Characterization of the activity of lobula columnar elements evoked by different parameters of visual stimulation that influence evasive behaviour in crabs

MERCEDES BENGOCHEA; DAMIAN OLIVA; MARTIN BERÓN DE ASTRADA

Montevideo

Congreso; XII International Congress of Neuroethology; 2016

International Society for Neuroethology

Object motion detection provides essential cues for a wide variety of behaviors such as mate, prey, or predator detection. In insects and decapod crustaceans, encoding of object motion is associated to visual processing in the third retinotopic optic neuropil, the lobula. Due to the thin caliber of the small-field lobula columnar neurons, almost all we know about object motion detection arises from studies on their postsynaptic and larger lobula output neurons. Here we used calcium imaging to study the activity of the columnar neurons that feed onto the crab?s lobula when stimulated by different parameters of object motion. We presented vertical edges translating horizontally that varied in speed, contrast and direction of motion. The high-speed edges produced the strongest calcium responses; the dark edges evoked greater responses than the clear ones; and calcium responses adapted to motion in one direction partially recovered when confronted to an edge running in the opposite direction. As lobula output neurons have been implicated in driving evasive behaviors, we also studied the modulation of the crab escape behavior to variations in the same visual parameters. We found a high correlation between the activity of the columnar neurons and the intensity of escaping. These results are consistent with the involvement of the lobula in object motion coding. Moreover, as the neurons studied originate in the second optic neuropil, the medulla, object motion information would indeed begin to be encoded in the medulla.