Prof. Marion Silies - Johannes Gutenberg University Mainz, Germany: "Visual processing strategies in dynamically changing environments"

Speaker:

Prof. Marion Silies

Johannes Gutenberg University Mainz,

Germany

Title: Visual processing strategies in dynamically changing environments

A major challenge for the brain is to keep stable neural representations of stimulus features while facing a wide range of sensory inputs. Visual systems for example stably compute contrast and motion cues, while handling changes in background illumination. These changes occur slowly throughout the day, but also happen at millisecond time scales when our eyes saccade across a natural scene, or when the visual input changes rapidly due to self-motion. How does the visual system deal with such rapid changes caused by active behavior?

Here, I will discuss what can we learn from animals, in particular fruit flies, to stably process visual information under constantly changing conditions. Recently, we identified a mechanism that allows flies to handle rapid changes in illumination, faster than photoreceptor adaptation (Ketkar et al. 2020, 2022). This luminance gain control mechanism scales contrast signals when background luminance changes quickly. We have elucidated the circuit mechanisms that achieve luminance-invariant visual behaviors, and are currently investigating the biophysical mechanisms that combine different types of signals to achieve stable contrast computation

Stable contrast signals are then used to compute higher-order visual features, one of which is the direction of motion. I will show how motion computation is tuned to the behavior of the animal already in local direction-selective cells, which encode patterns of optic flow at the population level. Together, our work shows that visual processing strategies have evolved to handle the demands imposed by the animal’s own behavior.