Abstract
Grooming is a complex and robust innate behavior, commonly performed by most vertebrate species. In mice, grooming consists of a series of stereotyped patterned strokes, performed along the rostro-caudal axis of the body. The frequency and duration of each grooming episode is sensitive to changes in stress levels, social interactions and pharmacological manipulations, and is therefore used in behavioral studies to gain insights into the function of brain regions that control movement execution and anxiety. Traditional approaches to analyze grooming rely on manually scoring the time of onset and duration of each grooming episode, and are often performed on grooming episodes triggered by stress exposure, which may not be entirely representative of spontaneous grooming in freely-behaving mice. This type of analysis is time-consuming and provides limited information about finer aspects of grooming behaviors, which are important to understand movement stereotypy and bilateral coordination in mice. Currently available commercial and freeware video-tracking software allow automated tracking of the whole body of a mouse or of its head and tail, not of individual forepaws. Here we describe a simple experimental set-up and a novel open-source code, named M-Track, for simultaneously tracking the movement of individual forepaws during spontaneous grooming in multiple freely-behaving mice. This toolbox provides a simple platform to perform trajectory analysis of forepaw movement during distinct grooming episodes. By using M-track we show that, in C57BL/6 wild type mice, the speed and bilateral coordination of the left and right forepaws remain unaltered during the execution of distinct grooming episodes. Stress exposure induces a profound increase in the length of the forepaw grooming trajectories. M-Track provides a valuable and user-friendly interface to streamline the analysis of spontaneous grooming in biomedical research studies.
Highlights
Grooming is an evolutionary ancient innate behavior performed by most vertebrate species, including humans [1, 2]
Each grooming episode consists of predictable and stereotyped movements that mice execute as they groom along the rostro-caudal axis of their body [4, 5]
The neuronal circuits that control grooming are mainly located in the basal ganglia nuclei
Summary
Grooming is an evolutionary ancient innate behavior performed by most vertebrate species, including humans [1, 2]. We assembled a simple experimental set-up and developed novel open-source software based on the use of a probabilistic-programming algorithm, which allows us to perform kinematic tracking of forepaw movements during spontaneous grooming episodes in multiple freely-moving mice.
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