253 | Intensity and polarization cue summation enhances object discrimination

Sensory and Motor Systems

Author: Martin Beron de Astrada | Email: martinba@gmail.com

Martín Berón de Astrada , Benjamin Vidal , Rodrigo Pampin , Pablo Riccio , Verónica Pérez Schuster

1° IB3, Dpto FBMC, FCEyN, UBA

The usage of polarized light to enhance object or motion detection, termed object-based polarization vision, has been recognized in a number of animals inhabiting intertidal and aquatic environments. However, the visual computations and neural mechanisms underlying such capabilities remain unknown.
In the last couple of years we have been studying the polarization contrast sensitivity in the grapsid crab Neohelice granulata. We quantified the escape response and the changes in heart rate of animals evoked by a looming disk with an 82° polarization difference between the object and the background. More than 90% of the animals responded by freezing or escaping. We co-rotated the e-vector of light from object and background and found that the escape response varied periodically with a 90º period. Maximum responses were obtained for object and background e-vectors near the vertical and horizontal orientations. The cardiac response matched these results. In line with theoretical models, our results provide experimental evidence that crabs perform a two-channel (vertical/horizontal) computation to achieve object-based polarization vision maximizing sensitivity in its natural environment (Basnak et al., 2018).
To study how polarization contrast (PC) is combined with intensity contrast (IC) information we modified a 3D monitor to modulate differentially the intensity of vertical and horizontal polarized light. We confronted animals with edge motion stimuli translating laterally.