I also read on a post here that maintaining contact with a POI is important throughout the admissions process, but I only contacted them before applying to determine whether or not they were accepting students next fall.
Also, I would have to echo the sentiments of the other posters here - I don't think it's necessary to contact them now since your application is already in and they are already very busy at this time. I don't think it will help it all and it may be an annoyance, if anything. There are often hundreds of applicants to a program - is a POI really going to remember your name amongst the others, on top of other responsibilities, such as grants, current students/advisees, classes, research, various other commitments, etc.?
If you did not contact the POI before applying, I don't know if contacting them now will make a positive difference. The only instance where I would suggest an applicant contact a POI is if they are an exceptional fit for the program.