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W Strik

Publications and source records attributed to W Strik.

12 recordsLinked to original sources
PubMed2006

Sex differences in semantic processing: event-related brain potentials distinguish between lower and higher order semantic analysis during word reading.

Behavioral studies suggest that women and men differ in the strategic elaboration of verbally encoded information especially in the absence of external task demand. However, measuring such covert processing requires other than behavioral data. The present study used event-related potentials to compare sexes in lower and higher order semantic processing during the passive reading of semantically related and unrelated word pairs. Women and men showed the same early context effect in the P1-N1 transition period. This finding indicates that the initial lexical-semantic access is similar in men and women. In contrast, sexes differed in higher order semantic processing. Women showed an earlier and longer lasting context effect in the N400 accompanied by larger signal strength in temporal networks similarly recruited by men and women. The results suggest that women spontaneously conduct a deeper semantic analysis. This leads to faster processing of related words in the active neural networks as reflected in a shorter stability of the N400 map in women. Taken together, the findings demonstrate that there is a selective sex difference in the controlled semantic analysis during passive word reading that is not reflected in different functional organization but in the depth of processing.

Adult↗
PubMed2006

Plasticity in the adult language system: a longitudinal electrophysiological study on second language learning.

Event-related potentials (ERPs) were used to trace changes in brain activity related to progress in second language learning. Twelve English-speaking exchange students learning German in Switzerland were recruited. ERPs to visually presented single words from the subjects' native language (English), second language (German) and an unknown language (Romansh) were measured before (day 1) and after (day 2) 5 months of intense German language learning. When comparing ERPs to German words from day 1 and day 2, we found topographic differences between 396 and 540 ms. These differences could be interpreted as a latency shift indicating faster processing of German words on day 2. Source analysis indicated that the topographic differences were accounted for by shorter activation of left inferior frontal gyrus (IFG) on day 2. In ERPs to English words, we found Global Field Power differences between 472 and 644 ms. This may due to memory traces related to English words being less easily activated on day 2. Alternatively, it might reflect the fact that--with German words becoming familiar on day 2--English words loose their oddball character and thus produce a weaker P300-like effect on day 2. In ERPs to Romansh words, no differences were observed. Our results reflect plasticity in the neuronal networks underlying second language acquisition. They indicate that with a higher level of second language proficiency, second language word processing is faster and requires shorter frontal activation. Thus, our results suggest that the reduced IFG activation found in previous fMRI studies might not reflect a generally lower activation but rather a shorter duration of activity.

Adult↗
PubMed2004

Subsecond changes of global brain state in illusory multistable motion perception.

This study explored transient changes in EEG microstates and spatial Omega complexity associated with changes in multistable perception. 21-channel EEG was recorded from 13 healthy subjects viewing an alternating dot pattern that induced illusory motion with ambiguous direction. Baseline epochs with stable motion direction were compared to epochs immediately preceding stimuli that were perceived with changed motion direction ('reference stimuli'). About 750 ms before reference stimuli, Omega complexity decreased as compared to baseline, and two of four classes of EEG microstates changed their probability of occurrence. About 300 ms before reference stimuli, Omega complexity increased and the previous deviations of EEG microstates were reversed. Given earlier results on Omega complexity and microstates, these sub-second EEG changes might parallel longer-lasting fluctuations in vigilance. Assumedly, the discontinuities of illusory motion thus occur during sub-second dips in arousal, and the following reconstruction of the illusion coincides with a state of relative over-arousal.

Adult↗
PubMed2003

Functional imbalance of visual pathways indicates alternative face processing strategies in autism.

OBJECTIVE: To investigate whether autistic subjects show a different pattern of neural activity than healthy individuals during processing of faces and complex patterns. METHODS: Blood oxygen level-dependent (BOLD) signal changes accompanying visual processing of faces and complex patterns were analyzed in an autistic group (n = 7; 25.3 [6.9] years) and a control group (n = 7; 27.7 [7.8] years). RESULTS: Compared with unaffected subjects, autistic subjects demonstrated lower BOLD signals in the fusiform gyrus, most prominently during face processing, and higher signals in the more object-related medial occipital gyrus. Further signal increases in autistic subjects vs controls were found in regions highly important for visual search: the superior parietal lobule and the medial frontal gyrus, where the frontal eye fields are located. CONCLUSIONS: The cortical activation pattern during face processing indicates deficits in the face-specific regions, with higher activations in regions involved in visual search. These findings reflect different strategies for visual processing, supporting models that propose a predisposition to local rather than global modes of information processing in autism.

Adolescent↗
PubMed1997

Increased duration and altered topography of EEG microstates during cognitive tasks in chronic schizophrenia.

The surface EEGs of 32 medicated chronic schizophrenic patients, 12 unmedicated chronic schizophrenics and 35 matched healthy controls were analyzed by adaptive segmentation of continuous EEG during a rest condition, a mental arithmetic task, and a CNV paradigm. Results indicate increased duration of brain microstates in both unmedicated and medicated schizophrenics as well as reduced topographic variability. These findings did not vary across the different tasks. Comparing different cognitive tasks, schizophrenics and controls alike showed task-related changes of electric field topography, of EEG microstate duration and of the number of very short microstates (single-peak segments). However, the topography of the microstates during the tasks differed significantly in both medicated and unmedicated schizophenics from that of controls. Age, sex and educational levels did not influence these findings. Neuroleptic medication correlated negatively with microstate duration in a dose-dependent way. There was an inverse relationship between topographic variability and negative symptoms as well as BPRS scores. It is concluded that the temporo-spatial characteristics of brain electric activity indicate an impoverished array of functional modes and enhanced stability of brain electrical microstates in schizophrenia.

Adult↗
PubMed1992

[Status of amine hypotheses in depressive disorders].

The biochemical effects of drugs modulating mood are the basis for still relevant hypotheses relating depressive disorders to dysfunctions of noradrenergic, serotonergic and/or cholinergic neurotransmission. The time course as well as the dose-effect-relationships point to the relevance for mood elevation of secondary adaptive processes rather than the direct actions of antidepressants. Direct evidence of dysfunctions sufficiently explaining the actual illness of the single individual has not been obtained at the level of transmitters, metabolites and receptors. Deficits of serotonergic transmission seem to be related to a personality dimension of poor impulse control closer than to nosological categories. This dimensional concept might also be valid for the relationships between cholinergic sensitivity and stress tolerance. Depression itself is possibly due to imbalances of multiple neuronal systems.

Acetylcholine↗
PubMed1970

[Fat embolism].

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Adult↗
PubMedDate not supplied

[Schizophrenia, manic-depressive psychoses and "middle cases". A clinical and nosologic study with cluster analysis].

Having analyzed the main nosographies concerning the endogenous psychoses problem, the A. aim at obtaining a subdivision of the psychotic patients into classes based on the similarity shown by the same patients about symptoms found out by a transverse examination. For this purpose, 246 psychotic inpatients have been given PSE to evaluate the presence/absence of 18 symptoms considered discriminant to the clinical rating of the patients. Such data have been processed by a Cluster Analysis. We got 7 groups of probands that have stressed the relevant number of cases with a mixture of affective and schizophrenic symptoms. We suggest the use of a bidimensional model to get a proper fitting of psychotics with mixed symptomatology.

Adolescent↗