What kind of doctor do I need to take my Mom to as she is getting more and more confused?

Mom's not sleeping at night, and doing some odd things! Mom has depression, OCD, and anxiety disorder. She is 79 years old, has had one TIA and after that seems to be getting more and more confused, argumentative, sullen, and negative! Constantly rehashing things we have already talked about and her general answer lately is "I don't know" she lives with us and so it's a 24/7 thing. Any input would be appreciated!