New Leads for Understanding Down Syndrome

Nancy Lee Raitano

By Rachel Ewing

New brain-imaging research led by psychology prof Nancy Raitano Lee, PhD, and published in the journal Cerebral Cortex, could unlock answers about intellectual development in youths with Down syndrome. It could also provide new insight into why individuals with this genetic neurodevelopmental disorder are more likely to develop early onset Alzheimer’s disease than the general population.

The cerebral cortex is the outer layer of brain tissue, a folded region about 2–4 millimeters thick, which is involved in important brain functions including sensory and cognitive processes. Lee’s study found that the cortex is thicker on average in youths with Down syndrome than in typically developing youths, even though the overall volume of the cortex is lower in those with Down syndrome.

Though the cause of the increased cortical thickness is still uncertain, one possibility is that the brains of those with Down syndrome do not prune excess neural connections as effectively as in typical development, a process believed to occur during childhood and young adulthood as part of reaching cognitive maturity.

Lee’s research also noted particularly pronounced differences in the cortex of youths with Down syndrome in several brain regions thought to belong to the Default Mode Network (DMN), the part of the brain that is active when a person is at rest. Because deterioration in the DMN has been associated with Alzheimer’s disease, Lee says these differences could provide clues about the early neural underpinnings of Alzheimer’s susceptibility in this group.

Surprisingly little is currently known about childhood brain development in those with Down syndrome. Lee hopes her finding will highlight the importance of the cortex for understanding developmental processes in this condition and spur further research. Such studies could more clearly illustrate how genetic abnormalities cause brain abnormalities — knowledge that could inform potential biomedical treatment approaches for intellectual disability.

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