Visual learning and memory assesed by in vivo calcium imaging from individual interneurons in the crab Chasmagnathus (poster)

A. DELORENZI, L. SMAL, J. SZTARKER, M. BERÓN DE ASTRADA, D. TOMSIC, H. MALDONADO

San Diego, Estados Unidos.

Congreso; Society for Neuroscience 34rd Annual Meeting; 2004

Society for Neuroscience

Visual stimuli are thought to be internally represented in the brain by spatiotemporal activity patterns of neurons. Identification of learning-induced synaptic changes in neurons involved in internal representations is at the forefront of memory studies. Here, we show an optical imaging study performed in vivo from neurons that participate in visual learning and memory. In the crab Chasmagnathus, a visual danger stimulus initially leads to an escape response. After repeated presentations of the stimulus (US) the escape response is replaced by freezing, building an associative longterm memory between the context (CS) and the US. Recently, Chasmagnathus wide field movement detector neurons (MDNs) were both morphologically and functionally characterized (Tomsic et al., 2003): MDNs respond to the training stimulus reflecting the behavioral changes related to learning, short- and long-term memory, suggesting that plastic changes in MDNs may account for the behavioral modifications. Here we investigated the issued by using optical imaging techniques. MDNs were loaded with Calcium Green and a small window in the eyestalk carapace was gently opened to gain visual access to lobula (L) and lateral protocerebrum (LP), where MDNs processes are located. Spatiotemporal activity patterns of MDN were recorded in vivo during learning and short-term memory. Results reveal that both massed and spaced training elicited modifications of MDNs activity -assessed by intracellular calcium concentration- that resemble the electrophysiological activity and the behavior: a) only spaced training yield enduring changes; b) training-evoked decrement was stimulus-specific. In addition, training effects could be observed in different neuronal compartments both in L and LP neuropils.