I would like to know whether environmental enrichment in a cage in the study of chronic toxicity affects the results of behavioral tests. Maybe you know the literature on this topic?
The cages with enriched environment in large studies or chronic are a decision of research, this go in the other way for welfare of animals, is a controlled variable, if your animal control are in the same conditions you should not be worried. Any way see the links of Dr. Ali and can decide or choose.
In your case, environmental enrichment would be a confounding variable to your study. Reynaldo suggests it will be a controlled variable and that might be true but there is no way to tell if it is equally beneficial to animals with damaged brains and animals with normal brains.
Yes, of course if the study will be conducted in animal with brain lesion is not recommended will use some environmental enrichment devices. In the other way the space by animal cage is other element to have in account, etc.