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Biomedical subjects

G van den Brink

Publications and source records attributed to G van den Brink.

At least 19 recordsLinked to original sources
PubMed1986

A model for the slow control system during monocular fixation.

A method has been developed to compare the behaviour of the oculomotor control system during steady fixation and during reactions on small stimulus movements. No difference between the two conditions was found, and the reactions on small steps (1-5') and step/ramps (2-10'/sec), during normal and stabilized vision, have been used to develop a model for the slow control system during fixation. The model consists of a position channel, which integrates the retinal error, and a velocity channel, that uses both the retinal velocity and an efferent copy of the eye velocity. The model parameters have been estimated from the data of four subjects.

Eye Movements↗
PubMed1982

The effect of presentation time on detection and diplopia thresholds for vertical disparities.

Detection and diplopia thresholds for vertical disparities are found to decrease when the presentation time of the stimulus with disparity is increased between 20 msec and 2 sec. This result supports the following notions previously put forward in literature; (a) the human visual system embodies detection processes which reveal vertical disparities; there is no sensory fusion mechanism in this system that gradually conceals vertical disparities: (b) the detection of vertical disparity in tachistoscopically presented stimuli is not based upon the initial appearance of the stimulus with disparity.

Depth Perception↗
PubMed1982

Detection of vertical disparties.

Psychometric curves determined for the detection of differences between vertical disparities as a function of the reference disparity for three presentation times (20 msec, 160 msec and 2 sec) and for two eccentricites of the stimulus (0.5 degree and 4 degrees) are presented. The results show that the detectability of disparity differences first increases and then decreases when the reference disparity is increased from zero. It further appears that the only effect of the stimulus presentation time and eccentricity on the psychometric curves and their dependency on the reference disparity is that the effective disparities observed are multiplied by a constant factor. The experimental data can be described by a signal detection model with two special features around zero disparity where binocular single vision occurs, viz. Loss of information about the sign of disparity and presence of intrinsic noise at a level up to 25% higher than the minimum level found at intermediate disparities.

Differential Threshold↗
PubMed1982

On the relativity of pitch.

The way we interpret a given set of sensory stimuli can depend very strongly on our choice of cues. The resulting ambiguity is particularly familiar in visual perception, and underlies many well-known visual illusions. It is shown that comparable ambiguities exist in the field of hearing, particularly pitch perception.

Auditory Pathways↗
PubMed1980

One and three doses of propranolol a day in hypertension.

In 26 patients with essential hypertension who were on continuous chlorthalidone therapy, 1 and 3 daily doses of propranolol were compared in a crossover study. Plasma propranolol levels and heart rates had larger daily fluctuations on single-dose therapy than on 3 times daily; plasma renin activity was more constant. There was no significant difference in blood pressures. Once-daily propranolol dosage was well tolerated and possibly gave less rise to the troublesome side effect of vivid dreaming.

Adolescent↗