Frontier: Broken Wiring

by Rabiya S. Tuma

July, 2006

Older individuals with mild cognitive impairment that includes memory problems are much more likely to develop Alzheimer’s disease than are their healthy peers. In a paper published June 27 in Proceedings of the National Academy of Sciences, Leyla deToledo-Morrell from Rush University Medical Center in Chicago and colleagues report that not only has the hippocampus, which is responsible for memory formation, atrophied in these patients, but the wiring inputs from the sensory processing regions of the brain have deteriorated as well.

The researchers used high-resolution imaging to measure the brain anatomy of 40 patients with mild cognitive impairment and 50 age-matched controls. As expected from previous work, they saw that the hippocampus was smaller in the patients with mild cognitive impairment. They also found that axon bundles that carry sensory information to the hippocampus, called the perforant path, were significantly reduced in patients. The more physical deterioration a patient had, the worse their memory function was.

“The hippocampus is not functioning well in these patients, but at the same time information is not coming into the hippocampus properly. So it is like a double whammy,” says deToledo-Morrell.

Understanding what is going wrong in the brains of patients with mild cognitive impairment will not help scientists stop progression of the disease right now, but as researchers test new therapies, they will know where to look for whether the treatments slow or repair the damage.