A mechatronic system for in-plane ground-reaction-force measurement for tremor analysis in animal models

Movement and behavior analysis is a key research area in the domain of biomedical engineering and in many other medical research domains aiming at the understanding of physiological motor and cognitive basic mechanisms. The systematic application of robotic and mechatronic technologies to realize new tools and measurement methods for quantitatively assessing motor and cognitive functions in humans as well as in animal models is gaining an increasing popularity. This work represents a first step towards the development of a sensorised environment for behavioral phenotyping of animal models. In particular, this paper focuses on tremor analysis in reeler mice, an emerging potential animal model for anatomical and behavioral traits observed in autism. Ground reaction force (GRF) sensing is indeed the most direct means of measuring tremor. Although force platforms have extensively been used for large size animals, only few attempts have been made to measure GRF at a single paw for animals as small as mice or rats. Under the hypothesis that in-plane GRF components are directly connected to tremor, a small size, low-cost, 2-axis force sensor for measuring the in-plane components of GRF was designed and developed. Special care was paid to design a structure that would allow self-aligned assembly, for repeatability, and modularity for combining multiple platforms for a sensorised floor. Preliminarily testing was performed with both reeler and wildtype mice. Fourier analysis was deployed to extract information due to tremor, validating the hypothesis of a direct connection between tremor and in-plane GRFs.