Locomotor activity: a complex behavioural trait to unravel.

Locomotor activity in Drosophila, as in other organisms, is an important trait since it is at the basis of almost all behaviours. Indeed, the locomotor centre is implicated in all complex behaviours consisting of a change in the position of the animal with respect to its environment. Despite its importance, locomotor activity itself has received sparse attention for the following two reasons: first, until recently, the study of locomotor activity has lacked a well automated and standardised paradigm which is necessary for a detailed description. Second, locomotor activity is complicated by many factors (genetic, feeding, temperature), and as such is rather difficult to study. With recent technological developments, locomotor activity is now more accessible to automated paradigms. These have permitted us to reveal that locomotor activity is a very complex and rich behaviour that follows strict rules, harbours an organised (fractal-like) structure, and consequently might adhere to highly organised neurophysiological processes. Undoubtedly, locomotor activity has now reached a scientific maturity that allows it to be studied with the panoply of neuroethological approaches, in particular genetic, to unravel its mechanisms and neural circuitry. Consequently, we propose that locomotor activity can now represent a relevant biomarker to study various model diseases such as addiction, Parkinson, Alzheimer, Huntington, and diabetes.