| This thesis examines the behavioral consequences of motion sensitivity of salamanders' visual neurons. The analysis is centered on a correlation-based motion detector model of motion-sensitive retinal ganglion cells (RGCs). This model is then integrated with Ijspeert's model (Ijspeert, 2001) of spinal central pattern generators (CPGs) for salamander walking and swimming. The integration in the salamander brain is studied by means of a model of a sensorimotor pathway centering on the tectum. Vision is used to control locomotion, while locomotion strongly affects vision.;Salamander undulatory locomotion may involve substantial side-to-side head movement (Frolich & Biewener, 1992; Gillis, 1997; D'Aout & Aerts, 1997). Chapter 2 explores the effect of the side-to-side movements on the activity of motion-sensitive RGCs. In chapter 3, we consider the effects on locomotion gaits. We hypothesize that visual control of the direction of salamander motion occurs when the side-to-side head movement changes direction, a time of relatively low background motion motion. I.e., we propose that visual control of locomotion is suppressed at times of high retinal slip. This hypothesis is supported by our simulation results and related analysis.;In chapter 4, we demonstrate how the model of chapter 3 can generate behavior that has been interpreted as numerical cognition (Ansari, 2008). Our results support the hypothesis that the observed numerical preferences of salamanders are emergent properties of the early visual system, rather than evidence of higher cognitive ability. |
