[Post-traumatic stress disorder in Germany. Results of a nationwide epidemiological study]. / Posttraumatische Belastungsstörungen in Deutschland. Ergebnisse einer gesamtdeutschen epidemiologischen Untersuchung.

In a representative epidemiological study (n=2426) with a broad age range of respondents (14-93 years), prevalence rates of traumatic life events, post-traumatic stress disorder (PTSD), and partial PTSD were estimated. A standardized interview using the trauma checklist of the Composite International Diagnostic Interview and a DSM-IV PTSD symptom checklist (Modified PTSD Symptom Scale) were applied. One-month prevalence rates were 2.3% for DSM-IV PTSD and 2.7% for partial PTSD. There were no gender differences but age-group differences did appear: among persons older than 60, the prevalence of PTSD was 3.4%, whereas the prevalence was estimated at 1.3% among persons aged 14-29 years and 1.9% among those aged 30-59 years. Partial PTSD exhibited the same age distribution, with 3.8% in the elderly, 2.4% in the middle-aged, and 1.3% in young adults. The results correspond with those of other international studies taking war-related consequences for older age groups into account. Our representative study provides the first evidence of higher PTSD prevalence rates among older age groups in the German population, which is assumed to be related to consequences of World War II.

A double-dissociation of English past-tense production revealed by event-related potentials and low-resolution electromagnetic tomography (LORETA).

OBJECTIVES: Evidence of systematic double-dissociations of neural activity associated with the generation of regular and irregular past tense in healthy individuals may prove decisive in distinguishing between single- and dual-route models of morphological processing, because the former (connectionist models of morphological processing) have only been able to simulate double-dissociations of past-tense morphology as low-probability phenomena. METHODS: Twenty-eight channel event-related potentials (ERPs) were recorded in response to past-tense production and subsequently analyzed using a 3-stage strategy. RESULTS: A data-driven algorithm temporally segmented the ERPs into 16 distinct epochs of stable field configuration (microstates). A space-oriented brain electric field analysis determined that one of those epochs, 288-321 ms after the verb stem presentation, showed significant differences between the regular and irregular verb conditions. As a further test of these results, a novel source localization technique that computes 3-dimensional distribution of cortical current density in the Talairach brain atlas--low-resolution electromagnetic tomography--found in the above microstate more activity for regulars in the right prefrontal and right temporal areas and for irregulars in the left temporal areas and the anterior cingulate cortex, which can be taken as evidence of systematic double-dissociation. CONCLUSIONS: The present results achieved with a source localization technique provide evidence of a two-way compartmentalization of neural activity corresponding to regular and irregular past tense, thus corroborating the dual-mechanism character of verb morphology.

Mapping dissociations in verb morphology.

Substantial behavioural and neuropsychological evidence has been amassed to support the dual-route model of morphological processing, which distinguishes between a rule-based system for regular items (walk-walked, call-called) and an associative system for the irregular items (go-went). Some neural-network models attempt to explain the neuropsychological and brain-mapping dissociations in terms of single-system associative processing. We show that there are problems in the accounts of homogeneous networks in the light of recent brain-mapping evidence of systematic double-dissociation. We also examine the superior capabilities of more internally differentiated connectionist models, which, under certain conditions, display systematic double-dissociations. It appears that the more differentiation models show, the more easily they account for dissociation patterns, yet without implementing symbolic computations.

Differences in working memory involvement in analytical and creative tasks: an ERP study.

If, as suggested, creative (insight) problem solving is less systematic and employs less planning than analytical problem solving, the former requires substantially less working memory (WM) than the latter. Subjects simultaneously solved problems and counted auditory stimuli (concurrent WM task), in response to which ERPs were recorded. Counting disrupted analytical, but not creative performance. Peak and time-window average P300 were more frontal during analytical problem solving as compared to insight or counting tones only (control). A PCA extracted two factors in the P3 range, one frontal and one broad left-lateralized, which distinguished analytical from creative problem solving. The findings indicate distinct processing pathways for the two types of tasks with more WM involvement in analytical tasks.