Whether or not a competitor stands on the podium wearing an Olympic metal can depend on a thousandth of a second difference in finishing time.  Greater physical performance may not be what separate winners from losers when the margin is that close.  Instead, it can be something beyond the competitor’s will–brainwaves.

Springing from the starting blocks too late can mean failure to metal, but jumping the gun results in disqualification.   What happens inside the brain in the roughly 1-2 tenths of a second reaction to hearing the starting pistol is an extremely complex process.  Rapid sensory perception to detect the starting signal, massive information processing to launch a wide-spread response throughout the brain, and rapid execution of precise motor commands, are all carried out unconsciously–faster than the speed of thought.

An invisible but important factor controlling complicated sensory-motor responses is brainwaves.  Brainwaves are oscillations in activity of millions of neurons taking place over large areas of the cerebral cortex.  The waves result from the combined activity of large populations of neurons that generate fluctuations in the electrical field in the surrounding brain tissue.  These voltage surges can oscillate locally or sweep across large territories of the brain, but they can be picked up by electrodes placed on the scalp.   Waves of electrical activity sweep through the brain at different frequencies like ripples, waves, and tides in a harbor all happening simultaneously, but each one acting in response to different forces and with different effects.  Oscillations in the electric field of brain tissue help coordinate the firing of neurons in phase with each other, just as boats are rocked in synchrony by waves in a harbor.  That coordinated firing is critical for organizing and coupling information transmission across distant regions of the brain.  Like all waves, brainwaves interact constructively and destructively to filter, sort, and coordinate the flow of information in the brain.  Different brainwaves oscillate at different characteristic frequency bands from 1 Hz to several hundred Hz, named alpha through delta, like broadcasts from different radio stations operating in their own frequency band.

One of the most important brainwave frequency bands for controlling movements are mu waves.  These waves oscillate in the motor cortex at 7.5-12.5 Hz.  The motor cortex is a strip of cerebral cortex that runs roughly ear-to ear like a plastic headband.  Just before a movement is initiated, these mu waves are quashed, a process called desynchronization.  This sudden calming of mu waves is believed to reflect different circuits of motor neurons breaking pace with the larger group and starting to fire independently to execute specific motor commands to appropriate muscles.

But mu waves are themselves riding on top of slower brainwave oscillations, in the same way that windblown ripples oscillate on top of slower ocean swells.  These very slow oscillations in brain activity were once dismissed as artifacts caused by fluctuations in blood pressure, but think again.  Blood flow affects brain function and the brain affects the heartbeat.  Thus, there is an interactive mind-body loop between brain and heart, and both oscillate slowly together.  Although an athlete’s heartrate may be 65 beats per minute, when followed over several tens of minutes the heartrate will vary slightly, oscillating at about 0.1 Hz (one cycle every 10 sec).  These oscillations in blood flow affect the firing of neurons in the brain.  This is easy to understand if you consider what happens in the extreme, when blood pressure drops suddenly–we lose consciousness and faint.  Even the small periodic fluctuations in blood pressure to the brain cause neuron excitability in the cerebral cortex to oscillate in synch with 0.1 Hz oscillations in frequency of the heartbeat.

So as the swimmers are poised motionless and ready to leap into the pool, inside their brain  neuronal excitability in their cerebral cortex is slowly oscillating on a 0.1Hz cycle.  By chance, some competitors will be at the peak of the neuronal excitability wave when the starting pistol fires and others will be in the trough.  “This excitability cycle modulates the central mu rhythms,” says, Gert Pfurtscheller, a neuroscientist who specializes in brainwaves in motor control, working at the Graz University of Technology in Austria.  “It can be expected therefore, that there exists a relationship between the 0.1 Hz excitability cycle, the starting gun, and the race outcome,” he says.