Biomedical subjects

P Scheuerpflug

Publications and source records attributed to P Scheuerpflug.

6 recordsLinked to original sources

PubMed2004

Visual information processing in dyslexic children.

OBJECTIVE: Several studies presented evidence for magnocellular deficits in dyslexics both in behavioural as well as in electrophysiological data of local electrode sites. We investigated two well-known paradigms (motion-onset and random-dot-kinematogram) with regard to global electrophysiological parameters. METHODS: Twenty-one-channel event-related potentials (ERPs) of 16 dyslectic and 15 control children were analyzed with reference-independent methods. For each paradigm quasi stable microstates were identified by means of a data-driven segmentation procedure and compared between both groups. RESULTS: Differences in global ERP responses between dyslexic and control children could be found for rapid moving gratings but not for the dot coherence. CONCLUSIONS: Dyslexic children seem to have some highly specific visual deficits in processing moving stimuli. These deficits can be related to the magnocellular system.

Child↗

PubMed2003

Far field potentials from the brain stem after transcutaneous vagus nerve stimulation.

Recently, the vagus nerve has gained particular interest in neuropsychiatry, as neurodegenerative diseases like Alzheimer's and Parkinson's disease are supposed to affect the brainstem nuclei of the vagus nerve early in their course. In addition, electric stimulation of the vagus nerve has therapeutic effects in otherwise therapy-refractory epilepsies and depressions. So far, no method is available to assess vagus nerve function in this context. On this background and based on the established techniques of early acoustic evoked potentials we investigated if a transcutaneous electric stimulation of the sensory auricular branch of the vagus nerve innervating parts of the outer ear is feasible in healthy subjects using this hypothesis-generated approach. We were able to record a clear, reproducible Vagus Sensory Evoked Potential (VSEP) measured as far field potential probably originating in vagus nuclei in the brainstem. Further studies are needed to test the interindividual stability and test-retest reliability of this new method before potential diagnostic and therapeutic applications might be evaluated.

Adult↗

PubMed2003

Electrophysiological investigation of the effectiveness of methylphenidate in children with and without ADHD.

The Continuous Performance Test (CPT) is an appropriate instrument for assessment of correlates at the brain electrical activity level of attention and response to stimulant medication. The aim of the study was to confirm at the electrophysiological level the clinical effectiveness of methylphenidate (MPH) in children with attention deficit / hyperactivity disorder (ADHD); to this end, a comparative study of hyperactive and healthy control children was undertaken, employing a modified CPT test. Twenty-one channel ERPs from 17 hyperactive boys, with and without MPH treatment, and from 20 healthy control children were analyzed with reference-independent techniques. The resulting quasi-stabile microstates correspond to the time ranges of the conventional ERP components P100, P200 and P300 (with the subcomponents P3a and P3b) and could be discriminated by means of data-based segmentation. The P3a amplitudes of the hyperactive children, in each case with and without MPH medication, were compared with those of healthy controls. P3a segment amplitudes were significantly lower in non-medicated ADHD patients than in healthy children, both following positive and inhibitory stimulus conditions. A significant medication effect was detected following MPH treatment: segment 3 amplitudes in MPH-treated hyperactive children were not significantly different from those of healthy controls. MPH exerts a highly potent effect on stimulus recognition and resulting consequences. Application of the CPT-OX enables the reliable measurement of electrophysiological correlates of the clinical effectiveness of MPH under different stimulus conditions.

Attention↗

PubMed2001

A study of cranial computer tomograms in very early and early onset schizophrenia.

The cranial computer-assisted tomograms of 19 patients suffering from schizophrenic psychoses with onset by age of 14 were examined. The emphasis was on the extent of the inner liquor spaces. Compared to healthy controls, at the beginning of illness a significant enlargement was revealed only in the patient group with very early onset schizophrenia (VEOS, onset prior to the age of 12), whereas children with early onset (EOS, 12 to 14 years of age) showed no significant brain pathology. As a second result, an increase in the extent of the inner liquor spaces seems to correlate with the duration of illness. It is therefore concluded that psychoses interfere with neurodevelopmental processes and cause more severe brain pathology in very young children, already detectable at the onset of the illness. EOS, on the other hand, induces progressive morphological abnormalities over the course of the illness.

Adolescent↗

PubMed2001

Changes of the brain electrical fields during the continuous performance test in attention-deficit hyperactivity disorder-boys depending on methylphenidate medication.

OBJECTIVE: The continuous performance test (CPT) is successfully applied to evaluate attentional performance in attention-deficit hyperactivity disorder (ADHD)-children. The aim of the present study was to investigate the changes of the topographic P300-features in relation to methylphenidate-medication and to different attentional processes in primer- and distractor-conditions. METHODS: Twenty-one-channel-ERPs of 17 ADHD-boys were analyzed with reference-independent methods. Four quasi stable microstates within the time frames of conventional P100, P200, P3a and P3b components were identified by means of a data-driven segmentation procedure. RESULTS: In segment 3 topographical assessment yielded a significant occipital and right-shift of the positive centroid, longer centroid distance and higher amplitudes in primer- than in distractor conditions. MPH increased the amplitude and distance in primer and distractor-condition, without changing the topography. In segment 4 the electric field strength of distractor-conditions collapsed, whereas the primer condition showed a strong fronto-parietally oriented potential-field. There was a tendency to higher amplitudes due to MPH-medication. CONCLUSIONS: These results indicate a robust neurophysiologic differentiation of cognitive processes. MPH activates an early (P3a) covert attention process indicated by increased amplitudes and centroid. No effects were seen in later processes. Based on these effects, we propose to use the amplitude- and distance-increase in microstate 3 as an indicator of MPH efficacy in ADHD-boys.

Adult↗

PubMed2000

Stability of late event-related potentials: topographical descriptors of motor control compared with the P300 amplitude.

The P300-amplitude evoked with an acoustic oddball-paradigm is considered the most stable late event-related potential (ERP). This amplitude-index has become a standard parameter in electrophysiology. Recently, a robust ERP-parameter (NoGo-anteriorization, NGA) has been introduced, which reflects spatial brain electrical changes in relation to execution and inhibition of a motor response elicited with a Continuous Performance Test (CPT). The current study refers to the stability of this new topographical ERP-parameter compared to the stability of the classical P300-amplitude. For that purpose, 12 healthy subjects were investigated with both paradigms during recording of a 21-channel EEG. Analysis of the resulting ERPs revealed a very high stability for both, topographical and amplitude index: In every single subject, the brain electrical fields were characterized by a more anterior location in the NoGo- compared to the Go-condition (=NGA) and by higher amplitudes after target compared to distractor condition. T-tests, analyses of the effect size and of the power revealed equivalent differences between the two contrasting conditions for the topographical compared to the amplitude index. These results indicate that the stability of the topographical ERP-parameters elicited with the CPT is sufficient for an electrophysiological standard-index. The possibility to elicit a robust and specific spatial brain activation with the CPT is an ideal completion to the classical P300 amplitude effect and, therefore, hopefully will be a useful expansion of the standard paradigms in electrophysiological laboratories.

Adult↗