Centric-minded Templates for Self-motion Perception

Paolo Cavalleri, Silvio P. Sabatini, Fabio Solari and Giacomo M. Bisio
DIBE - University of Genoa, Via Opera Pia 11a, 16145 Genova, ITALY

We propose a two-layer neuromorphic architecture by which motion field pattern, generated during locomotion, are processed by template detectors specialized for gaze-directed self-motion (expansion and rotation). The templates provide a gaze-centered computation for analyzing motion field in terms of how it is related to the fixation point (i.e., the fovea). The analysis is performed by relating the vectorial components of the act of motion to variations (i.e., asymmetries) of the local structure of the optic flow field. Notwithstanding their limited extension in space, such centric-minded templates extract, as a whole, global information from the input flow field, being sensitive to different local instances of the same global property of the vector field with respect to the fixation point; a quantitative analysis, in terms of vectorial operators, evidences this property as tuning curves for heading direction. Model performances, evaluated in several situations characterized by conditions of absence and presence of pursuit eye movements, validate the approach. We observe that the gaze-centered model provides an explicit testable hypothesis that can guide further explorations of visual motion processing in extrastriate cortical areas.