Complex sentence: For the elderly, especially those with Alzheimer's or other diseases that affect the memory, when the brain is introduced to exercise the hippocampus part of the brain can regain in size and improve memory.
Split into simpler sentences: For the elderly, especially ones that have Alzheimer's or other diseases that affect the memory. When the brain is introduced to exercise the hippocampus part of the brain can regain in size and improve memory.