Biomedical subjects

T Merten

Publications and source records attributed to T Merten.

10 recordsLinked to original sources

PubMed2007

[Negative response bias and the validity of personality profiles in neuropsychiatric assessment].

Although symptom validity tests have become available to German test users during the last few years, there is very little research into measures of negative response bias in personality assessment. The present study investigates the effects of negative response bias as measured by the Word Memory Test (WMT) and the Structured Inventory of Malingered Symptomatology (SIMS) on self-report personality scales. A retrospective analysis was performed on data from 93 patients who had undergone neuropsychiatric assessment in the context of independent medical examination. Complete data sets were available for the WMT, the SIMS, and the Freiburg Personality Inventory-Revised (FPI-R). Significant differences were found for a number of personality scales, depending on WMT and SIMS classification. The FPI-R validity scale (Openness) was linked to neither WMT nor SIMS, whereas the results in the latter two instruments showed a significant overlap of classification results (phi=0.44). A principal axis analysis yielded corresponding results. It is concluded that self-report personality measures may be considerably distorted by negative response bias. FPI-R Openness scale scores do not allow any interpretation in terms of negative response bias. More effort should be directed in German-speaking countries towards the development and validation of appropriate validity scales.

Adult↗

PubMed2004

[Neuropsychological assessment of suboptimal performance: the Word Memory Test].

Although malingering, suboptimal cognitive performance, and negative response bias represent very problematic confounds in diagnostic work with a number of neurological and some psychiatric illnesses, the evaluation of these tendencies has not yet become common practice in German-speaking countries. Only a limited number of adequately validated instruments are available. The German adaptation of the Word Memory Test (WMT), an internationally renowned test for use in the area of neurocognitive disturbances, is presented. The first study compares performance of a healthy experimental group of malingerers ( n=100) with a healthy control group after standard test instructions ( n=27). The WMT achieved a 100% correct identification of group membership. The second study was carried out with a sample of mentally retarded patients ( n=32) and showed that the WMT was likewise able to identify high performance motivation in almost all of the cases. Only one patient was incorrectly classified. These results are commensurate with the highly sensitive parameters that have been reported for the WMT in North America. With the introduction of the WMT into neuropsychological diagnostic work in Germany, it will become easier to meet quality standards that have become customary internationally.

Adult↗

PubMed2002

[Neuropsychological assessment of malingering].

Current problems and neuropsychological assessment strategies of malingering detection (assessment of negative response bias or non-optimal test behaviour) are reviewed. First, the paper discusses major conceptual problems inherent in the definition of malingering, factitious disorders, and somatoform disorders. Traditional and modern test approaches and diagnostic procedures are reviewed. Two case vignettes illustrate the application of particular strategies for malingering assessment. In German speaking countries, malingering research has not yet aroused profound interest comparable to that in English speaking countries. Diagnostic standards and instruments still have to be refined.

Humans↗

PubMed2000

Actin-associated protein synaptopodin in the rat hippocampal formation: localization in the spine neck and close association with the spine apparatus of principal neurons.

Dendritic spines are sites of synaptic plasticity in the brain and are capable of remodeling their shape and size. However, little is known about the cellular mechanisms that regulate spine morphology and motility. Synaptopodin is a recently described actin-associated protein found in renal podocytes and dendritic spines (Mundel et al. J Cell Biol. [1997] 139:193-204), which is believed to play a role in spine plasticity. The present study analyzed the distribution of synaptopodin in the hippocampal formation. In situ hybridization histochemistry revealed a high constitutive expression of synaptopodin mRNA in the principal cell layers. Light microscopic immunohistochemistry showed that the protein is distributed throughout the hippocampal formation in a region- and lamina-specific manner. Postembedding immunogold histochemistry demonstrated that synaptopodin is exclusively present in dendrites and spines, specifically in the spine neck in close association with the spine apparatus. Spines lacking a spine apparatus are not immunoreactive for synaptopodin. These data suggest that synaptopodin links the spine apparatus to actin and may thus be involved in the actin-based plasticity of spines.

Actins↗

PubMed2000

The chondroitin sulphate proteoglycan brevican is upregulated by astrocytes after entorhinal cortex lesions in adult rats.

The chondroitin sulphate proteoglycan brevican is one of the most abundant extracellular matrix molecules in the adult rat brain. It is primarily synthesized by astrocytes and is believed to influence astroglial motility during development and under certain pathological conditions. In order to study a potential role of brevican in the glial reaction after brain injury, its expression was analysed following entorhinal cortex lesion in rats (12 h, 1, 2, 4, 10, 14 and 28 days and 6 months post lesion). In situ hybridization and immunohistochemistry were employed to study brevican mRNA and protein, respectively, in the denervated outer molecular layer of the fascia dentata and at the lesion site. In both regions brevican mRNA was upregulated between 1 and 4 days post lesion. The combination of in situ hybridization with immunohistochemistry for glial fibrillary acidic protein demonstrated that many brevican mRNA-expressing cells are astrocytes. In the denervated zone of the fascia dentata, immunostaining for brevican was increased by 4 days, reached a maximum by 4 weeks and remained detectable up to 6 months post lesion. Electron microscopic immunocytochemistry showed that brevican is a component of the extracellular matrix compartment. At the lesion site a similar time course of brevican upregulation was observed. These data demonstrate that brevican is upregulated in areas of brain damage as well as in areas denervated by a lesion. They suggest a role of brevican in reactive gliosis and are compatible with the hypothesis that brevican is involved in the synaptic reorganization of denervated brain areas.

