Hi!! I agree with Elena. The only thing that I will add is for the case, if you want to be more sure you can do exploratory behavior test which measures normal daily activity of rats such as licking, rearing, ambulatory activity, stereotypic activity e.t.c. It can again depend upon the basis of experiments you want to perform with rats(rota rod for muscle test, tail flick for sensitivity test, for stress there are several social behavioral test, for memory testing there are several mazes test like morris water, Y maze, T maze). Regarding EEG waves recording, for each wave there is certain range you can analse that whether the recording of waves lies in that range or not. If it lies, then recording is normal, provided that again you have to be very sure about the movement of rat while recording. Since, it the result changes with the activity of rat. In nutshell, a bit complicated because you have to acclamatize your rat to sit in same condition before you do any experiment with it. Generally, if rat is not normal then you get several clusters in recording but its a general overview.

Thanks a lot for your suggestion