Visual stability through habituation to sensorimotor contingencies

• Applicant: Professor Dr. Eckart Zimmermann
• Subject Area: Biological Psychology and Cognitive Neuroscience
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 554022301

Although our visual receptors are permanently shifted when our eyes move, we perceive our environment as stable. Maintaining visual stability is particularly challenging when performing saccades, sudden jumps of the eye-ball, which displace the retina with high speed. We have recently proposed the theory of habituation to intra-saccadic stimulation. In this view, during saccades, the brain responds less vigorously to stimuli that reoccur predictably. Visual stability would be the consequence of the brain silencing the neuronal response to the expected visual motion. 
The grant proposal describes four experiments which shall test the theory of habituation against competing theories. These comprise the theory of saccade suppression, which assumes a transient shut-down of the magnocellular pathway during saccade execution and the theory of trans-saccadic masking, which states that the post-saccadic visual input masks the intra-saccadic visual motion. The aim of Experiment 1 is to demonstrate that predictions about visual stimulation in an upcoming saccade determine whether intra-saccadic stimulation is perceived as stationary or not. By repeatedly presenting a certain visual motion speed during a given saccade vector, habituation should also be observable for artificial intra-saccadic motion. Experiment 2 shall investigate the generality of habituation. Will every predictable stimulus become silenced during saccade execution or is habituation specific to visual motion? In Experiment 2, intra-saccadic color changes will be artificially connected to saccade performance. If habituation generalizes across all visual features, these color changes should become invisible after repeated exposure. The ecological validity of habituation must be demonstrated since previous experiments involved the same saccade vector and direction monotonously across the entire session. In natural vision, however, saccades amplitudes are variable. Experiments 3 will test if visual motion can be coupled to specific saccade vectors even if these are performed in random order. Experiment 4 will test habituation against the theory of trans-saccadic visual masking. The visual input that we receive immediately after every saccade might mask the intra-saccadic motion stimulus. Intra-saccadic masking has been tested with stimuli that were presented only briefly. However, in natural vision, the visual scenery does not disappear briefly after saccade execution. In order to evaluate which theory holds true under conditions of natural vision, in Experiment 4, intra-saccadic masking and habituation will be measured when stimuli are presented either briefly or stationarily. In summary, the experiments described in the grant proposal will reveal whether the theory of habituation might explain why we do not perceive visual motion every time we perform a saccade. By taking into account natural visual conditions, the success of the proposed theory will be compared against opposing theories

• DFG Programme: Research Grants