1044317) showed a slight association with suicide attempters in comparison to the controls. Interestingly, rs225374 G allele carriers had higher scores on the STAXI subscales "State Anger" and "Anger Out", as well as on the FAF subscales "Spontaneous Aggression", "Irritability" and "Aggression". Carriers of the rs914189 G allele scored higher on the FAF subscales "Spontaneous Aggression", "Reactive Aggression" and "Aggression". Carriers of the rs1044317 G allele had lower scores for STAXI "Trait Anger" and "Trait Temperament", and higher scores for STAXI "Anger Control". Our results provide evidence that the ABCG1 may influence aggression-related traits. Given that these represent intermediate phenotypes of suicidal behavior, ABCG1 might also act on suicidal behavior through these traits. The observed associations warrant further replications.

ATP Binding Cassette Transporter, Subfamily G, Mem↗
PubMed2006

Dysfunctional long-range coordination of neural activity during Gestalt perception in schizophrenia.

Recent theoretical and empirical research on schizophrenia converges on the notion that core aspects of the pathophysiology of the disorder may arise from a dysfunction in the coordination of distributed neural activity. Synchronization of neural responses in the beta-band (15-30 Hz) and gamma-band range (30-80 Hz) has been implicated as a possible neural substrate for dysfunctional coordination in schizophrenia. To test this hypothesis, we examined the electroencephalography (EEG) activity in 19 patients with a Diagnostic and Statistical Manual of Mental Disorder, edition IV criteria, diagnosis of schizophrenia and 19 healthy control subjects during a Gestalt perception task. EEG data were analyzed for phase synchrony and induced spectral power as an index of neural synchronization. Schizophrenia patients were impaired significantly in the detection of images that required the grouping of stimulus elements into coherent object representations. This deficit was accompanied by longer reaction times in schizophrenia patients. Deficits in Gestalt perception in schizophrenia patients were associated with reduced phase synchrony in the beta-band (20-30 Hz), whereas induced spectral power in the gamma-band (40-70 Hz) was mainly intact. Our findings suggest that schizophrenia patients are impaired in the long-range synchronization of neural responses, which may reflect a core deficit in the coordination of neural activity and underlie the specific cognitive dysfunctions associated with the disorder.

Action Potentials↗
PubMed2006

Treating auditory hallucinations by transcranial magnetic stimulation: a randomized controlled cross-over trial.

BACKGROUND: In a previous functional magnetic resonance imaging study, the authors succeeded in demonstrating the activation of Heschl's gyrus during auditory hallucinations (AH). OBJECTIVES: This study aims to treat AH specifically by repetitive transcranial magnetic stimulation (rTMS). METHODS: 16 patients with AH were included in a randomized, cross-over, sham-controlled trial. 1 Hz rTMS was administered over the left and right temporo-parietal cortex and sham position, respectively, on 5 consecutive days; 900 stimuli each, strength 100% of motor threshold. Using the Psychotic Symptom Rating Scales (PSYRATS), the hallucinations during the stimulation periods and 4-week follow-ups were quantified. Electroencephalograms (EEG) were acquired before and after each period. RESULTS: Treatment responses were observed after left hemisphere rTMS only. The 5 patients who showed a response did so already after 2 days. However, group mean hallucination scores did not differ across treatment conditions. No significant changes were found in EEG after rTMS. CONCLUSIONS: A subgroup of patients suffering from AH benefits soon after treatment start from rTMS over the left superior temporal gyrus as revealed by the decrease of AH scores compared to right-sided and sham procedures.

Analysis of Variance↗
PubMed2006

Mental chronometry of working memory retrieval: a combined functional magnetic resonance imaging and event-related potentials approach.

