The Hippocampus

The hippocampus is a region of the brain essential for memory. There is a hippocampus on both the left and right side of the brain. Many of the disease processes associated with dementia affect the hippocampus, however, the affects may be subtly different depending on the disease process (see the images below). Notice that on an MRI scan the left side of the brain is shown on the right of the image and vice-versa.

Healthy hippocampi

Shrinkage of both hippocampi

More shrinkage in the left hippocampus

More shrinkage in the right hippocampus

Hippocampal shrinkage on both sides is common in typical Alzheimer's disease, although it may also occur in other conditions, including dementia with Lewy bodies.
People with behavioural variant fronto-temporal dementia may also have hippocampal atrophy on both sides, although often this tends to be worse at the front of the hippocampi than at the back.
More often, people with a fronto-temporal dementia have noticably more shrinkage on one side of the brain than the other.
If the left side of the brain is affected more than the right, speech and language may be more affected than memory or behaviour.
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