Renkl A. E. H., Heinrich S. P., Bach M.

Universitäts-Augenklinik, Killianstr. 5, 79106 Freiburg

Objective: Visual motion perception is as relevant as brightness- or colour perception, but rarely examined. Visual evoked potentials could help to examine human motion perception, but which stimuli are suited best to specifically activate motion detecting neurons?
Methods: Motion detectors are characterized by their directional specificity which in turn can be detected via motion adaptation. In 10 subjects we compared 3 different moving test patterns: vertical sinusoidal gratings, vertical random bars and random dots. A baseline condition was recorded to brief, non-adapting test movements to the left and to the right (8°/s). Then after continuous rightwards motion the motion system is unidirectionally adapted and the responses to brief right- and leftwards motion compared. Further we tested for cross-adaptation effects.
Results: All three stimuli evoked clear motion responses. The degree of unidirectional adaptation varied: random dots showed the strongest directionality, and sinusoids the least. Cross adaptation (e.g. adapting do random dot movement, testing sinusoids) always had less adaptation effect than within-stimulus adaptation (p<0.01).
Conclusion: A motion-onset stimulus activates motion detectors but also many motion-unspecific mechanisms. Different motion stimuli activate different subpopulations of detectors; random-dot motion appears to activate the largest population. Grating stimuli (sinusoidal or random bars) appear ill-suited to examine motion perception.

Copyright © Deutsche Ophthalmologische Gesellschaft, 2001. All rights reserved.

Last updated: 

Webdesign: SPALLEK.COM