INVESTIGADORES
BERON DE ASTRADA Martin
congresos y reuniones científicas
Título:
In vivo Ca++ imaging responses to visual stimuli in columnar elements of the optic neuropils of an arthropod.
Autor/es:
MARTÍN BERÓN DE ASTRADA, MERCEDES BENGOCHEA AND DANIEL TOMSIC
Lugar:
Salamanca, España
Reunión:
Congreso; Ninth International Congress of Neuroethology; 2010
Institución organizadora:
International Society for Neuroethology
Resumen:
Experiments with insects and crabs demonstrate their remarkable capacity to learn and memorize visual features. However, brain areas and neurons underlying these processes remain unknown. In the crab Chasmagnathus, a visual danger stimulus (VDS) elicits animal escape which declines after a few stimulus presentations giving rise to a short or long term memory depending on the training protocol experienced (cita). In vivo intracellular recordings in the optic lobe of the crab show that this well studied learning and memory process can be extensively accounted for by plastic changes in lobula giants (LGs) movement detector neurons. However, a number of evidences suggest that the changes induced by massed training are presynaptic to the LG neurons. In arthropods, visual information is conveyed to the wide tangential neurons of the lobula by retinotopic narrow field columnar elements, which due to their small calibre are difficult to investigate with electrophysiological recordings. Thus, to investigate the possibility of plastic changes occurring in these columnar elements, here, we developed a preparation that allows assessing the response of these elements to visual stimuli using Ca++ imaging in the intact animal. First, as the retinal maps of crab optic neuropils were unknown, based on detailed tracing from retinal photoreceptors and neuronal projections along the optic neuropils we disclosed the crab retinal maps. Unexpectedly, we found that in the crab the chiasma between lamina and medulla reverses the order of horizontal retinotopic columns while the chiasma between medulla and lobula reverses the order of vertical columns. Second, to perform Ca++ imaging in the intact animal the crab was restrained and a small window was opened on the cuticle of the eyestalk. Trough this window, columnar neurons were stained with dextran Calcium Green, a Ca++ sensitive dye. We found consistent and clear responses from narrow field columnar elements from the lobula to different visual stimuli, including the VDS. The analysis of correspondence between the areas of columnar activation and the positions of stimulus presentation confirm the retinal maps derived from the anatomical studies. Ongoing studies are aimed at studying if these peripheral columnar elements are able to undergo plastic changes when confronted with repetitive presentation of a VDS.