GABA-antagonist inverts movement and object detection in flies.

Movement detection is one of the most elementary visual computations performed by vertebrates as well as invertebrates. However, comparatively little is known about the biophysical mechanisms underlying this computation. It has been proposed on both physiological and theoretical grounds that inhibition plays a crucial role in the directional selectivity of elementary movement detectors (EMDs). For the first time, we have studied electrophysiological and behavioral changes induced in flies after application of picrotoxinin, an antagonist of GABA. The results show that inhibitory interactions play an important role in movement detection in flies. Furthermore, our behavioral results suggest that the computation of object position is based primarily on movement detection.