Permanency of gait improvement induced by vestibular stimulation in the mutant mouse staggerer

Among the several methods that have been used to investigate the impact of environmental enrichment, on the behavior of an animal, the use of behaviorally deficient mutant mice has been especially useful. The use of this model allows one to investigate functional recovery compared to a known baseline (the normal animal) without the trauma and imprecision associated with surgical intervention. The present study extends a previous investigation that demonstrated a significant improvement in certain measures of the gait of the cerebellar mutant mouse staggerer, as a result of daily vestibular, muscular and visual stimulation. The results of the present study concerned the durability of that observed improvement. No clear-cut conclusion as to the permanency of the stimulation's effects could be drawn, because results differed according to the measures used. When tested two months after the end of the stimulation period the mutants ran more slowly, with as many "errors" as unstimulated mutants, leading one to infer a deleterious effect of the stimulation. On the other hand, if one considers only the number of "errors" during the test, one may conclude that early stimulation has a permanent advantageous effect of increasing the staggerer's receptivity to further stimulation. Other measures lead to more ambiguous conclusions. Finally, it is argued that even though true improvement in the staggerer's gait can be inferred from these results, and that at least some aspects of that improvement seem to be long-lasting, the generality of the findings cannot validly be extended beyond the precise experimental conditions.