Automated recognition of rat and mouse body landmarks using 2D kinematic model

T. Mukhina and K. Anokhin

P.K. Anokhin Institute of Normal Physiology, Moscow, Russia

Video tracking is an important tool for automation of animal behavioral experiments. However, in most of existing video tracking programs an animal is represented only by a gravity center of its body. This does not allow to characterize animal behavior in terms of its postures and restricts automated classification of behavior. The present paper describes an approach to video tracking of experimental animals (rats and mice) by means of 2D kinematic model. This approach allows to recognize automatically several animal body landmarks and serves as an aid towards better discrimination of its postures.

Kinematic body models have been widely used to characterize human postures and movements. However, body of a human consists of fairly rigid parts which can be relatively easy simulated using geometrical figures. On the contrary, rat or mouse body is ‘soft’ since its visible surface in most cases does not conform to the shape of its skeleton. In the current work identification of mouse body parts was performed using two-dimensional kinematic model of the animal developed by the authors. The model accounts for anatomical features of an animal and has 8 degrees of freedom describing position of animal in space as well as shifts and relative rotations of different body parts and landmarks such as base of the tail, nose, waist and neck. The model fairly well describes relative position of different parts of the moving animal body. It can be used to find the animal’s head and tail, recognize turns of the body and head and several forms of exploratory behavior (e.g. stretching, rearing). One of the features of this approach is that it does not require attachment of physical markers to the animal body, which significantly expands its possible applications.

The paper will include a description of the developed model and its application for automatic recognition of certain forms of behavior in mice and rats.

Paper presented at Measuring Behavior 2005 , 5^th International Conference on Methods and Techniques in Behavioral Research, 30 August - 2 September 2005, Wageningen, The Netherlands.

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