Showing papers by "Gert Pfurtscheller published in 1990"

Topographical display and interpretation of event-related desynchronization during a visual-verbal task.

Abstract: Multichannel EEG recordings were performed during a visual-verbal judgement task with a verbal response using an event-related paradigm. EEG trials of 7 sec were first digitally band pass filtered (10–12 Hz, 10–11 Hz, 11–12 Hz), and the amplitudes were then squared and averaged over all trials. This processing method results in a time course of alpha power and allows us to quantify the event-related desynchronization (ERD) in each EEG channel and to compute series of ERD maps in intervals of 125 msec. Analyzing the 10–11 Hz band, it was possible to study the time course and topographical pattern of cortical activation during visual encoding and cognition. Analysis of the 11–12 Hz band has enabled us, for the first time, to study the time course, spatial localization and extent of activation of speech, premotor and motor areas. We found that the speech centers were activated maximally 250 to 375 msec before speech onset and the SMA about 250 msec before speech onset. The results are preliminary, but demonstrate how much information can be extracted from the scalp EEG.

Electroencephalographic and evoked potential monitoring in the hyperbaric environment

Abstract: The purpose of this study was to investigate brain bioelectrical activity during hyperbaric oxygenation by continuous and simultaneous monitoring of electroenccphalographic and bimodal (auditory, somatosensory) evoked potentials. Multivariable recordings (electroencephalogram, brainstem auditory evoked potentials, early somatosensory evoked potentials, heart rate, heart rate variability, and transcutaneous partial pressure of oxygen) were measured with a new technique in 12 healthy male volunteers 26 to 52 years old (mean ± SD, 35.9 ± 9.5 years). Recordings were obtained while the subjects breathed (1) air at normal atmospheric pressure, (2) 100% oxygen at normal atmospheric pressure, (3) air at 2 atm (10 meters sea water [msw]), and (4) 100% oxygen at 2 atm (10 msw). Spontaneous brain electrical activity, somatosensory evoked potentials, and heart rate variability were not significantly affected during hyperbaric oxygenation, whereas the heart rate showed a significant decrease (pairedt test,P < 0.05). Alterations in brainstem auditory evoked potentials were seen under hyperbaric conditions and did not reach statistical significance (increase of the I-V interpeak latency by pairedt test;P < 0.2). All subjects showed insignificant increases in dominant alpha frequency and decreases in delta frequency under hyperbaric situations.

Multivariables Langzeit-Monitoring von zerebralen und kardiovaskulären Größen mit Hilfe eines Personal-Computers - Multivariable Longterm-Monitoring of Cerebral and Cardiovascular Parameters with the Aid of a Personal Computer

Abstract: Schlüsselwörter: Hirnfunktionsüberwachung, EEG-Leistungsspektren, evozierte Potentiale, Schlafmonitoring, Coma-Monitoring Die gleichzeitige und kontinuierliche Erfassung und Verarbeitung von EEG, evozierten Potentialen, verschiedenen kardiovaskulären und respiratorischen Signalen wurde mittels eines Per. sonal-Computers gesteuerten Meßsystems realisiert. Dieses System findet derzeit bei der Überwachung von kritisch kranken Patienten und bei Schlafuntersuchungen an Säuglingen seine Anwendung.

Ereignisbezogene Desynchronisation und die Wahl des Alpha-Frequenzbandes zur Quantifizierung kortikaler Prä- und Poststimulus-Aktivierung

Abstract: The amount of event-related decrease of increase in alpha-band power is termed "Event-Related Desynchronization" or ERD. In this study, ERD is used as an index of cortical activation, which not only can be applied to monitor poststimulus but prestimulus processes as well. Usually, ERD is analyzed within a fixed range of alpha-frequency, typically within a range of 8-12 Hz. alpha-frequency, however, shows a considerable between subject variation, even in a sample of subjects with comparable age. The purpose of this study, thus is to show as to how the range of alpha-frequency affects the calculation of ERD. Two different methodological approaches were compared. First, ERD was calculated within a fixed range of 8-12 Hz. Second, ERD was calculated within an individual range, which was adjusted to the individually determined alpha-frequency of each subject. A sample of ten right handed subjects participated in an episodic memory experiment, in which target words, shown in a earlier session of the experiment, were to be identified. A time span of 375 ms preceding and following the presentation of a word was defined as the "pre-" and "poststimulus" interval. EEG-signals were recorded unipolarly from 29 leads. The results show a rather localized increase of ERD in the poststimulus interval. In the prestimulus interval on the other hand, the average magnitude of ERD is much lower and the topographical distribution less localized. Most importantly, however, when comparing the two methods of analyzing ERD, those ERD-values calculated within an individually determined alpha-band, are superior in order to differentiate between the pre- and poststimulus interval.

Multimodal evoked potentials and heart rate variability in comatose patients. 3. Electrophysiologic findings in inflammatory diseases of the brain

Abstract: Multimodal evoked potentials and heart-rate variability (HRV) measurements were performed in a total of 15 comatose patients with inflammatory diseases of the brain. The following potentials were recorded: Brainstem auditory evoked potentials (BAEP), early (SSEP) and long latency (SEP) somatosensory evoked potentials and visual evoked potentials (VEP). The results of the initial BAEP recordings indicate that in 83% of the patients the IV-V interpeak latency was prolonged and out of the range of normal values. Additionally an atypical form of the IV-V wave complex was detected. The SSEP after electrical stimulation demonstrated pathological findings in 90% of the patients; long latency components after mechanical vibration could be identified only by 30%. The results of the VEP show an attenuation of vertex VEP (mean value: 43%). Heart-rate variability of the patients was calculated (mean +/- SD) to be 2.5 +/- 1.4% (norm: 7.8 +/- 2.5%) with a mean heart-rate of 95.2 +/- 16.6/min (norm: 67.8 +/- 10.7/min).

BRAINDEX: an interactive, knowledge-based system supporting brain death diagnosis.

Abstract: BRAINDEX (Brain-Death Expert System) is an interactive, knowledge-based expert system offering support to physicians in decision making concerning brain death. The physician is given the possibility of communicating in almost natural language and, therefore, in terms with which he is familiar. This updated version of the system is implemented on an IBM-PC/AT with the expert system shell PC-PLUS and consists of about 430 rules. The determination of brain death is realized with backward chaining and for the optional coma-scaling a forward-chaining mechanism is used.