As We Age, Loss of Brain Connections Slows Our Reaction Time
Have you ever wondered why kids seem so much better at video games than adults? A University of Michigan study suggests that, as we age, our brain connections break down, slowing up our physical response times.
According to the study, older adults seem to have excessive ‘cross-talk’ between the two hemispheres of the brain. This cross-communication occurs through a brain structure called the corpus callosum, which can act as either a bridge or a dam between brain hemispheres.
The bridge action is very important during two-sided motor skills and certain cognitive functions. However, during one-sided motor skills requiring strong focus from only one side, the corpus callosum switches roles and serves as a sort of dam between hemispheres.
As we age, breakdowns in the corpus callosum occur, breaking down the dam effect, and causing more cross-talk to occur between hemispheres, even when it’s not particularly useful.
The study is the first known to show that this cross-talk happens even while older adults are at rest, says Rachael Seidler, lead study author and associate professor in the University of Michigan School of Kinesiology and department of psychology.
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 says.
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, says Seidler.
“Cross-talk is not a function of task difficulty, because we see these changes in the brain when people are not moving,” adds Seidler.
In some diseases where the corpus callosum is very deteriorated, such as in multiple sclerosis, a person will have “mirror movements” during one sided-motor tasks, in which both sides of the body move in concert because there is too much communication between the two hemispheres of the brain, Seidler says. These mirror movements can also be seen in very young children before the corpus callosum is fully developed.
During the study, scientists gave joysticks to adults between the ages of 65 and 75 and measured and compared their response times against a group approximately 20 to 25 years old.
Researchers then used a functional MRI to image the blood-oxygen levels in different parts of the brain, a measurement of brain activity.
“The more they recruited the other side of the brain, the slower they responded,” Seidler says.
Researchers believe there is hope, however, and just because we all get older, it doesn’t have to be our fate to react slowly. Seidler and her colleagues are developing and piloting motor training studies that might rebuild or maintain the corpus callosum to limit overflow between hemispheres, she said.
A previous study done by another group showed that doing aerobic training for three months helped to rebuild the corpus callosum, she said, which suggests that physical activity can help to counteract the effects of the age-related degeneration.
Seidler’s group also has a study in review that uses the same brain imaging techniques to examine disease-related brain changes in Parkinson’s patients.
The study appeared in the journal Frontiers in Systems Neuroscience.
Pedersen, T. (2010). As We Age, Loss of Brain Connections Slows Our Reaction Time. Psych Central. Retrieved on April 18, 2015, from http://psychcentral.com/news/2010/09/13/as-we-age-loss-of-brain-connections-slows-our-reaction-time/18031.html