Differential visual adaptation mechanisms in an artrhopod.

MERCEDES BENGOCHEA Y MARTÍN BERÓN DE ASTRADA

Huerta Grande

Congreso; Congreso Argentino de Neurociencias, 2012; 2012

SAN

Crabs are highly visual animals that display complex visually guided behaviours. They have well-developed compound eyes located on mobile stalks, containing an important part of their nervous systems. Just bellow the retina, there are three serially arranged retinotopic optic ganglia. Previous work revealed the existence of giant neurons in the third optic ganglion (LGs) that command the crab?s escape response to a visual danger stimulus (VDS). This response declines after a few stimulus presentations giving rise to a short or long term memory depending on the training protocol experienced. This behavioural modification is a consequence of plastic changes in LGs movement sensitive neurons. However, a number of evidences suggest that the changes induced by massed training occur in columnar elements that are presynaptic to the LGs neurons. The aim of this work is to study the presynaptic site of plasticity. To stain these presynaptic columnar elements, we applied dextrans tracers onto the first optic ganglion in order to obtain a massive staining of neurons that project from this ganglion to the second one. We found that these columnar neurons arborize in three different horizontal layers. Studies with calcium imaging showed that the response of these columnar neurons does not decline with successive stimulus presentations. This result indicates that the site of plasticity is between these columnar neurons and the LGs.