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Judging relative positions across saccades.
E Brenner1, W J Meijer, F W Cornelissen
1Department of Neuroscience, Erasmus Medical Centre, P.O. Box 1738, Dr. Molenwaterplein 50, 3000 DR Rotterdam, The Netherlands. e.brenner@erasmusmc.nl
Vision Research
|March 23, 2005
Summary
Perceived visual separation depends on retinal image, not eye movements during saccades. Even with intervening eye movements, targets flashed briefly are judged based on their position on the retina.
Area of Science:
- Cognitive Neuroscience
- Visual Perception
- Ophthalmology
Background:
- During smooth pursuit eye movements, the retinal image typically dictates perceived shape, as if parts belong to the pursued object.
- Saccadic eye movements shift gaze between objects, and typically do not involve perception of movement with the eyes.
Purpose of the Study:
- To investigate how individuals perceive the spatial separation between two targets presented sequentially before and after a saccade.
- To determine the influence of retinal separation versus intervening eye movements on perceived target separation.
Main Methods:
- Participants tracked a moving dot while targets were flashed at specific retinal positions with varying intervals (67–242 ms).
- Trials with complete saccades between target presentations were selected for analysis.
- Subjects reported their perceived locations of the flashed targets after each trial.
Main Results:
- For short inter-target intervals, perceived separation was primarily determined by retinal separation, overriding visual references.
- Even with longer intervals, perceived separation only partially incorporated the change in eye orientation.
- Findings were not explained by individual target mislocalization or spatial compression effects near saccades.
Conclusions:
- Retinal separation is the dominant factor in perceived separation for targets presented with short intervals, regardless of intervening saccadic eye movements.
- The visual system prioritizes retinal information for spatial judgments under these conditions, challenging simpler explanations.