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Updated: Aug 9, 2026
Eye Movement Monitoring of Memory
Published on: August 15, 2010
Eye movements and the motion aftereffect: alternatives to the induced motion hypothesis
1Salk Institute for Biological Studies, San Diego, CA 92186-5800.
Abstract:
It has been previously reported that prolonged unidirectional smooth pursuit often produces a negative motion aftereffect (MAE). This was believed to be caused by retinal image motion of stationary environmental contours during pursuit which subsequently produced a primary motion aftereffect in the tracking direction. The peripheral MAE then induced motion in the stationary tracking target resulting in illusory movement in the opposite direction. We have found that a negative MAE is also produced when the adapting field is devoid of any contours. Furthermore, the presence of a moving textured background in conjunction with smooth pursuit produced an MAE whose direction was inconsistent with the induced motion hypothesis. Since all examples of motion aftereffects in this study were associated with the pursuit aspect of the experiment rather than any interactions with background contours, it was proposed that the illusory motion had an oculomotor determinant. A scheme was tentatively outlined in which fixation suppression of an unregistered ocular drift following prolonged pursuit adaptation (pursuit after-nystagmus) produced the post-adaptive motion illusions.
Insights
Prolonged smooth pursuit eye movements can cause motion aftereffects even without visual contours. This suggests oculomotor factors, not just retinal image motion, drive these illusions.
Area of Science:
- Neuroscience
- Vision Science
- Oculomotor Research
Background:
- Prolonged unidirectional smooth pursuit eye movements are known to induce motion aftereffects (MAE).
- Previously, MAE was attributed to retinal image motion of stationary contours during pursuit, leading to illusory motion in the opposite direction.
- This induced motion hypothesis suggested peripheral MAE influenced the central tracking target.
Purpose of the Study:
- To investigate the role of visual contours in smooth pursuit-induced MAE.
- To explore alternative explanations for MAE beyond retinal image motion interactions.
- To determine if oculomotor factors contribute to post-pursuit motion illusions.
Main Methods:
- Adapting the visual field with and without contours during smooth pursuit eye movements.
- Observing MAE direction with and without textured backgrounds during pursuit.
- Analyzing the relationship between pursuit adaptation and subsequent illusory motion.
Main Results:
- A negative MAE was observed even when the adapting field lacked contours.
- A moving textured background did not consistently predict MAE direction during pursuit.
- MAE direction was consistently linked to the pursuit eye movement itself, not background interactions.
Conclusions:
- The induced motion hypothesis is insufficient to explain all smooth pursuit-induced MAE.
- Oculomotor determinants, specifically fixation suppression of ocular drift post-pursuit, are proposed as the cause of these illusions.
- Illusory motion following smooth pursuit adaptation may originate from the oculomotor system itself.
