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Biomedical subjects

Georg Wiedemann

Publications and source records attributed to Georg Wiedemann.

12 recordsLinked to original sources
PubMed2006

Disorganization and cognitive impairment in schizophrenia: independent symptom dimensions?

Cognitive deficits are increasingly considered as essential in schizophrenic disorders. Positive symptoms and cognitive deficits have been found to be independent, whereas negative symptoms show only weak correlations to cognitive impairment. However, the relationship to a third symptom dimension, disorganization, is yet unclear. In a sample of n = 151 schizophrenia inpatients (DSM-IV/SCID) we assessed cognitive impairment using a comprehensive neuropsychological test battery and symptoms of schizophrenia applying the Positive and Negative Syndrome Scale (PANSS). Factor analyses resulted in three neuropsychological (attention, memory, abstraction) and five symptom factor scores (negative, impulsiveness, positive, disorganization, depression). The disorganization factor did not correlate significantly with any of the neuropsychological factor scores. Even after controlling for different demographic and clinical variables partial correlation coefficients did not reach a significant level. Thus, we could not confirm the previously reported associations between disorganization and measures of cognitive impairment. Despite a considerable conceptual overlap between interview based symptom ratings and classic neuropsychological tests the empirical association is limited. Our results suggest that disorganization and cognitive impairment represent different symptom dimensions.

Adult↗
PubMed2006

Phylo- and ontogenetic fears and the expectation of danger: differences between spider- and flight-phobic subjects in cognitive and physiological responses to disorder-specific stimuli.

To compare specific phobias with an assumed phylogenetic or ontogenetic origin in responses to fear-relevant (FR) stimuli, 17 spider- and 17 flight-phobic participants were exposed to pictures of spiders, flight accidents, or mushrooms randomly followed by either a startling noise or nothing else. While both groups showed a disorder-specific expectancy bias, only spider-phobic participants exhibited a disorder-specific covariation bias. Spider-phobic participants also showed enhanced skin conductance responses (SCRs), event-related brain potentials (ERPs), and startle responses triggered by disorder-specific FR pictures while flight-phobic participants showed only disorder-specific enhanced SCRs. In sum, our direct comparison between ontogenetic and phylogenetic phobias revealed that the former is characterized by biased and enhanced responses triggered by disorder-specific FR stimuli presumably based on a biological preparedness.

Adult↗
PubMed2005

Electrocortical evidence for an early abnormal processing of panic-related words in panic disorder patients.

Panic patients are hypothesized to have particularly elaborated cortical networks for panic-related stimuli, and this characteristic should be associated with an abnormal automatic processing of these stimuli. Panic-related and neutral words were presented to 25 panic patients and 25 matched healthy controls either at individually determined perception thresholds (threshold condition) or for 1000 ms (above threshold condition). Word recognition for words presented at perception threshold (threshold words), and event-related brain potentials (ERPs) triggered by threshold and above threshold words were analyzed. In the threshold condition, both panic patients and control participants correctly recognized more panic-related than neutral words. An additional analysis restricted to participants who used an intuitive strategy for word identification revealed an enhanced frequency of correctly identified panic-related words in panic patients. In the ERPs, only panic patients exhibited enhanced positive potentials during early time windows (200-400 ms after stimulus presentation) triggered by panic-related compared to neutral threshold words. In late (400-600 ms) and very late (600-1000 ms) time windows, both groups showed a greater ERP positivity for panic-related than for neutral words. These data suggest that panic patients are characterized by an early automatic and elaborated processing of disorder-relevant stimuli.

Adult↗
PubMed2005

Selective processing of pain-related word stimuli in subclinical depression as indicated by event-related brain potentials.

An intense discussion still exists as to whether pain and depression are causally related or independent of each other. To investigate processing of pain-related word stimuli in subclinically depressed individuals, we designed an event-related potentials study in a group control design. Pain words and neutral words were presented to 16 subclinically depressed and 16 control participants. Behavioral and electrophysiological measures were taken during lexical decision and recognition tasks. Depressive compared to control participants showed enhanced P300 amplitudes at parietal electrodes triggered by pain-related words during the lexical decision task, which presumably is a sign of enhanced recollection processes for these word stimuli. In line with these electrophysiological findings, depressed participants also tended to better recall the pain-related words in the later recognition task than control participants. We conclude that subclinically depressed individuals selectively process pain-related stimuli, and this processing bias could enhance their vulnerability to develop pain symptoms.

Adult↗
PubMed2005

Altered processing of pain-related information in patients with fibromyalgia.

Pressure pain thresholds (PPTs) and event-related potentials (ERPs) elicited by emotional words were analyzed in 12 patients with fibromyalgia (FM) and 12 matched healthy subjects. PPTs were assessed at the middle finger of both hands, before and after the experiment. Overall, FM patients and healthy subjects did not differ in PPT. Nevertheless, FM patients as compared with healthy controls were characterized by a significant enhancement of pain sensitivity from the beginning to the end of the experiment indicating a long lasting sensitization due to repeated stimulation. ERPs were recorded during a language decision task where subjects had to react to unpleasant pain-related and emotionally neutral words depending on syntactic or orthographic cues. An emotional category effect was observed on N400 and P300 components of the ERP, indicating that unpleasant words elicited more positive amplitudes than neutral words. A significant group effect was observed on P200 amplitudes, showing reduced amplitudes in FM patients as compared to healthy controls. Furthermore, unpleasant pain-related compared to neutral words triggered significantly enhanced late positive slow waves in healthy controls, while a comparable effect was not found in FM patients. The ERP and PPT data suggest that FM patients are characterized by an altered cognitive processing of pain-related information and by an abnormal adaptation to mechanical pain stimuli, respectively.

