Contactless method for the continuous and selective study of motor activity in the laboratory rat

The author suggests a system for the continuous, direct, long-term recording of the motor activity of a particular laboratory rat in a group. A pickup of the animal's presence and its motor activity in the given space supplies a desired signal coded by frequency modulation of the carrier frequency. Detection is effected by a phase lock. The carrier frequency of a controlled oscillator is altered within small limits by means of inductive coupling between the tuning coil of the oscillator and a shading ring. The shading ring, which marks the experimental animal, is oval and is made of thin insulated litz wire sutured in place subcutaneously on the animal's back. The coil of the controlled oscillator surrounds the whole of the space in which motor activity is recorded. As an example, in a study of maternal behaviour, the presence or absence of the female in the nest and the motor activity of the lactating female typical of washing the young and of suckling them are identified and compared with direct observations.