Biomedical subjects

G Pfurtscheller

Publications and source records attributed to G Pfurtscheller.

231 records · Page 13Linked to original sources

PubMedDate not supplied

Spatiotemporal analysis of alpha frequency components with the ERD technique.

EEG data from 30 channels were recorded during movement and reading tasks and analyzed in the three frequency bands 6- 8 Hz, 8-10 Hz and 10-12 Hz. For each frequency band, the ERD (event-related desynchronization) was quantified and displayed in the form of time courses and maps. The results show that the ERD pattern varies with the frequency component analyzed. In general, upper alpha components (10-12 Hz) demonstrate a short-lasting, task-specific and localized ERD; the ERD of lower alpha components is long-lasting (greater than 1 sec) and widespread. The ERD can be interpreted as a sign of cortical activation, whereby desynchronization of upper alpha components may reflect more task-specific processes, and desynchronization of middle and lower alpha components may be related to the level of expectancy and attention.

Alpha Rhythm↗

PubMedDate not supplied

Respiration and heart rate variation in normal infants during quiet sleep in the first year of life.

Forty-three all-night sleep recordings have been performed on 19 control infants of the ages 6 weeks, 6 months and 1 year. During eight hour periods 22 physiological parameters were sampled by a personal computer based monitoring system and stored on an optical disk. This paper reports on spectral analysis of breathing and heart rate patterns during the first and last episode of quiet sleep at three different age groups. The results demonstrate that the respiratory rate during quiet sleep decreases (6 weeks: 37.2 +/- 5.4; 6 months: 30.1 +/- 4.9; 1 year: 24.1 +/- 1.8; adults (mean age 25.1 +/- 2.8 years; n = 10): 14.8 +/- 1.8; values are means +/- one standard deviation in breaths/min) and the respiratory coefficient Pm/Ps (higher values of Pm/Ps indicate lower respiratory variability) increases with age (6 weeks: 2.3 +/- 0.7; 6 months: 3.2 +/- 1.1; 1 year: 3.4 +/- 1.0; adults: 4.5 +/- 1.0). The calculation of the heart rate in beats per minute (bpm) and heart rate variability (%) revealed the following results: 6 weeks: 127.4 +/- 11.5 bpm, 3.8 +/- 1.5%; 6 months: 119.4 +/- 17.3 bpm, 4.2 +/- 1.7%; 1 year: 110.3 +/- 21.5 bpm, 5.8 +/- 2.3%; adults: 59.2 +/- 8.5 bpm, 4.3 +/- 2.2%. A comparison of the cardiorespiratory data from the first and last quiet sleep period showed no significant differences within either age group.

Cerebral Cortex↗

PubMedDate not supplied

[Acoustically evoked brain stem potentials in infants at risk for SIDS with and without aminophylline therapy].

We investigated brainstem auditory evoked potentials (BAEP) in 20 infants at risk of SIDS (age 5 days to 4 months) and in 7 control infants (age 5 days to 4 months). 19 infants were diagnosed as having sleep apnea syndrome (SAS), which we consider to be a possible risk factor for SIDS. The diagnosis of SAS was made in general in the presence of clinical symptoms such as apneas, cyanosis during sleep, poorly coordinated sucking, swallowing and respiration and gastro-oesophageal reflux in combination with an abnormal pneumogramm in a one hour oxycardiorespirography. One infant had the history of a near miss event but a normal pneumogramm, 2 infants, both with SAS, were siblings of SIDS infants. We applied BAEP on 12 infants at risk of SIDS with and on 12 infants at risk of SIDS without aminophyllin treatment. 3 infants at risk of SIDS had two BAEP studies, one before and one during aminophyllin treatment. The time interval between these two studies was 1 week to 16 days. Aminophyllin, given only to infants with SAS was administered orally (therapeutic range 4-10 micrograms/ml). All infants at risk of SIDS and all control infants had normal I-V-IPL (below 2 x SD). There was a tendency to longer I-V IPL in infants at risk of SIDS. When infants at risk of SIDS with and without aminophyllin treatment were compared as a group the I-V-IPL was shorter in the infants with aminophyllin. BAEP can be useful in studying disturbances of the autonomic function of brainstem centers but do not allow the prediction of an individual SIDS risk.

