Monitoring home cage activity of laboratory rats

An open source, low cost solution for the development of a recording system for the purpose of unobtrusive continuous monitoring of home cage activity of rats.

A large number of different applications today include measurement solutions for pressure, temperature, humidity, inertial and strain-gauge sensors as well as transducers for velocity, acceleration, vibration, flow position and inclination by using Micro-Electro Mechanical Systems sensors (MEMS) that can be integrated (with all the necessary circuitry) to sensor nodes. The contribution of the current study is to demonstrate the use of sensor nodes as a necessary tool for the minimization of hardware costs for a laboratory recording system, given that similar commercial solutions available to researchers have high acquisition and maintenance/service costs. More specifically, by using MEMS accelerometers attached to standard laboratory rodent cages, we are able to continuously record home cage activity over several days of experimenting and detect the effect of various interventions (drug treatments, stressors, etc.). The advantage of such implementation is that activity can be monitored without the need of removing rats from their familiar home cage environment in order to place them in commonly used IR-based activity-recording arenas. The use of different G levels for acceleration sensors as well as the self-orientation ability that implemented, qualifies the proposed system expandable and suitable for large scale experiments. Data acquisition is obtained by means of commercial 8-bit microcontroller and stored into ordinary microSD cards while simultaneously acquired data is passed to the USB port for further transmission. Apart from its initial benefit of low cost, the proposed system is superior to similar recording systems (i.e. IR based) in the frame that is attached to rat cages without disturbing the surrounding environment of the rat model and it is not vulnerable.