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Biomedical subjects

T Brandt

Publications and source records attributed to T Brandt.

At least 271 records · Page 15Linked to original sources
PubMed1976

[Visual stabilization of free stance in infants: a sign of maturity (author's transl)].

The development of the visual contribution to postural stabilization has been tested using a large visual display rotating around the stationary subject's line of sight. This, in the adult, causes a marked optokinetic postural reaction with a shift of the body center of gravity toward the direction of pattern motion. Scalings of the reactions in children between 6 months and 16 years revealed three phases of development: (1) 6--12-month-old-babies show none or very little optokinetic disturbance of their newly acquired ability to sit. With the development of upright stance and gait, optokinetic influences become increasingly important. (2) Children between the age of 2--5 show a marked dependence of postural stability on vision. In them, the disturbing optokinetic stimulus leads to a marked ipsilateral postural deviation or irresistible fall. (3) From 5 to 15 years of age, visual effects on postural balance slowly decrease to their final strength in adulthood--moderate head and body tilt--in response to the rotating stimulus. It is concluded that the optokinetic loop participates rather late in the multisensory process of postural stabilization. The calibration of the three main loops, visual, vestibular, and proprioceptive, seems to be sequential and mutually interactive. Optimal functioning requires the continuous evaluation of the reafferent sensory consequences of self-generated body movements. Optokinetic destabilization of stance requires the maturity of opto-vestibulo-spinal pathways. Its clinical applicability as a maturity test, however, sofar seems limited.

Adolescent↗
PubMed1975

The Aubert-Fleischl phenomenon: a temporal frequency effect on perceived velocity in afferent motion perception.

Apparent velocities of moving visual stimuli are known to be different depending on whether the subject pursues the stimulus (efferently controlled motion perception) or whether the eye is stationary and the image moves across the retina (afferent motion perception). Afferent motion perception of a periodic pattern or a moving single object causes overestimation of velocity (magnitude estimations) as compared to smooth pursuit. This socalled Aubert-Fleischl phenomenon is shown to depend on local temporal frequency stimulation on the retina caused by the repetitive passage of contrast borders of the moving periodic pattern. This is evidenced by the fact that for a given stimulus speed the amount of overestimation is a function of the spatial frequency of the pattern (or the angular subtend of a single moving object) and that the Aubert-Fleischl phenomenon is not observed if a single edge moves. Background characteristics seem not to influence the apparent velocity during smooth pursuit.

Adult↗
PubMed1972

Moving visual scenes influence the apparent direction of gravity.

When an observer views a wide-angled display rotating around his line of sight, he both feels his body tilted and sees a vertical straight edge tilted opposite to the moving stimulus. Displacement of the perceived vertical increases with stimulus speed to reach a maximum (averaging 15 degrees) at 30 degrees per second.

Humans↗