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Introduction1

Department of Neurology, University of Michigan Medical School, Ann Arbor, MI

Titus John, Damien Ellens, Matt Gaidica, Sophia Peng, Daniel Leventhal

Evolution of limb kinematics during fine motor skill acquisition in rats

Methods

Multiple neural systems, including the basal ganglia, cerebellum, and corticospinal tracts, interact to acquire and consolidatemotor skills. Furthermore, many Movement Disorders (e.g., Parkinson Disease) impair motor skill acquisition and performance.To better study how motor skills are consolidated, we developed an automated rat skilled reaching apparatus. It improveson the well-developed and robust rat skilled reaching task by allowing unsupervised task performance and 3-D reconstruction ofreach trajectories. As a first step towards using this task to understand motor learning, here we describe changes in rat fore-limb kinematics as the skilled reaching task is acquired.

Trajectory-Reconstruction

Hypotheses1. Successful and failed reaches will converge on similar reach trajectories as success rate improves.2. Variability in failed reaches will decrease as reach success improves.

Future Goals

Individual reaches were recorded at 300 Hz.

Paws painted with green nail polish to allow automated motion tracking.

Trained for at least 14 days (100 trials/session, 1 session/day).

Digits were manually marked every 8 frames over a 40 frame interval after the paw passed through the slot on days 3, 5, and 7.

References

Acknowledgements : Parkinson Disease Foundation STA- 1592, Brain Research Foundation, NIH NINDS K08-NS072183

Hartley R., A. Zisserman, Multiple View Geometry in Computer Vision. 2003 Cambridge University Press

Klein A, Sacrey LA, Whishaw IQ, Dunnett SB. The use of rodent skilled reaching as a translational model for investigating brain damage and disease. Neurosci Biobehav Rev. 2012 Mar

Example of paw marking process. Shown above are the left, center, and right prespective of a

manually marked paw.

Results

Day 3 Day 5 Day 7 Day 3 Day 5 Day 7

Euclidian distance between successful and failed reaches.

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7Discussion

Individual learning curves for rats analyzed in study.Rats reaches were examined on Day 3,5,7 of the training.

Variance in indivdaul failed reaches compared to mean fail trajectory over days.

Averaged successful (red) vs. averaged failure (blue) reaches for n=6 rats.Demonstates convergence of successful and failure trajectories over days.

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Automated digit detection by tattooing each digit a different color and improving

camera calibration.

Digit Detection Automation

acquisition

acquisition

1) Examine cortico-striatal neural patterns during acquisition and consolidation phases of the task.

2) Modify the task to allow for different reach trajectories/perturbations during

Paw marking included the metacarpel along with the proximal and distal phalanges. The center of the back of the paw and pellet were also marked.

Trajectories of successful and failed reaches converged on a common path over days.

The variability in failed reaches did not decrease over days.

This suggests that the rat motor system converges on a mean rewarded trajectory, but variability in reach trajectory persists.

This persistent variability on some reahes may serve to search for more optimal reaching strategies or allow for adaptation to changing circumstances. Alternatively, the persistent variability may represent a “floor” effect of reproducibility achievable by the rat motor system.

Automated three dimensional reconstruction of individual digit positions (see Future Work) shows promise for monitoring motor skill acquisition and consolidation over time.