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K Mersmann

Publications and source records attributed to K Mersmann.

6 recordsLinked to original sources
PubMed2001

Enhanced semantic priming in thought-disordered schizophrenic patients using a word pronunciation task.

Previous research on semantic priming in schizophrenia has produced contradictory findings. For the present study, it was intended to resolve some of the ambiguities in the literature. Using a semantic priming task with word pronunciation, evidence is provided that thought-disordered schizophrenic (TD) patients exhibit significantly increased semantic priming as compared to healthy and psychiatric controls. Results suggest that enhanced semantic priming is not confined to tasks that require lexical decision. Moreover, results indicate that TD schizophrenic patients suffer from a decay of hierarchical thinking, i.e. TD schizophrenics reveal a tendency to process the less meaningful rather than the dominant aspects of external information. Priming effects for the inferior meaning of homograph words (for example, 'dance' is an inferior, and 'game' is a superior associate of the word 'ball') were significantly greater compared to healthy controls and non-TD schizophrenics. Results were not moderated by sociodemographic background variables, psychomotor slowing and psychopathological symptoms other than thought disorder.

Adult↗
PubMed2001

Neuropsychological correlates of schizophrenic syndromes in patients treated with atypical neuroleptics.

There is widespread evidence that schizophrenic symptomatology is best represented by three syndromes (positive, negative, disorganized). Both the disorganized and negative syndrome have been found to correlate with several neurocognitive dysfunctions. However, previous studies investigated samples predominantly treated with typical neuroleptics, which frequently induce parkinsonian symptoms that are hard to disentangle from primary negative symptoms and may have inflated correlations with neurocognition. A newly developed psychopathological instrument called the Positive and Negative and Disorganized Symptoms Scale (PANADSS) was evaluated in 60 schizophrenic patients. Forty-seven participants treated with atypical neuroleptics performed several neurocognitive tasks.A three-factor solution of schizophrenic symptomatology emerged. Negative symptomatology was associated with diminished creative verbal fluency and digit span backward, whereas disorganization was significantly correlated with impaired Stroop, WCST and Trail-Making Test B performance.Data suggest that disorganization is associated with tasks that demand executive functioning. Previous findings reporting correlations between negative symptomatology and neurocognition may have been confounded by the adverse consequences of typical neuroleptics.

Acute Disease↗
PubMed2001

'Hyper-priming' in thought-disordered schizophrenic patients.

BACKGROUND: A number of studies have suggested that indirect semantic priming is enhanced in thought-disordered schizophrenics. However, research on direct semantic priming has produced conflicting results. The aim of the present study was to resolve some of the ambiguities of previous findings. METHODS: For the present study, 44 schizophrenic patients were split according to the presence of associative loosening into a positive thought-disordered (TD) and non-positive thought-disordered (NTD) group. Thirty healthy subjects and 36 psychiatric patients served as controls. RESULTS: Schizophrenics displayed increased indirect semantic priming compared with psychiatric controls. When subtyping the sample, TD-patients exhibited significantly enhanced indirect semantic priming compared with healthy and psychiatric controls as well as NTD-patients. Overall slowing was found to be independent of priming effects. Medication, age and chronicity of the schizophrenic illness did not modulate priming. CONCLUSIONS: In line with Spitzer and Maher it is inferred that disinhibited semantic networks underlie formal thought disorder in schizophrenia. For future research, it would be appropriate to: employ indirect semantic priming rather than direct semantic priming conditions; and, pay more attention to potential moderators of the priming effect, most importantly, the prime display duration and the length of the stimulus onset asynchrony.

Adult↗
PubMed2001

[Association norms for 68 German homonyms].

Norms for 68 German homophonic homographs were collected in a normal population comprising 100 subjects. Frequency and polarity as well as U-scores (index of ambiguity) are presented. 49 of the words revealed a clear dominance for only one meaning. 7 homophonic homographs were balanced, and for 12 words less than 5% of all associations were given for each of the inferior meanings. Studies 2a and 2b are a replication of previous findings on the resolution of semantic ambiguity. Inhibition effects were revealed for discordant triplet conditions which contained a long interstimulus interval between homograph and target, whereas an (insignificant) facilitation effect occurred for trials with a shorter interval. Results of study 2 are in line with context-sensitive models which claim that after the initial activation of all meanings of a homograph a context-guided process leads to a suppression of context-irrelevant homograph information.

Adult↗
PubMed1995

Purine functional groups in essential residues of the hairpin ribozyme required for catalytic cleavage of RNA.

Synthetic chemistry techniques have been used to study the functional group requirements of the essential purine residues in hairpin ribozyme cleavage. Three-stranded ribozymes were prepared that had functional group deletions or alterations at single purine sites within loops A and B of the hairpin, and the kinetics of cleavage were compared to those of the unmodified ribozyme. Adenosine analogues used were purine riboside and N7-deazaadenosine, and guanosine analogues used were inosine, N7-deazaguanosine, and O6-methylguanosine. In many cases, introduction of one of these analogues caused substantial loss of ribozyme cleavage activity. Most of the impairments of activity were found to be due to changes in kcat rather than in KM. The losses corresponded in magnitude to loss of at least one hydrogen bond, and the results were rationalized in terms of removal of potential cross-strand hydrogen bonds as well as potential hydrogen bonds between loops A and B. A new secondary structure model for loop B was proposed. Finally, the magnesium ion dependence of cleavage was studied for the modified ribozymes and compared to that of the unmodified ribozyme. It is proposed that magnesium binds in the ground state to the N7-positions of G + 1 and A43 and in the transition state to the N7-position at A9. The results provide further evidence for the folding of the two arms of the hairpin so that in the active conformation loops A and B approach closely to form a specific three-dimensional structure with a magnesium ion (or ions) placed between the loops, making contacts in the ground state and in the transition state.

Adenosine↗