We used the combination of functional magnetic resonance imaging and event-related potentials to decompose the processing stages (mental chronometry) of working memory retrieval. Our results reveal an early transient activation of inferotemporal cortex, which was accompanied by the onset of a sustained activation of posterior parietal cortex. We furthermore observed late transient responses in ventrolateral prefrontal cortex and late sustained activity in medial frontal and premotor areas. We propose that these neural signatures reflect the cognitive stages of task processing, perceptual evaluation (inferotemporal cortex), storage buffer operations (posterior parietal cortex), active retrieval (ventrolateral prefrontal cortex), and action selection (medial frontal and premotor cortex). This is also supported by their differential temporal contribution to specific subcomponents of the P300 cognitive potential.

Adult↗
PubMed2005

Functional activation imaging in aging and dementia.

With life expectancy increasing continuously, the effects of neurodegeneration on brain function are a topic of ever increasing importance. Thus there is a need for tools and models that probe both the functional consequences of neurodegenerative processes and compensatory mechanisms that might occur. As neurodegenerative burden and compensatory mechanisms may change over time, these tools will ideally be applied multiple times over the lifespan. Specifically, in order to elucidate whether brain-activation patterns in Alzheimer's disease (AD) and in healthy aging follow general rules in the context of degeneration and compensation, it is necessary to compare functional brain-activation patterns during different states of neurodegeneration. This article integrates the findings of functional activation studies at different stages of neurodegeneration: in healthy aging, in subjects at high risk of developing dementia, in subjects with mild cognitive impairment (MCI), and in patients suffering from AD. We review existing theoretical models that aim to explain the underlying mechanisms of functional activation changes in aging and dementia, and we propose an integrative account, which allows for different neural response patterns depending on the amount of neuronal damage and the recruitment of compensatory pathways.

Aged↗
PubMed2005

Axis I disorders and personality disorders as risk factors for suicide.

There is a lack of psychological autopsy studies assessing the influence of axis I disorders on axis II disorders as risk factors for suicide. Therefore, we investigated the association between personality disorders, axis I disorders, and suicide. Psychiatric disorders were evaluated by a semi-structured interview including the Structured Clinical Interview for DSM-IV Axis I (SCID-I) and Personality Disorders (SCID-II) in 163 completed suicides (mean age 49.6 +/- 19.3 years; 64.4% men) and by personal interview in 396 population-based control persons (mean age 51.6 +/- 17.0 years; 55.8% men). In both genders, suicides significantly more often had personality disorders of all clusters than controls, also after adjustment for axis I disorders (p < 0.001, each). In addition, alcohol-related disorders, major depression, and co-occurrence of personality disorders of more than one cluster (men: OR = 16.13; women: OR = 20.43) remained independent predictors for suicide in both genders, "pure" cluster B personality disorders only in women and "pure" cluster C personality disorders only in men. In both genders, co-occurrence of personality disorders of more than one cluster contributed to risk of completed suicide after control for axis I psychiatric disorders and has to be considered as an independent risk factor for suicide.

Adult↗
PubMed2005

Nicotine use in suicides: a case-control study.

PURPOSE: Despite of higher rates of substance-related disorders in psychiatric patients and suicides than in the general population, there is no clear specificity to the relationship between nicotine use and other psychiatric disorders for suicide risk. METHODS: One hundred and sixty-three suicides (mean age 49.8 +/- 19.3 years; 64.4% males; using psychological autopsy method) and 396 control persons (mean age 51.6 +/- 17.0 years; 55.8% males) were assessed with a standardised semi-structured interview including SCID-I and SCID-II (for DSM-IV). Suicides and controls were compared in terms of nicotine consumption and psychiatric disorders. Logistic regression was used to evaluate the interactions of tobacco consumption with psychiatric disorders. RESULTS: Suicides were significantly more often current smokers and heavy users of cigarettes (> 20 cigarettes per day; P < 0.001, each). Alcohol dependence, other axis I disorders than substance-related disorders, and cluster B personality disorder(s) remained independent predictors for suicide in both genders, current nicotine consumption only in men (OR = 2.6, 95% CI 1.3-5.2). DISCUSSION AND CONCLUSIONS: In males, but not in females, nicotine consumption contributed to risk of completed suicide after control for psychiatric disorders and has to be considered as independent risk factor for suicide.