Adult↗
PubMed2005

Covariation bias and its physiological correlates in panic disorder patients.

A covariation bias, i.e., the overestimation of random contingencies between fear-relevant stimuli and aversive consequences, seems to characterize anxiety disorders. Panic patients (n=30) and healthy controls (n=25) were exposed to panic-relevant, neutral, and phobia-relevant but panic-irrelevant picture stimuli, followed randomly be aversive consequences (acoustic startle stimuli). While covariation estimates reflected objective contingencies in both groups, only panic patients revealed a more negative Contingent Negative Variation (CNV) to panic-relevant than to phobia-relevant and neutral pictures. For startle reflex, only main effects of picture category were found, indicating that valence effects of picture stimuli were not specifically distorted in panic patients. CNV presumably reflects a biased processing of disorder-relevant stimuli by panic patients, perhaps with the expectation that aversive consequences will follow these stimuli.

Acoustic Stimulation↗
PubMed2005

Implicit and explicit memory processes in panic patients as reflected in behavioral and electrophysiological measures.

Implicit and explicit memory processes for panic-relevant and neutral word stimuli were examined in 16 panic patients and 16 healthy participants matched for sex, age, and education, using behavioral and electrophysiological measures. In the study phase, panic-relevant and neutral words were presented and the level of processing was varied by requiring either shallow (orthographic) or deeper (syntactic) processing. Implicit memory was tested with a lexical decision task, explicit memory with a recognition task. Panic patients and healthy participants did not differ in behavioral (response time) or event-related brain potential (ERP) measures of implicit memory. However, panic patients deviated from healthy participants in the recognition test, an explicit memory test. Although recognition of panic words was overall worse compared to neutral words, panic patients compared to healthy participants exhibited enhanced discrimination scores and faster reaction times for panic words. The level of processing manipulation had comparable effects on patients and healthy participants. While neither behavioral nor electrophysiological measures provided evidence for an implicit memory bias in panic patients, behavioral measures confirmed an explicit memory bias in panic patients for panic-relevant stimuli.

Adult↗
PubMed2004

Modulation of event-related brain potentials during affective picture processing: a complement to startle reflex and skin conductance response?

The present study compared startle response, skin conductance response (SCR) and subjective variables (valence and arousal ratings, viewing time) assessed in an affective picture paradigm with simultaneously registered event-related brain potentials (ERPs) parameters such as P300 and positive slow waves (PSW). Pleasant, neutral and unpleasant pictures from the International Affective Picture System [Lang, P.J., Bradley, M.M., Cuthbert, B.N., 1999. International Affective Picture System (IAPS): Instruction manual and affective ratings. Technical Report A-4, Center for Research in Psychophysiology. University of Florida, Gainesville, Florida] were presented for 8 s, and startle probes were delivered during picture presentation. Startle response was modulated by picture valence, and SCR by picture arousal. ERP positivity was greater for pleasant and unpleasant than for neutral pictures for the P300 amplitude and the positive slow wave (PSW). ERPs showed characteristic differences and a distinct time course for pictures of different valence categories and may deliver useful information not contained in startle response or SCR measures. The simultaneous registration of startle responses and ERPs in the affective picture paradigm seems valuable.

Adult↗
PubMed2002

The Family Questionnaire: development and validation of a new self-report scale for assessing expressed emotion.

The level of expressed emotion (EE) as assessed in the Camberwell Family Interview (CFI) has proved to be one of the best predictors of relapse in schizophrenia. The present study describes the development and validation of the Family Questionnaire (FQ), a brief self-report questionnaire measuring the EE status (criticism, emotional overinvolvement) of relatives of patients with schizophrenia. The FQ classifications in the initial sample of relatives (N=76) correlated significantly with the ratings in the CFI subcategories 'criticism' (78% correct classifications) and 'emotional overinvolvement' (71% correct classifications), as well as with the overall CFI EE ratings (74% correct classifications). A validation study in an independent second sample (N=79) yielded similar results. The overall correct classification rate of 74% remained unchanged. The FQ had better agreement with the CFI on emotional overinvolvement than did other short EE questionnaires.

Adolescent↗
PubMedDate not supplied

Secondary verbal memory: a potential endophenotype of schizophrenia.

This study aimed at identifying neuropsychological endophenotypes of schizophrenia which met the criteria of stability and sensitivity. Twenty-six non-schizophrenic first-degree relatives together with their affected family members (all simplex-families) underwent assessment with a comprehensive neuropsychological test battery both at baseline and 13 months follow-up. Follow-up patients were in a state of stable remission. Further, 21 unrelated, demographically balanced, non-vulnerable controls were tested one at a time. A principal components analysis of our test battery resulted in four factors: (1) Vigilance, attention, and psychomotor, (2) secondary verbal memory, (3) immediate and working memory, and (3) abstraction and problem solving. At baseline testing our study revealed a pattern of selective cognitive deficits in the relative group that is less pronounced, yet qualitatively similar, to that found in the patient sample. The most severe deficits displayed both the patients and their relatives in the secondary verbal memory domain. The dysfunctions in secondary verbal memory at baseline testing significantly correlated with negative symptoms only. Secondary verbal memory deficits proved to be relatively independent of age at onset of illness, illness duration, and neuroleptic dosage. Longitudinally, dysfunctions in the patients' secondary verbal memory fluctuated over time and with negative symptoms, and persisted in remitted patients at the same level as in their relatives. In conclusion, the secondary verbal memory met the criteria of relative stability and sensitivity in our sample of simplex-families. Thus, the secondary verbal memory seems to be a potential endophenotypic marker of schizophrenia, even for cases with a hypothetically lower genetic loading.

Adult↗