This has more than 360 puzzles to offer a variety of complex stimulation for your brain.
"In some of the games, there is some testing that can identify the areas you need to work on," says Dr Grey.
"As we age, we decline at different rates, so this identifies where you are weak and focuses on strengthening those areas. It also tracks your results over time. This is really good, because if you're concerned about a decline you can show the results to a doctor."
2: Lumosity
Free, though some games cost extra, available on the web for Android and iPhone
This is a series of more than 40 games, such as matching shapes, designed to improve your memory, problem- solving, processing speed and flexibility of thinking.
You can select specific memory functions you want to improve, such as remembering names and faces, and it designs daily workouts tailored to you.
"This is based on well-known neuro-psychological principles, so to be able to play these every day at home is a real game-changer," says Dr Grey.
3: A Word A Day
Free for Android on Google Play
This gives you a new word each day, along with its meaning and examples of how it's used. You can then test your knowledge with quizzes.
Though vocabulary doesn't decline with age, this app "will improve language skill and memory centres in the brain," says Dr Grey.
This is because the part of the brain responsible for language communicates with other areas of the brain.
4: Happify
Free, available for Android, iPhone and iPad
This app is designed to improve psychological well-being. It recommends different daily activities (such as listing what you're grateful for each day) depending on the goal you set yourself, such as reducing stress. "This is evidence-based and personalised, which I like," says Dr Grey.
5: CogniFit Brain Fitness
Free, available on the web, iPhone and iPad
Through games such as sudoku and hand-eye co-ordination skills, this app tests concentration, perception and memory. You can compare your cognitive function with the ideal for your age and it builds a brain-training regimen based on your performance.
"This tests different cognitive performance skills. People get bored with games, therefore variation is good," says Dr Grey. "Spending 15 to 20 minutes a day on this really does help."
- Daily Mail