For sports fans, the first week of the London Olympics has delivered a spectacular spectrum of sports competition. For sports performance and human movement scientists, the Summer Games are a live laboratory for their theories and research. Whether it’s watching the record-setting swimming strokes of Michael Phelps or the acrobatic gymnastic routines of Gabby Douglas, kinesiologists have been stumped to explain exactly how the human brain instructs the body to perform such advanced movements. Last month, researchers at Stanford, Columbia and Cambridge Universities released a study that proposes a very different theory of how this brain-body communication takes place.
For years, cognitive scientists used what we knew about our visual system to also explain how our motor cortex, the part of the brain that controls movement, delivers messages to our muscles. In the visual cortex, it is known that the specific data from the outside world, such as objects, colors, spatial location, are tracked by individual neurons.
“Visual neurons encode things in the world. They are a map, a representation,” said John Cunningham, PhD and co-lead author of the new study. “It’s not a leap to imagine that neurons in the motor cortex should behave like neurons in the visual cortex, relating in a faithful way to external parameters, but things aren’t so concrete for movement.”
That same mapping for movement to neurons has never been confirmed. “We just couldn’t look at an arm movement and use that to reliably predict what individual neurons in the motor cortex had been doing to produce that movement,” Cunningham said.
Cunningham’s team of electrical engineers and brain experts created a unique experiment that tracked the movements of monkeys as they reached out to touch lit target buttons. By watching the neuro signals and patterns, a surprising but logical rhythmic sequence emerged.
“Finding these brain rhythms surprised us a bit, as the reaches themselves were not rhythmic. In fact, they were decidedly arrhythmic, and yet underlying it all were these unmistakable patterns,” said Mark Churchland, PhD, who was a postdoctoral researcher at Stanford at the time of the study and is now assistant professor of neuroscience at Columbia University. “The brain has had an evolutionary goal to drive movements that help us survive. The primary motor cortex is key to these functions. The patterns of activity it displays presumably derive from evolutionarily older rhythmic motions such as swimming and walking. Rhythm is a basic building block of movement.”
So, much like a band of musicians playing different parts to a song, the mix of rhythms combines to produce a song. The visual cortex provides the external data needed to plan just the right mix of movements on a second by second basis but then this pattern of rhythms actually executes the command.
“Say you’re throwing a ball. Beneath it all is a pattern. Maybe your shoulder muscle contracts, relaxes slightly, contracts again, and then relaxes completely, all in short order,” explained Churchland. “That activity may not be exactly rhythmic, but it can be created by adding together two or three other rhythms. Our data argue that this may be how the brain solves the problem of creating the pattern of movement.”
Much is left to learn, but this breakthrough will help future research not only for athletes but also for advances in the use of prosthetic limbs. In the meantime, it makes both fans and performance specialists appreciate the incredible skills that we’ve seen at the London games.