1. occipital lobes, 1
2. occupation (job/work), 1
   1. stress in, 1
3. oily fish, 1, 2, 3, 4
4. older/elderly people
   1. cognitive changes, 1
   2. learning new things, difficulties, 1
   3. normal vs abnormal signs and symptoms, 1
5. omega-3 and -6 fatty acids, 1, 2
6. openness, 1
7. orientation see disorientation; spatial orientation