Abstract
BackgroundIn the rat, the single-pellet reaching task includes orienting, reaching, grasping and retracting movements. It has previously been described by notation techniques, high-speed video and cineradiographic recordings. Recently, high-definition cameras have been used to track paw and digit movements with DeepLabCut, a machine-learning algorithm for markerless estimation of paw position. New methodOur new approach consists of positioning three high-speed infrared digital cameras to track the full motion of markers on the rat’s body. This provided a previously unavailable 3D recording of skilled reaching kinematics in the rat moving freely in the reaching box, which were analysed by Qualisys Track Manager software and MATLAB. ResultsThis method enabled description of kinematic parameters unobtainable without motion tracking and provided insight into the spatiotemporal metrics of movements used to perform skilled reaching. It revealed that orientation features three steps and reaching has two bimodal start-point distributions, one along the horizontal axis and one along the vertical axis. At the end of reaching, the wrist/paw occupies the same position as the nose at the end of orienting. In grasping, averaging trajectories confirmed the marker lowering and target approaching. Comparison with existing methodsOur method required significantly reduced time to label data and obviates the need for off-line manual marking of videos. It provides an efficient means of capturing volumes containing the entire range of marker movements. ConclusionsThis study validated a new and efficient approach for quantifying rat movement kinematics, useful for comparing preclinical and clinical conditions.
Highlights
Skilled reaching, the act of reaching to grasp an object as occurs in a reach-to-eat task, shares many similarities among both primates and rodents (Whishaw and Pellis, 1990; Whishaw, 1996)
Skilled reaching has been previously described in rats by means of notation techniques (Whishaw et al, 1992; Gharbawie and Whishaw, 2006), video (Whishaw et al, 2008), as well as cineradiographic recordings (Alaverdashvili et al, 2008)
To determine if wrist/paw position at the end of reaching tended to occupy the same spatial position as the nose at the end of orienting, first we present two frames corresponding to Poke end and reaching end, respectively (Fig. 11A and B); we plotted the cumulative normalized displacements of the nose marker during orienting and wrist marker during reaching on the horizontal, depth and vertical axes separately and in three dimensions (Fig. 11C–F)
Summary
The act of reaching to grasp an object as occurs in a reach-to-eat task, shares many similarities among both primates and rodents (Whishaw and Pellis, 1990; Whishaw, 1996). The single-pellet reaching task includes orienting, reaching, grasping and retracting movements It has previously been described by notation techniques, high-speed video and cineradiographic recordings. New method: Our new approach consists of positioning three high-speed infrared digital cameras to track the full motion of markers on the rat’s body. This provided a previously unavailable 3D recording of skilled reaching kinematics in the rat moving freely in the reaching box, which were analysed by Qualisys Track Manager software and MATLAB. Results: This method enabled description of kinematic parameters unobtainable without motion tracking and provided insight into the spatiotemporal metrics of movements used to perform skilled reaching It revealed that orientation features three steps and reaching has two bimodal start-point distributions, one along the horizontal axis and one along the vertical axis. Conclusions: This study validated a new and efficient approach for quantifying rat movement kinematics, useful for comparing preclinical and clinical conditions
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