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Brain disorders, such as Down syndrome, which is the most common type of hereditary intellectual disability, are some of the hardest conditions to understand. There are multiple mechanisms and levels of activity that occur in the brain that make it difficult to pinpoint the exact relationships between genetic mutations and the symptoms they cause. In Down syndrome people, in particular, researchers know that the condition results from an extra copy of a single chromosome. Researchers do not know how this one copy could result in a wide range of symptoms. In an attempt to understand this, researcher Anita Bhattacharyya, a neuroscientist at the Waisman Center at the University of Wisconsin-Madison, studied brain cells that were created from the skin cells of people with Down syndrome.

"Even though Down syndrome is very common, it's surprising how little we know about what goes wrong in the brain. These new cells provide a way to look at early brain development," she explained.

The research team looked at Down syndrome stem cells and neurons that were developed from the skin cells of people with the disorder. The team noted that the genes specific to the extra chromosome were increased by 150 percent. The team found that there was a reduction in the number of connections among the neurons. This reduction in connections, also known as synapses, indicates less communication happening in the brain. The researchers believe that it is the early lack of synapses that stunt brain development during early development and result in symptoms related to learning.

The team also found changes in these affected genes of Down syndrome neurons and stem cells. The most common change was how the genes responded to oxidative stress. Oxidative stress has been linked to causing several symptoms associated with Down syndrome.

"We definitely found a high level of oxidative stress in the Down syndrome neurons. This has been suggested before from other studies, but we were pleased to find more evidence for that. We now have a system we can manipulate to study the effects of oxidative stress and possibly prevent them," Bhattacharyya said.

Although the researchers were able to confirm previous findings, a lot more research needs to be done before researchers can find ways of potentially blocking certain Down syndrome symptoms.

The study was published in the Proceedings of the National Academy of Sciences.