A portrait of locomotor behaviour in Drosophila determined by a video-tracking paradigm.

This paper presents a detailed characterisation of locomotor behaviour of a single Drosophila fly freely walking in a small square arena. Locomotor activity is monitored by a video-tracking paradigm. Multiple parameters are extracted to construct the portrait of locomotor activity: the total distance moved, the number of episodes of activity and inactivity, the duration of activity, and the mean walking speed. To initiate a quantification of the fly's spatial walking movements, the number of passages in a virtual centre zone has also been determined. Moreover, to reveal the trajectory, as an index of fly's navigation ability, the turning angle, the angular velocity and the meander have been measured. Finally, we show that the number of episodes of inactivity as function of their duration follows a power law, while its counterpart, the episodes of activity does not, suggesting that the overall pattern of locomotor activity adheres to a fractal-like structure. Remarkably, the majority of these parameters are sexually dimorphic. This fine description of locomotor activity represents a new tool which will facilitate the study of the role of the different brain structures in the organisation of locomotor activity and the localisation of the fly's central pattern generator for locomotion and its motivational control.