Aminophylline↗

PubMedDate not supplied

[Braindex--an expert system for the diagnosis of brain death].

An IBM PC-based system was developed as a decision-supporting system for the diagnosis of brain death. Braindex has been realized with the expert system Tool PC-Plus, and includes a knowledge base containing 300 rules organized in 8 frames. Both forward chaining and backward chaining are used in the inference engine. Braindex also includes a text archive and a lexicon. The data of 42 brain death patients are stored in the data bank (300 parameter per patient). The system is presently in the first stage of clinical application.

Brain Death↗

PubMedDate not supplied

[Al-assisted, transputer based EMG system--concept, components and initial results].

An EMG system has been developed capable of doing an EMG analysis as well as providing diagnostic support with the aid of an integrated expert system. The goal of this EMG system is to reduce the time of examination and to increase the reliability of the diagnosis. In order to obtain many parameters from the EMG signal, different analysing methods capable of running in parallel are needed. The system has been realized with a transputer network. Thus it is possible to distribute the software components to different processors with high level of efficiency. For software development we use the operating system Helios. This makes it possible to use the standard I/O environment X-Windows.

Computer Communication Networks↗

PubMedDate not supplied

Realtime measurement of stroke volume--an adaptive monitoring system and its application.

A variety of monitoring systems is available for special fields of clinical application and scientific research. Whenever requirements change data acquisition and handling of signal analysis have to be adapted or even completely new structured, especially in real-time applications. This can be a time consuming procedure. In order to be able to focus on the development of algorithms without taking care how data are acquired a monitoring system has been developed which can be adjusted in terms of signal acquisition, analysis and user handling. New algorithms can be added and polygraphical presentation of results can be adjusted for special clinical requirements. As a specific application the online and real time calculation left ventricular ejection time (LVEJT), stroke volume (SV), cardiac output (CO), mean blood pressure and total peripheral resistance (TPRI) is presented.

Algorithms↗

PubMedDate not supplied

[Elimination of respiratory effects on motion-induced changes in heart rate].

As part of a comprehensive movement study, the cardiac response induced by voluntary movement of the right and left index fingers was analysed. Since subjects synchronised movement and respiration, a special method that permitted the differentiation of movement-induced from respiratory-related effects was employed. This method is described, and its advantages over the standard method of estimating stimulus-induced cardiac responses are discussed. The results obtained in three subjects are presented, and the impact of the synchronisation of movement and respiration on the induced cardiac response demonstrated.

Artifacts↗

PubMedDate not supplied

Design of an EEG-based brain-computer interface (BCI) from standard components running in real-time under Windows.

An EEG-based brain-computer interface (BCI) is a direct connection between the human brain and the computer. Such a communication system is needed by patients with severe motor impairments (e.g. late stage of Amyotrophic Lateral Sclerosis) and has to operate in real-time. This paper describes the selection of the appropriate components to construct such a BCI and focuses also on the selection of a suitable programming language and operating system. The multichannel system runs under Windows 95, equipped with a real-time Kernel expansion to obtain reasonable real-time operations on a standard PC. Matlab controls the data acquisition and the presentation of the experimental paradigm, while Simulink is used to calculate the recursive least square (RLS) algorithm that describes the current state of the EEG in real-time. First results of the new low-cost BCI show that the accuracy of differentiating imagination of left and right hand movement is around 95%.

Amyotrophic Lateral Sclerosis↗

PubMedDate not supplied

Source localization of induced cortical oscillations during tactile finger stimulation.

We investigated the EEG beta event-related synchronization (ERS) after tactile finger stimulation in three subjects. Prior studies from our group using electrical stimulation and self-paced movement showed a beta rebound within one second after stimulation respectively movement offset. As the tactile-stimulation-data showed a similar ERS behaviour, we extracted the cortical sources for this beta rebound by the linear estimation method in order to see whether the representation areas of different fingers were distinguishable (as is possible with MEG data). Although realistic head models of two subjects were used for the calculations the fingers could not be spatially distinguished. However, regarding the whole spatio-temporal pattern of the ERS for different fingers clear differences can be observed.

