INVESTIGADORES
BERON DE ASTRADA Martin
congresos y reuniones científicas
Título:
Polarization vision as a source of visual contrast in arthropods
Autor/es:
BERÓN DE ASTRADA
Reunión:
Congreso; Congreso Argentino de Neurociencias; 2020
Resumen:
The polarization of light is a quality of light invisible for the human eye. However, the usage of polarized light to enhance visual contrast has been recognized in a number of animals inhabiting intertidal and aquatic environments. So far, 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) we confronted animals with motion stimuli. We identified two different phases of the crab?s cardiac response. The first phase might correspond with behavioral freezing while the second one with animal?s escape response. The former was elicited by light flashes, both polarization and low intensity contrast edge motion. Instead, the second phase of the response could only be elicited with high IC stimuli and, as is typical of the escape response, was largely reduced by repeated stimulation. The addition of polarization cues to an IC stimulus enhanced significantly the first but not the second phase of the response. These results indicate that polarization contrast information is used for an initial alert response but not for a second, more elaborated, phase of processing of visual information.