Acetylcholinesterase↗

PubMed1999

Entorhinal cortex lesion in adult rats induces the expression of the neuronal chondroitin sulfate proteoglycan neurocan in reactive astrocytes.

The chondroitin sulfate proteoglycan neurocan is a major component of brain extracellular matrix during development. Neurocan is primarily synthesized by neurons and has the ability to interact with cell adhesion molecules involved in the regulation of cell migration and axonal growth. Within the first weeks postnatally, neurocan expression is strongly downregulated. To test whether neurocan is reexpressed in areas of axonal growth (sprouting) after brain injury, the time course of neurocan expression was analyzed in the denervated fascia dentata of the rat after entorhinal cortex lesion (12 hr; 1, 2, 4, and 10 d; 2 and 4 weeks; and 6 months after lesion). In the denervated zone, immunohistochemistry revealed neurocan-positive astrocytes by 2 d after lesion and a diffuse labeling of the extracellular matrix at all later time points. Electron microscopy confirmed the deposition of neurocan in the extracellular matrix compartment. In situ hybridization demonstrated a strong upregulation of neurocan mRNA within the denervated outer molecular layer 1 and 4 d after lesion. The combination of in situ hybridization with immunohistochemistry for glial fibrillary acidic protein demonstrated that the neurocan mRNA-expressing cells are astrocytes. These data demonstrate that neurocan is reexpressed in the injured brain. In contrast to the situation during development, astrocytes, but not neurons, express neurocan and enrich the extracellular matrix with this molecule. Similar to the situation during development, neurocan is expressed in an area of active axon growth, and it is suggested that neurocan acts to maintain the boundaries of the denervated fascia dentata after entorhinal cortex lesion.

Animals↗

PubMed1999

[Neuropsychology of normal pressure hydrocephalus].

Although dementia is described as one of the constituent characteristics of normal pressure hydrocephalus (NPH), alongside gait disturbances and urinary incontinence, there is a rather limited number of controlled studies concerning neuropsychological deficits in the disease. A wide range of psychopathologically relevant symptoms have been described, but the common features of most cases include mental and motor slowing, apathy, emotional indifference, anosognosia, memory and attentional impairment. A number of other functional deficits such as dyslexia, dysgraphia, acalculia, apraxia can also frequently be found. Some emphasis is put on the work of J. de Mol (Brussels) which appears to be most important for the study of neuropsychological symptoms in NPH patients. The methodological standard of a number of studies has been found to be rather low, and yet a sound neuropsychological investigation may be of utmost importance for the diagnosis and neurosurgical outcome assessment. Concerning morphological correlates of the functional deficits in NPH, various hypotheses have been formulated, but it is argued that symptoms can neither be described as predominantly "diffuse" in nature, nor can they be reduced to unilocular dysfunctions. Recommendations for future research strategies are formulated.

Adolescent↗

PubMed1999

An analysis of the Hooper Visual Organization Test with neurological patients.

An item analysis of the Hooper Visual Organization Test (VOT) was performed using the test protocols of 320 German-speaking neurological patients with a mean age of 51.3 years. All patients presented some form of cerebral pathology. The sample yielded a mean test score of 18.8 (SD = 6.2). Estimates of internal consistency of the total scale yielded acceptable results (>.88). Although the VOT was judged to be a useful instrument for assessing visuoperceptual and visuospatial-organizational dysfunction, item characteristics of the test are not satisfactory. In particular, the item ranking does not correspond to the order of difficulty. Moreover, in their current form, scoring rules of a number of items seem to be arbitrary and not founded on empirical data. A revision of the VOT is proposed to improve its psychometric properties.

Adult↗

PubMed1992

[Word association and schizophrenia--an empirical study].

Since Bleuler's (1911) work on dementia praecox, numerous studies on associative disturbances in schizophrenics have been published. Methodological flaws and difficulties in interpreting the disturbances consistently have brought about a certain dilemma: they are unanimously considered a basic disorder in schizophrenia, but the problem of their reliable evaluation has remained unanswered. 43 schizophrenics, 15 affective psychotics, and 46 normals were investigated in order to compare different forms of the word association test (WAT). The schizophrenics gave less common responses than the normals in the free association task. However, the two groups differed more widely in their performance when asked to respond "individually", "commonly", or using a multiple-choice associative test. The affective psychotics were similar in their response behaviour, partly to the schizophrenics (free and common response conditions; multiple-choice test), partly to the normals (individual response condition). The relationship of the WAT to personality characteristics (Eysenck's psychoticism), the influence of psychopathology and the course of the disease, the patients' well-being and self-report of speech and thought disorders are discussed.

Acute Disease↗

PubMed1990

[The Carroll Scale for Depression--the German version and validation].

The Carroll Rating Scale for Depression, first published by Carroll et al. in 1981, has been translated into German. 28 out-patients and a control-group of 28 normals were submitted to the CRS and, for purposes of validation, to the BECK scale and the diagram HARD. The Carroll Rating Scale is directly based on the Hamilton Rating Scale, but, in contrast, it represents a self rating that should be useful for longitudinal studies.

Adult↗