Preference for direction of movement on visual neurons of a crab.

MEDAN, VIOLETA; OLIVA, DAMIÁN; TOMSIC, DANIEL

Nyborg

Congreso; 7th International Society for Neuroethology Meeting; 2004

International Society for Neuroethology

Taking advantage of the experimental benefits offered by the crab Chasmagnathus to perform stable intracellular recordings from brain interneurons in the intact animal, we started to study the physiology of neurons implicated in the detection of movement. In previous studies we characterized the morphology and physiology of a group of lobula-giant movement detector neurons (MDNs) involved in the escape response elicited by a threatening stimulus moving overhead, and their relation to a long-term memory processes. In order to further investigate the visual system of the crab, in particular, the sensitivity of visual interneurons to image features, we built an experimental set up based on computer-generated visual stimuli that are projected, simultaneous or alternatively, by 4 monitors located in front, above and at both sides of the animal. This allows to deliver a whole variety of visual stimuli and to quickly switch the presentation of the stimuli across specific parts of the whole visual field, while the neuronal and/or the behavioral activity of the animal is being recorded. First results on MDNs indicates that according to their visual field and directional sensitivity, these neurons can be clearly divided in at least two categories. One category includes neurons with very large receptive fields and with low or null directional selectivity, whereas the second group is composed by neurons with much narrower receptive fields and a marked preference for the direction of movement. The results provide the first account in crustacea of interneurons sensitive to the direction of movement and illustrates the possibilities of this preparation to study visual processing with intracellular techniques.