Control of fixational eye movements and posture

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In this renewal proposal, we apply for a continuation of the research on fixational eyemovements (FEM) as part of the Research Group. Results from the first funding period of the project are related to three topics. First, we developed new methods for the analysis of FEM and microsaccades during fixation tasks and scene viewing. For example, a wavelet-based characterization technique demonstrated that interindividual differences can be reduced to few principal components of the microsaccades' shapes. Second, we demonstrated the relevance of FEM to saccadic reaction times. Microsaccades contribute to the saccadic facilitation effect in natural scenes. Furthermore, our results suggest that FEM serve an important role in noise-enhanced perception. Finally, we developed an integrated model of FEM and microsaccades based on a self-avoiding walk in a potential. In the second phase of the project, model-driven investigations will play a key role for our research program. First,we plan to run a series of experiments that use gaze-contingent display changes to influence microsaccade statistics (e.g., rate, amplitude, orientation). For all of the planned experiments, specific model predictions can be obtained. We expect that the effects of display changes on FEM might be reproduced in the model by a reset of the activation field; an attentional shift might be described by transient changes of the potential. Second, we will compare properties of microsaccades across tasks (reading, scene viewing, visual search) based on the developed tools for the characterization of microsaccades. Third, we plan to run follow-up studies on the coupling of FEM and posture and will extend the Investigations to other physiological parameters (pupil, heart rate).