|MadSci Network: Neuroscience|
Dear Jeff, Research with rodents and mazes is typically done with both mice and rats, so either one will be fine. (I personally prefer rats because they are not as smelly as mice, though mice are cheaper.) Since you will be averaging maze completion times to compare the pre-trained rats to the novice rats, you should have as many as you can feasibly take care of. I'd say at least 5 in each group. Otherwise, you may not get significant results between groups. Make sure all the rodents you purchase are the same age. When you order them from a science supply company (like Carolina Biological Supply), they will all have similar genetic characteristics and you can be assured they are the same age. You need as much biological consistency as possible between your subjects. So in other words, don't purchase them from your local pet store but order them from a science supply place. You'll also want to keep them in identical environments, serve them identical food, etc.
Try the links in the MadSci Library for more information on Neuroscience.