Brain games stimulate different cognitive functions, such as executive functions and processing speed, in older adults. And they can enhance your life in other ways. A brain exercise is any activity that engages your cognitive skills. Online brain games are popular and offer a wide variety of imaginative exercises designed to challenge your memory, focus and problem-solving skills, but tactile games like bingo and jigsaw puzzles and hobbies like model building also stimulate important types of memory skills. The key is that they must be difficult, but not too difficult.