Biomedical subjects

W Haustein

Publications and source records attributed to W Haustein.

4 recordsLinked to original sources

PubMed1992

Head-centric visual localization with lateral body tilt.

The aim of the present investigation was to decide whether subjects can correctly judge the head-centric orientation of a display in the dark in spite of the counterrolling of their eyes caused by head tilt. Four subjects were asked to set two luminous points orthogonally to the median plane of their heads, with head and body upright or tilted 90 degrees to the left or right side. The luminous points could be rotated in a frontal plane about a stationary fixation light situated straight ahead. Subjects viewed this display monocularly with either eye. In the same three body positions, ocular counterroll was determined photographically. The settings turned out to be neither accurately oculocentric nor head-centric, and there were considerable inter- and intrapersonal variances. However, on average, display adjustments were more head-centric: mean difference of ocular counterroll between left-ear-down and right-ear-down conditions was 13.2 deg, whereas the mean difference of the subjective head-centric orientations was only 3.8 deg.

Female↗

PubMed1990

Evaluation of retinal orientation and gaze direction in the perception of the vertical.

The orientation of the median plane of the eye with respect to the head varies with gaze direction according to Listing's Law. The subjective vertical (SV), however, is known to be only partially affected by these involuntary variations of eye orientation. In order to learn more about the compensatory process underlying this finding, six normal-sighted young subjects were tested monocularly and binocularly in eight directions of gaze. The results show that: (1) the SVs, determined monocularly for both eyes, fall on corresponding retinal meridians, the binocular SV-settings generally lie between the monocular ones; (2) the tilt of the SV is not linearly related to the tilt angle of the median plane of the eye, as hitherto assumed. On theoretical considerations, the dependence of ocular tilt on gaze direction may be decomposed into three components, which are all treated differently in the compensation process. We interpret these results in the following way: the SV is determined from the sensorially fused image of both eyes and the tilts of the eyes are accounted for by an extra-retinal signal which is common to both eyes. The characteristics of the compensation mechanism may be explained by an extra-retinal signal which relies on information about gaze direction and Listing's Law. Such a signal might be derived from an efference copy of gaze direction commands.

Eye Movements↗

PubMed1989

Considerations on Listing's Law and the primary position by means of a matrix description of eye position control.

Voluntary gaze control obeys the law of Listing. This law specifies the torsion of the eye in every direction of gaze, when the so-called "primary position" of the eye is known. In the present article, some interesting relations between Listing's Law and the primary position on the one hand, and eye muscle innervation on the other hand are derived. A new vectorial description of eye position is introduced which permits to represent Listing's Law by a very simple equation. It also allows to approximate the transformation between eye muscle innervation and eye position by a 3 x 3-matrix in a large field of gaze and with quantities of innervation which are directly related to motoneuron firing rates. It is shown that these innervation quantities must be linearly coupled to yield Listing's Law and that the parameters of this coupling determine the primary position. Finally, relations between innervations and eye muscle forces are considered, and a hypothesis concerning the cooperation of voluntary gaze control and otolith or vergence inputs is presented.

Eye Movements↗

PubMed1986

Automatic analysis overcomes limitations of sleep stage scoring.

A computer programme for the automatic analysis of the sleep EEG and EMG is presented. An EEG parameter is derived which is based on the joint frequency-amplitude distribution of the EEG activity. This newly developed parameter stresses the dynamic development of sleep, composed of alternating phases of EEG synchronization and desynchronization. While synchronization develops slowly, the opposite phase of EEG activity, desynchronization, is more rapid. A particular advantage of the EEG parameter is its continuous scale which results in high resolution. Thus, the parameter reflects gradual EEG changes which a visual analyser would have to classify into the same sleep stage. In addition to the EEG, the EMG is analysed and two parameters are extracted, representing the mean muscle tone and transient EMG activation, respectively. There is a close temporal relationship between the EEG and the EMG with a maximum of transient EMG activity during the phase of EEG desynchronization. The properties of the automatic analysis were compared to the visual analysis on a sample of 12 all-night sleep records. The results show that the EEG parameter also agrees sufficiently with the traditional sleep scoring method and therefore is a valid descriptor of the time course of sleep.

Electroencephalography↗