Autopsy↗
PubMed2004

Detection of alcohol consumption in suicides.

Screening instruments for detection of alcohol consumption, abuse, and dependence for use in psychological autopsy studies with case control design are not validated. Therefore, interrater and test-retest reliability of the Luebeck Alcohol Dependence and Abuse Screening Test (LAST) and the usability of this test for the psychological autopsy method were investigated. Alcohol consumption was evaluated by a semi-structured interview including the Structured Clinical Interview for DSM-IV Axis I (SCID-I) and the LAST in 163 completed suicides (mean age 49.6 +/- 19.3 years; 64.4% men) and by personal interview in 396 population-based controls (mean age 51.6 +/- 17.0 years; 55.8% men). Of the controls, 35 were additionally assessed by interviewing informants; these results were compared with those generated by personal interview. Comparison of LAST scores by personal and informant's interview of controls generated a Spearman correlation coefficient of 0.74 (P < 0.0001). The LAST (7 item-version, cut-off of 2) revealed high sensitivity and specificity for alcohol abuse and dependence, in both controls and suicides. LAST scores were significantly associated with high, frequent, and hazardous alcohol consumption (P < 0.001) in suicides. Our findings provide support for reliability and validity of identifying individuals with alcohol dependence and abuse obtained through the best-estimate method using the LAST. This 7-item questionnaire can be recommended as a useful tool for the psychological autopsy procedure in postmortem research.

Adult↗
PubMed2004

Concordance of DSM-IV Axis I and II diagnoses by personal and informant's interview.

The validity and reliability of using psychological autopsies to diagnose a psychiatric disorder is a critical issue. Therefore, interrater and test-retest reliability of the Structured Clinical Interview for DSM-IV Axis I and Personality Disorders and the usefulness of these instruments for the psychological autopsy method were investigated. Diagnoses by informant's interview were compared with diagnoses generated by a personal interview of 35 persons. Interrater reliability and test-retest reliability were assessed in 33 and 29 persons, respectively. Chi-square analysis, kappa and intraclass correlation coefficients, and Kendall's tau were used to determine agreement of diagnoses. Kappa coefficients were above 0.84 for substance-related disorders, mood disorders, and anxiety and adjustment disorders, and above 0.65 for Axis II disorders for interrater and test-retest reliability. Agreement by personal and relative's interview generated kappa coefficients above 0.79 for most Axis I and above 0.65 for most personality disorder diagnoses; Kendall's tau for dimensional individual personality disorder scores ranged from 0.22 to 0.72. Despite of a small number of psychiatric disorders in the selected population, the present results provide support for the validity of most diagnoses obtained through the best-estimate method using the Structured Clinical Interview for DSM-IV Axis I and Personality Disorders. This instrument can be recommended as a tool for the psychological autopsy procedure in post-mortem research.

Adjustment Disorders↗
PubMed2004

Targets of antidementive therapy: drugs with a specific pharmacological mechanism of action.

Diagnosis and therapy of dementia have made considerable progress in recent years. Drugs have been developed which improve cognitive performance, delay the loss of abilities of daily living and prevent early nursing home placement in a considerable number of patients. With the various pharmacological and non-pharmacological approaches, effective treatment options of AD are available at present and the therapeutic potential will even increase in future. Thus, the treatment of dementia should more focused and explicit in its goals for the doctor, the patient and the relatives. Therapeutic targets must be defined on the basis of the individual needs and deficits and with regard to different levels of the disease process. Ideally, treatment should always aim at an etiological and/or a pathophysiological level. At present, however, aiming at the neurotransmitter level, the core syndrome of cognitive deficits can be approached by treatment options. Further therapeutic targets can be defined on the level of activities of daily living, following a resource focused approach, as well as on the level of behavioral disturbances. Additional therapeutic targets should be seen under a humanitarian or palliative perspective. And finally, family members are also targets for therapy in dementia, even if such therapy is not directed towards the demented patient. All these treatment targets have to be evaluated and adapted under the perspective of time because prominent symptoms in AD change considerably with disease progression. Selection and adaptation of medication becomes easier if such targets are considered and if therapeutic effects are monitored target-specifically.

