A Modular Platform for In-plane Ground Reaction Forces Detection in a Mouse Model: Design, Development and Verification

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 increasing popularity. This work represents a first step towards the development of a sensorized 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 a few attempts have been made to measure GRFs 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, modular, mechanically simple, two-axis force sensor for measuring the in-plane components of GRFs was designed and developed. Special care was paid to design a structure that allowed self-aligned assembly, for repeatability and modularity for combining multiple platforms for a sensorized floor. Preliminary testing was performed with both Reeler and wild-type mice. Fourier analysis validated the hypothesis of a direct connection between tremor and in-plane GRFs. Data analyzed and filtered highlight a peculiar spectrum frequency in Reeler mice tremor, centered around 21 Hz. This tremor, which was never quantitatively observed and measured before, is completely absent in wild-type mice.