Development of a three-dimensional jaw-tracking system implanted in the freely moving mouse

A high-resolution mandibular tracking system was designed and tested in a f reely moving mouse. A sensor unit, which consisted of four small magnetic s ensors, was employed to trace small magnet movements in the three-dimension al space. After the sensor's output-to-displacement transformation equation s were obtained from a multiple regression analysis of pre-experimental cal ibration data, the magnet and the sensors were transferred to the mouse, br ing kept at the same configuration as determined in the calibration system. In order to measure the three-dimensional jaw movements, the magnet was gl ued on the mandibular surface of the mouse and the sensor unit was implante d in the nasal bone. Jaw-movement trajectories were obtained as electrical signals from the sensors after being compensated by the output-to-displacem ent transformation equations of the sensors with a personal computer. This sensor system, applied to the Freely moving mouse, could trace the jaw traj ectories with an accuracy of better than 20 mum in three-dimensional space. Consequently, the typical pattern of the rhythmical jaw movements of the m ouse during mastication was obtained. The mouse protruded the mandible to t he most anterior position in the jaw-opening phase and retruded to it the m ost posterior position in the jaw-closing phase. This tracking system may also be applied to other small animals. (C) 2001 I PEM. Published by Elsevier Science Ltd. All rights reserved.