Biomedical subjects

A Fallgatter

Publications and source records attributed to A Fallgatter.

3 recordsLinked to original sources

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

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↗

PubMed1996

The predictive value of P300-amplitudes in the course of schizophrenic disorders.

Auditory P300-amplitudes have been found to be correlated with the social functioning and with the impairment in daily life by negative symptoms in cross-sectional studies. In this prospective longitudinal study, the correlation of auditory P300-amplitudes registrated at the index examination was investigated with the clinical outcome after an average of 2.4 years. Based on previous studies, only schizophrenic patients who were in a stabilized residual state were included in the study. Reference-independent P300-parameters of the index examination were correlated with axis V of DSM-III-R (GAF), with the Brief Psychiatric Rating Scale (BPRS) and with the Scale for Assessment of Negative Symptoms (SANS) assessed at the follow-up examination. The correlation of index P300-amplitude with social functioning at follow-up was significant. No correlations of index P300 with the current symptomatology at follow-up, as expressed by BPRS and SANS was found, however. The results indicate a predictive value of the P300-amplitude on the clinical outcome in terms of social functioning of schizophrenic patients.

Acoustic Stimulation↗