Adult↗

PubMedDate not supplied

"Resonance-like" frequencies of sensorimotor areas evoked by repetitive tactile stimulation.

The aim of the present study was to investigate resonance-like frequencies of somatosensory steady-state evoked potentials (SSSEPs) during mechanical stimulation of the left and right index finger. The resonance effects were studied in a group of normal subjects at 8 frequencies between 17 Hz and 31 Hz. Band power was computed in 2 s epochs in eight 2 Hz beta bands starting from 16-18 Hz up to 30-32 Hz and referred to a baseline prior to stimulation. For each subject the band with the largest band power increase was determined on electrodes overlying the contralateral hand area. The band power maxima and therewith the "resonance-like" frequencies were found around 27 Hz.

Adolescent↗

PubMedDate not supplied

Estimating the mutual information of an EEG-based Brain-Computer Interface.

An EEG-based Brain-Computer Interface (BCI) could be used as an additional communication channel between human thoughts and the environment. The efficacy of such a BCI depends mainly on the transmitted information rate. Shannon's communication theory was used to quantify the information rate of BCI data. For this purpose, experimental EEG data from four BCI experiments was analyzed off-line. Subjects imaginated left and right hand movements during EEG recording from the sensorimotor area. Adaptive autoregressive (AAR) parameters were used as features of single trial EEG and classified with linear discriminant analysis. The intra-trial variation as well as the inter-trial variability, the signal-to-noise ratio, the entropy of information, and the information rate were estimated. The entropy difference was used as a measure of the separability of two classes of EEG patterns.

Attention↗

PubMedDate not supplied

Frequency component selection for an ECoG-based brain-computer interface.

The aim of the present study was to investigate the most significant frequency components in electrocorticogram (ECoG) recordings in order to operate a brain computer interface (BCI). For this purpose the time-frequency ERD/ERS map and the distinction sensitive learning vector quantization (DSLVQ) are applied to ECoG from three subjects, recorded during a self-paced finger movement. The results show that the ERD/ERS pattern found in ECoG generally matches the ERD/ERS pattern found in EEG recordings, but has an increased prevalence of frequency components in the beta range.

Brain Mapping↗

PubMedDate not supplied

EEG mapping: current status and future prospects.

EEG mapping is the topographical display of parameters evaluated from multichannel EEG recordings. Different problems connected with EEG mapping are: number of electrodes, interpolation between electrodes, types of reference and statistical treatment of maps. These problems are discussed briefly and examples are given. To complete this report, a short historical background along with some comments about the clinical settings have been provided and attention given to future prospects.

Brain Mapping↗

PubMedDate not supplied

Quantification of autonomic activity in the brainstem in normal, comatose and brain dead subjects using heart rate variability.

The heart rate variability is defined as variation in distance between sequential ventricular complexes in the electrocardiogram and can be given in percent by referring the standard deviation to the average values of heart rate. The bivariate distribution of heart rate variability and of heart rate shows a discrimination of the group of comatose patients from brain dead subjects and normals.

Adolescent↗

PubMedDate not supplied

EEG-based brain computer interface (BCI). Search for optimal electrode positions and frequency components.

Several laboratories around the world have recently started to investigate EEG-based brain computer interface (BCI) systems in order to create a new communication channel for subjects with severe motor impairments. The present paper describes an initial evaluation of 64-channel EEG data recorded while subjects used one EEG channel over the left sensorimotor area to control on-line vertical cursor movement. Targets were given at the top or bottom of a computer screen. Data from 3 subjects in the early stages of training were analyzed by calculating band power time courses and maps for top and bottom targets separately. In addition, the Distinction Sensitive Learning Vector Quantizer (DSLVQ) was applied to single-trial EEG data. It was found that for each subject there exist optimal electrode positions and frequency components for on-line EEG-based cursor control.

Adult↗