Abnormal patterns of maze patrolling in the mutant mouse staggerer.

Two experiments describe the abnormal patterns of maze patrolling of adult mutant staggerer mice. The clinical symptoms of this mutant involve exclusively postural and gait abnormalities, apparently due to a disruption of cerebellar architecture leading to a vast reduction in cell numbers and size of this structure. This clinical feature can easily account for the first clear difference reported in these experiments, involving a reduction in the total ambulatory activity in a maze by this mutant. The more interesting result involves different qualitative aspects of the maze patrolling by staggers, compared to normal litter-mate controls. The experiments measured the distribution of subjects' visits to different maze locations, and varied the configuration and the amount of familiarization with the maze. Neither of these factors significantly influenced the basic results. These were the staggerers confined their ambulatory activity to a smaller number of different locations, which were more intensively visited compared to normals, and the staggerers showed a pronounced tendency to return to the place that was most recently visited, compared to a tendency by the normals to avoid that location. It is suggested that these results could be due either to abnormal novelty reactions or to a reduced tendency to pursue an initiated trajectory.