Brain connections break down as we age

It's unavoidable: breakdowns in brain connections slow down our physical response times as we age, a new study suggests.

The circled portion of the older adult' brain on the left indicates the cross-talk between the two hemispheres that is not apparent in the younger brain on the right. Provided by Rachael Seidler

This slower reactivity is associated with an age-related breakdown in the corpus callosum, a part of the brain that acts as a dam during one-sided motor activities to prevent unwanted connectivity, or cross-talk, between the two halves of the brain, said Rachael Seidler, associate professor in the University of Michigan School of Kinesiology and Department of Psychology, and lead study author.

At other times the corpus callosum acts at a bridge and cross-talk is helpful, such as in certain cognitive functions or two-sided motor skills.

The University of Michigan study is the first known to show that this cross-talk happens even while older adults are at rest, said Seidler, who also has appointments in the Institute of Gerontology and the Neuroscience Graduate Program.

This resting cross-talk suggests that it is not helpful or compensatory for the two halves of the brain to communicate during one-sided motor movements because the opposite side of the brain controls the part of the body that is moving. So, when both sides of the brain talk simultaneously while one side of the body tries to move, confusion and slower responses result, Seidler said.

Previous studies have shown that cross-talk in the brain during certain motor tasks increases with age but it wasn't clear if that cross-talk helped or hindered brain function, said Seidler.