The hippocampus in Down's syndrome.

Evidence is presented from area measurements of the end folia (dentate gyrus) and pyramidal cell layer of the hippocampus in adults with Down's syndrome that these structures are significantly smaller than those found in control subjects. This is likely to be largely due to congenital malformation. The observation is supported by the fact that these structures in a Down's fetus were not so well formed as in a non-Down's fetus of equivalent age. Significant functional repercussion in memory processes and intellectual potential as well as in risk of developing ageing disease may follow hippocampal maldevelopment.