Each time we perform a simple task, like pushing an elevator button or reaching for a cup of coffee, the brain races to decide whether the left or right hand will do the job. The left hand is more likely to win if a certain region of the brain receives magnetic stimulation, according to new research from the University of California (UC), Berkeley.
UC Berkeley researchers applied transcranial magnetic stimulation (TMS) to the posterior parietal cortex region of the brain in 33 right-handed volunteers and found that stimulating the left side spurred an increase in their use of the left hand, according to a press release.
With sensors on their fingertips, the study’s participants were instructed to reach for various targets on a virtual tabletop while a 3-D motion-tracking system followed the movements of their hands. When the left posterior parietal cortex was stimulated, and the target was located in a spot where they could use either hand, there was a significant increase of the use of the left hand, Oliveira said.
The left hemisphere of the brain controls the motor skills of the right side of the body and vice versa. By stimulating the parietal cortex, which plays a key role in processing spatial relationships and planning movement, the neurons that govern motor skills were disrupted.
“You’re handicapping the right hand in this competition, and giving the left hand a better chance of winning,” Flavio Oliveira, a UC Berkeley postdoctoral researcher in psychology and neuroscience and lead author of the study, stated in the release.
The findings challenge previous assumptions about how we make decisions, revealing a competitive process, at least in the case of manual tasks. Moreover, it shows that TMS can manipulate the brain to change plans for which hand to use, paving the way for clinical advances in the rehabilitation of victims of stroke and other brain injuries.
“By understanding this process, we hope to be able to develop methods to overcome learned limb disuse,” Richard Ivry, UC Berkeley professor of psychology and neuroscience and co-author of the study, stated.