Neuronal circuits involved in visual movement detection processing in a crab

BERÓN DE ASTRADA, MARTÍN, VIOLETA MEDAN Y TOMSIC DANIEL

Huerta Grande, Córdoba

Congreso; Primer reunión conjunta SAN-TAN; 2009

Sociedad Argentina de Neurociencia y Taller Argentino de Neurociencia

Animals permanently evaluate their surroundings in order to produce an adaptive behavior. Detecting object movements is a task that visual systems need to solve rapidly to fittingly guide behavior. We study the escape response of the crab Chasmagnathus to visual stimuli. Previously, we developed an experimental preparation that allowed us to perform intracellular recordings in the intact living animal. With this methodology we found that a generic group of large motion-sensitive neurons from the crab brain respond to visual stimuli and accurately reflect the escape performance. Moreover, these neurons play a key role in visual learning and memory and in the decision to initiate an escape. In particular, we have identified 4 classes of large motion-sensitive neurons. Morphologically, all these classes consisted in large horizontal (tangential) arborizations in the deepest optic neuropile with axons projecting toward the midbrain. Because these axons are thin and a long distance separates the optic lobes from midbrain the elucidation of their projection pattern could not be accomplished in the past. Recently, we have started solving these difficulties using dextran fluorescent conjugates of high molecular weight. Here, we present the first results obtained with this technique that allow us to identify in which areas of the midbrain this neurons are projecting to.                        The present results open the posibility to trace these neurons with calcium sensitive dyes conjugated to dextrans of high molecular weight, which will allow to further study its physiological activity in an intact living animal.