Depth Perception in Frogs and Toads: A Study in Neural Computing

1 Introduction.- 2 Modeling Depth Perception in Frogs and Toads.- 2.1 Previous Models of Depth Perception.- 2.2 Depth Perception in Frogs and Toads.- 2.2.1 The role of depth perception in detour behavior.- 2.2.2 Monocular and binocular depth cues.- 2.3 Anatomy and Physiology.- 2.3.1 The eyes.- 2.3.2 Optic nerve projection sites.- 2.3.3 Nucleus isthmi - a source of binocular input to tectum.- 2.3.4 Binocular units in tectum and thalamus.- 2.3.5 Efferent pathways from tectum and thalamus.- 2.4 Functional Analysis of the Major Visuomotor Centers.- 2.4.1 Retina.- 2.4.2 Functions of thalamus and tectum.- 2.4.3 Evidence for depth perception in thalamus.- 2.4.4 Motor pathways from tectum and thalamus.- 2.4.5 Depth perception dissociated from orientation.- 2.4.6 Depth Maps, Motor activity and tectal retinotopy.- 2.4.7 Summary of the frog/toad visual system.- 2.5 Modeling Assumptions.- 2.6 Conclusions.- 3 Monocular and Binocular Cooperation.- 3.1 Design of the Model.- 3.1.1 Structure.- 3.1.2 Constraints.- 3.1.3 Coordinate systems.- 3.1.4 Computational scheme.- 3.2 Methods.- 3.2.1 Computer simulation.- 3.2.2 Visual input.- 3.3 Results.- 3.3.1 Initial validation.- 3.3.2 Effect of lateral excitatory spread.- 3.3.3 Depth segmentation.- 3.3.4 Effects of lenses and prisms.- 3.3.5 Barrier depth resolution.- 3.3.6 Monocular response.- 3.4 Discussion.- 4 Localization of Prey.- 4.0.1 Background.- 4.0.2 Model overview.- 4.1 Methods.- 4.1.1 Computer simulation.- 4.1.2 Mathematical description for the simulation.- 4.1.3 Graphical displays.- 4.1.4 Depth estimate categories.- 4.1.5 Visual input.- 4.2 Results.- 4.2.1 Experiments with single-prey stimuli.- 4.2.2 Experiments with multiple-prey stimuli.- 4.2.3 The effect of lenses on two-prey experiments.- 4.3 Discussion.- 4.3.1 A possible neural realization of the model.- 4.3.2 Suitability of the nucleus isthmi as a tecto-tectal relay for depth perception.- 4.3.3 Evaluation of the model.- 5 Towards a Complete Model.- 5.1 The Cue Interaction and Prey Localization Models.- 5.1.1 Unities.- 5.1.2 Diversities.- 5.1.3 A synthesis.- 5.2 An Extended Model of Accommodation Control.- 5.3 Experimental Verification of the Models' Depth Scale.- 5.4 Discussion.- 6 Conclusions.- 6.1 The Models and their Contributions.- 6.2 Suggestions for Animal Experiments.- 6.3 Suggestions for Robotic Algorithms.- A Modeling and Simulation Details.- A.1 Representation of a Neural Unit.- A.2 Representation of a Neural Layer.- A.3 Numerical Methods.- A.4 The Cue Interaction Model.- A.5 The Prey Localization Model.- B Simulation Optics.- B.1 Optical Geometry.- B.2 Representation of Prisms.- B.3 Retinal Projections.- B.4 Disparity Input Planes.- B.5 Accommodation Input Planes.- B.6 Representation of Lenses.- B.7 Conversion from Internal to External Coordinates.- B.8 Nominal Parameter Settings.