The energy-based and feature tracking motion systems and their interactions

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Motion perception is undeniably crucial for many daily activities such as walking in a crowded environment, practicing a sport, crossing a street and driving. However, motion perception is complex. It is now well established that the visual system relies on two fundamentally different strategies to process motion, but the relative contribution of these two motion systems is still elusive. The current research program will investigate the underlying processes of motion perception to elucidate how the two motion systems interact. The central approach of this research program consists in developing novel psychophysical paradigms (i.e., non-invasive functional tests) to investigate the underlying factors affecting motion contrast sensitivity. Indeed, motion perception depends on many processing levels from the absorption of light by photoreceptors to neural processing in the cortex, and many factors along this path can affect the ability to perceive motion. These new psychophysical paradigms will be useful to precisely characterize the motion processes, and can also be useful to localize the underlying cause of a motion perception decline. Our ability to perceive motion changes with age. These psychophysical tools will be used to elucidate which processing stage is responsible for an age-related decline in motion perception. The current research program will build on our recent development of a powerful noise paradigm enabling to evaluate the impact of various properties of the visual system. This paradigm was developed for the low-level motion system. However, motion perception also relies on the feature tracking motion system, which is a high-level motion system that requires attentional resources. The first research axis will adapt our noise paradigm to characterize motion processing to the feature tracking motion system to evaluate the underlying factors affecting motion perception. By evaluating young and older adults (axis 2), we will be able to identify which underlying factors are responsible for age-related decline in feature tracking. The third research axis will investigate the relative contribution of the two motion systems as a function of eccentricity (i.e., peripheral vision), motion speed and luminance intensity. The last research axis will use the outcome of the third axis ton investigate the impact of healthy aging on the relative contributions of the two motion systems. In sum, this research program will provide fundamental knowledge about how the visual system processes motion and will quantify the effect of aging on the processing by the two motion systems and their interactions.