Alzheimer Disease↗
PubMed2003

Brain metabolism in Alzheimer disease and vascular dementia assessed by in vivo proton magnetic resonance spectroscopy.

Proton magnetic resonance spectroscopy (MRS) allows the assessment of various cerebral metabolites non-invasively in vivo. Among 1H MRS-detectable metabolites, N-acetyl-aspartate and N-acetyl-aspartyl-glutamate (tNAA), trimethylamines (TMA), creatine and creatine phosphate (tCr), inositol (Ins) and glutamate (Gla) are of particular interest, since these moieties can be assigned to specific neuronal and glial metabolic pathways, membrane constituents, and energy metabolism. In this study on 94 subjects from a memory clinic population, 1H MRS results (single voxel STEAM: TE 20 ms, TR 1500 ms) on the above metabolites were assessed for five different brain regions in probable vascular dementia (VD), probable Alzheimer's disease (AD), and age-matched healthy controls. In both VD and AD, ratios of tNAA/tCr were decreased, which may be attributed to neuronal atrophy and loss, and Ins/tCr-ratios were increased indicating either enhanced gliosis or alteration of the cerebral inositol metabolism. However, the topographical distribution of the metabolic alterations in both diseases differed, revealing a temporoparietal pattern for AD and a global, subcortically pronounced pattern for VD. Furthermore, patients suffering from vascular dementia (VD) had remarkably enhanced TMA/tCr ratios, potentially due to ongoing degradation of myelin. Thus, the metabolic alterations obtained by 1H MRS in vivo allow insights into the pathophysiology of the different dementias and may be useful for diagnostic classification.

Aged↗
PubMed2003

Cerebral networks linked to the event-related potential P300.

P300 is an event-related potential that is elicited by an oddball paradigm. In several neuropsychiatric diseases, differences in latencies and amplitude compared to healthy subjects have been reported. Because of its clinical significance, several investigations have tried to elucidate the intracranial origins of the P300 component. In the present study we could demonstrate a network of P300 generators. Investigated were 15 healthy subjects with an acoustical oddball paradigm within a fMRI block design, which enabled us to exclude attention or acoustical processing effects. The inferior and middle frontal, superior temporal, lower parietal cortex, the insula and the anterior cingulum were significantly activated symmetrical in both hemispheres.

Acoustic Stimulation↗
PubMed2003

Impact of aging: sporadic, and genetic risk factors on vulnerability to apoptosis in Alzheimer's disease.

The identification of specific genetic (presenilin-1 [PS1] and amyloid precursor protein [APP] mutations) and environmental factors responsible for Alzheimer's disease (AD) has revealed evidence for a shared pathway of neuronal death. Moreover, AD-specific cell defects may be observed in many other nonneuronal cells (e.g., lymphocytes). Thus, lymphocytes may serve as a cellular system in which to study risk factors of sporadic, as well as genetic AD in vivo. The aim of our present study was to clarify whether lymphocytes bearing genetic or sporadic risk factors of AD share an increased susceptibility to cell death. Additionally we examined whether a cell typespecific vulnerability pattern was present and how normal aging, the main risk factor of sporadic AD, contributes to changes in susceptibility to cell death. Here, we report that lymphocytes affected by sporadic or genetic APP and PS1 AD risk factors share an increased vulnerability to cell death and exhibit a similar cell type-specific pattern, given that enhanced vulnerability was most strongly developed in the CD4+ T-cell subtype. In this paradigm, sporadic risk factors revealed the highest impact on cell type-specific sensitivity of CD4+ T cells to apoptosis. In contrast, normal aging results in an increased susceptibility to apoptosis of both, CD4+ and CD8+ T cells.

Age Factors↗