A few weeks ago, there was some discussion on the Einstein-Syndrome list regarding statements made by the Changing Minds Foundation regarding the loss of neurons.
Because of this quote (namely the bolded portion) from the CMF website,
I did some researching and wrote up a response to this, which I thought I would share below. From what I recall, CMF did change some of the wording on their site to make sure there was no confusion.
"Problem: Loss of neurons in the hippocampus: Down syndrome loses 50% of their neuronal structure by 6 months old. This is an insurmountable problem.The University Of Maryland School Of Medicine treated Down syndrome mice with prozac for 24 days (2006). It increased neurogenesis (the formation of new nerves) to a normal level. This is like increasing the hardware on your computer. It allows you to run more complicated software. In fetuses with Down syndrome, neurons fail to show normal dendritic development, yielding a "tree in winter" appearance. This developmental failure is thought to result in mental retardation.""