Biomedical subjects

W Röske

Publications and source records attributed to W Röske.

5 recordsLinked to original sources

PubMed1991

[Pattern recognition techniques in sleep polygraphy].

The evaluation of EEG-patterns is usually accomplished by visual analysis. Nowadays however, even personal computers are fast enough for an efficient pattern recognition of EEG signals. Using sleep spindles and K-complexes as examples, our aim was to demonstrate how patterns can be detected in an EEG signal with a high degree of accuracy. Furthermore, recognition of K-complexes has been improved by applying an additional "adaptive algorithm" allowing individual adjustments to the signal's form and amplitude.

Algorithms↗

PubMed1991

[Techniques of determining saccadic parameters].

For the analysis of saccadic eye movements two values were to be computed: the latency of the reaction and the maximum velocity reached by the eye finding the new visual point. The waveform is disturbed especially by noise. With this method, the impurity level can be reduced nearly completely without destroying the curve shape of the saccade.

Fourier Analysis↗

PubMed1990

[A direct current amplifier for measuring eye saccades].

For testing saccadic eye movements three methods are used today: the coil-, the infrared- and the electrode-method. All of these techniques are endowed with advantages and disadvantages. The electrode-method that uses the dipole-character of the eye needs a DC-amplifier with small noise and drift error. The amplifier described here complies with these requirements. It has been used for a long time and disapproves the general opinion that the coil- and the infrared-method are the more expensive but in all cases the better methods.

Amplifiers, Electronic↗

PubMed1989

[Visual motor coordination of AIDS patients, HIV-positive asymptomatic probands and healthy persons during video-tracking].

Here we investigated the applicability of a computer-aided video-tracking as a method for evaluating potential deficits of neural information processing in patients with AIDS and those showing only positive HIV-seroreactivity. Video-tracking was accompanied with a simultaneous recording of EEG. Eight HIV-positive asymptomatic volunteers and eight AIDS-patients with cerebral manifestation of the disease participated in the pilot study. Two groups of eight normals each served as a control. Video-tracking performance of the HIV-positive volunteers and AIDS-patients significantly differed (p less than 0.05) from those of the healthy volunteers. Although the AIDS-patients' performance tended to be worse than that of the HIV-group, this difference was not significant. Power spectrum analysis of the EEG-data indicated that the diminished performance of the two test groups (AIDS and HIV-positives), accompanied by an increased spectral power across the entire frequency range measured in the study, could be an expression of an enhanced synchronization in cortical neuronal networks. The synchronization in turn could be a sign of possible organic brain damage resulting from HIV-infection. In conclusion, we suppose that video-tracking measures parameters which may indicate early deficits of information processing in CNS.

Acquired Immunodeficiency Syndrome↗

PubMed1988

[Estimation of the required bandwidth of a DC amplifier for measurement of eye saccades].

Saccadic eye movements are analysed with DC-amplifiers when electrodes are used. The present investigation on measuring the velocity of eye movement gives an estimation for the required bandwidth, because the upper frequency has a decisive influence on the result. Theoretically there would be no error of measurement if no filters were used. But there are two reasons for filtering. One is that the Shannon-Theorem asks for a limited frequency in order to digitize the signal on a computer later on. The other is an increasing of disturbance in the signal by an extended top frequency. It takes no trouble to solve the first problem by changing the sampling-rate of the computer. The second problem asks for a compromise. Error in measurement will increase by reducing the top frequency, but also disturbances in the signal will be reduced. The value in question of this investigation is the velocity of eye movement, i.e. the maximum gradient in the signal and that could be the gradient of a disturbance-spike. The present estimation shows that an amplifier with two RC-Filters and a Butterworth-Filter second order with a resulting top frequency at 20 Hz (3 dB-limit) offers a good compromise.

Amplifiers, Electronic↗