Even when brain shrinks with age, cells' density remains constant

A new study has revealed that cell density remains constant even though the brain shrinks with age.

New, ultra-high-field magnetic resonance images (MRI) of the brain by researchers at the University of Illinois at Chicago provided the most detailed images to date to show that while the brain shrinks with age, brain cell density remains constant.

The images provide the first evidence that in normal aging, cell density is preserved throughout the brain, not just in specific regions, as previous studies on human brain tissue have shown. The findings also suggested that the maintenance of brain cell density may protect against cognitive impairment as the brain gradually shrinks in normal aging.

The images were made at UIC by a powerful 9.4-Tesla MRI, the first of its kind for human imaging. The 9.4 T magnetic field is more than three times stronger than that of a typical MRI machine in a doctor's office and is currently approved only for research. The strongest MRI units approved for clinical use are 3 T.

Dr. Keith Thulborn, director of MRI research in the UIC College of Medicine, said that the information provided by these 9.4-Tesla scans might be very useful in detecting tiny losses of brain cells and the reduction in cell density that characterizes the early stages of neurodegenerative diseases that can take decades to develop before symptoms appear, like Alzheimer's disease.

Neuroscientists have long known that the brain shrinks with age, but for a long time they thought the loss in volume was associated with a loss of brain cells. That was disproven by studies that showed it is the neurons themselves that shrink while the number of cells remains the same in normal older adults.

The study is published in the journal NMR in Biomedicine.