EE ZOOM Seminar: Visual system's mechanisms and computational models for Spatio-temporal visual phenomena
Join Zoom Meeting
https://proofpoint.zoom.us/j/607284105
Speaker: Hadar Cohen-Duwek
Ph.D. student under the supervision of Hedva Sptizer and Alex Bronstein
ZOOM Seminar
Wednesday, 22nd April at 12:00
Visual system's mechanisms and computational models for Spatio-temporal visual phenomena
Abstract
The research goal was to offer mechanisms and computational models that predict several visual spatio-temporal phenomena, which are a subgroup of the "visual illusions” phenomena. (Visual illusions enable us to identify underling neuronal mechanisms of the visual system).
We focused on the “watercolor illusion”, the positive and the negative "aftereffect illusions" and the “reversed phi illusion”. The first group of illusions that we focused on involve the "creation" of surfaces which are triggered by edges, in both spatial and spatiotemporal domains. This type of effects are termed as filling-in processes. The second type of effects is directional motion effects and retinal processes. We suggest that the connection between these two types of effects derives from their common mechanism’s components.
For the filling in effects, we suggest a computational model that is based on a Poisson equation as heat source. Our proposed computational model is able to predict most of the filling-in effects that derive from edges, such as the assimilative and non-assimilative watercolor illusions, and the positive and negative aftereffects.
For the motion effects, we developed a computational model supported by simulations, which for the first time leads to correct predictions of both the behavioral motion effects (phi and reverse-phi), and the relevant electrophysiological and anatomical findings. This has been achieved through the well-known neuronal response: the rebound response (or "Off response"). For testing this hypothesis, we proposed a psychophysical experiment on human subjects, which demonstrated the abolishing of the aftereffect phenomenon through a noise mask. The experimental results confirmed the theoretical predictions regarding the role of the rebound mechanism. We furthermore suggest that the reverse-phi effect is only an epiphenomenon of the rebound response of the visual system. Our findings, thus, shed new light on the comprehensive role of the rebound response as a parsimonious spatiotemporal detector for motion and additional memory tasks, such as for stabilization and navigation.
