Are prayer and fasting obligatory upon those afflicted with Down syndrome, and how does Islamic Sharia treat them in terms of rights and obligations?

If the person afflicted with the aforementioned disease—which causes a disorder in the brain and nervous system—is capable of learning and comprehending, then the religious obligations he is able to perform become incumbent upon him, and he has the same rights as other sane individuals. However, if the disease leads to insanity or mental deficiency, then religious obligations are waived for him. There remains a detailed discussion regarding his rights, such as the right to maintenance, while other rights, such as guardianship (wilayah), are waived for him.