Arthropod's visual columnar neurons account for behavioral adaptability to repeated object motion

BENGOCHEA M; TOMSIC D; BERÓN DE ASTRADA M

Lund

Congreso; International Conference on Invertebrate Vision.; 2013

Object motion detection provides essential cues for a wide variety of animal behaviors such as mate, prey, or predator detection. In pterygote insects and decapod crustaceans, visual codification of object motion is associated to visual processing in the third retinotopic optic neuropil, the lobula. In this neuropil wide field tangential neurons collect motion information from small field columnar neurons and convey motion information to the midbrain where appropriate behavioral responses to visual stimulation would be finally elaborated. To our knowledge, in all the studied species (hoverflies, locusts, crayfishes and crabs) the repetitive presentation of object motion stimuli induces a retinotopic specific reduction in the response of the lobula tangential neurons that would account for the reduction in the animal response to the visual stimulation.        Whether the circuitry plasticity observed at the lobula tangential neurons first arises at these neurons themselves or as a consequence of plastic changes occurring in their presynaptic columnar neurons has been an elusive issue due to the difficulty to record the activity of the columnar neurons. Thus, we developed a simply methodology to directly address this issue recording the activity of columnar elements with calcium optical recordings. We found that the calcium response of the columnar neurons that fed visual information into the lobula rapidly declines to repetitive motion stimulus presentations. In correspondence with animal behavior and with the activity of lobula tangential neurons, the response of the presynaptic columnar elements completely recovers after fifteen minutes and the reduction in response is retinotopic specific. Conversely, the response of the columnar elements that convey information from the lamina (first optic neuropil) to the medulla (second optic neuropil) does not change upon repetitive visual stimulation. Our results indicate that the neural locus of decline in the response to rapidly repeated object motion observed in arthropods is the columnar neurons that fed visual information into the lobula. In line with previous studies, present results highlight the relevance of the neural plasticity that occurs at early stages of the visual pathways.