Integration of multiple feature modalities in the visual system: New insights from experiments and modelling
Udo Ernst, University of Bremen (http://www.neuro.uni-bremen.de/content/dr-udo-ernst)
For understanding visual scenes, our brain has to integrate localized features into global percepts. For example in contour integration, oriented line segments are integrated into contours if they are aligned in a colinear and cocircular fashion. However, orientation is not the only visual feature available: also colour, spatial frequency, motion, and other features provide information about how to interpret a visual scene.
In this presentation, I will focus on two studies investigating how orientation alignment and spatial frequency (in)homogeneity are processed together in the visual system. By combining psychophysical experiments with computational modelling, we identify recurrent interaction schemes capable to explain the empiricial data in a quantitative manner. In particular, we find an effective inhibitory interaction between feature detectors preferring similar spatial frequencies for low visual contrasts. For high-contrast visual stimuli, these effective interactions become excitatory. Taken together, our results indicate a general principle for center-surround interactions which is similar for both, orientation and spatial frequency.
If time allows, I will conclude my talk by presenting some recent and surprising experimental results: contour integration, often considered to have a popout quality, is strongly attenuated in extended viewing of dynamical scenes. This result challenges current models of feature integration and the notion of contour integration being a predominantly stimulus-driven process.
11:00 – 12:00
Lunch will be provided after this event, in Mini Forum 2 (Level 4)