Saccadic adaptation and visual perception

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Humans interact with the visual world through eye movements. Saccades are fast eye movements that re-direct gaze to new locations in the environment. Saccades are controlled by a network of visual, visuo-motor and motor areas of the brain. Plastic processes in this network ensure that saccades are accurately directed towards their goal. They do so by monitoring saccadic success and tuning saccade parameters to reduce errors. Recent results have shown that this tuning, called saccadic adaptation, not only affects saccade motor control but also higher stages of the oculomotor transformation that relate to visual space perception. The present proposal will investigate the processes behind saccadic adaptation and their relation to visual processing. Saccades are normally made to acquire new information about an object in the scene. Experiments on saccadic adaptation, however, have mostly been performed with simple and meaningless dot targets. Successful performance of a saccade in normal circumstances is directly related to the visual content of the saccade goal, its relevance to the task, and its motivational properties. The project will determine whether these factors affect the efficiency of saccadic learning. Secondly, the project will investigate the role that non-visual eye position signals play in the mechanisms of adaptation. After recent studies showed that saccadic adaptation is specific to the position of the eye in the orbit we need to investigate the specificity of eye position effects to saccade parameters amplitude, start and end point. Furthermore, we will investigate whether extraretinal eye positions signals even serve as a separate, non-visual learning signal for adaptation. Although the post-saccadic visual error is the main driving force of saccadic adaptation, eye position may provide additional information about whether the eye has reached the intended goal position. We will study whether this information is used by the oculomotor system. The third part of the work program will concentrate on the consequences of saccadic adaptation on perception and cognition. Previous studies have uncovered an influence of adaptation on perceptual localization, suggesting that errors of saccade targeting not only affect future saccade performance but also the visual perception of target locations. These findings suggested an intimate relationship between saccade planning and space perception. The proposal will search for possible similar relationships with two other aspects of visual function, namely visual search and visual working memory.