A comparison of video and magnetic search coil recordings of mouse eye movements

Interest in connecting molecular biology and behavior is motivating researc h into the eye movements of mice. Unfortunately, recording eye movements in this diminutive animal is technically difficult. We present the first meth od for obtaining calibrated video oculography, and contrast the results wit h simultaneously obtained scleral search coil recordings in C57BL/6 pigment ed mice. We determined the distance of the pupil from the center of corneal curvature, based upon relative motions of the pupil and corneal reflection s during camera movements, and used the distance to convert subsequent vide o measurements of pupil motion to eye rotation. We recorded responses durin g sinusoidal rotation (0.1-1.6 Hz) in the light, by video prior to search c oil implantation, and by video and search coil simultaneously following imp lantation. Pre-implantation, video-derived gains ranged from 0.86 +/- 0.03 (mean +/- SD) at 0.1 Hz to 0.95 +/- 0.03 at 0.8 Hz. Phase progressed monoto nically from - 3.1 +/- 2.6 degrees (eye leads head) at 0.1 Hz to + 5.9 +/- 1.1 degrees at 1,6 Hz. Coil implantation reduced the range of video-derived gains to 0.64-0.79. This reduction reflects disruption of normal behavior by the coil. Coil data confirmed the video results. Video and search coil t echniques each have advantages. Specific precautions are required when desi gning and interpreting experiments using the coil technique. (C) 2000 Elsev ier Science B.V. All rights reserved.