Because of the spontaneous brain activity
Now we know why even Ronaldinho or Shaq can miss easy shots: spontaneous fluctuations of brain’s electrical activity are to blame. A team at Washington University, in Missouri, US, discovered that fluctuations in the brain activity made subjects to subconsciously exert a little less physical power when pushing a button on cue. This was not linked to any external stimulus, attention or anticipation and it is the first direct proof that internal instabilities (“spontaneous brain activity”) could be behind the variability of human behavioral responses.
Brain-scanning techniques have been uncovering for almost two decades variable brain activity not connected to external stimuli while a person is asleep or anesthetized, but the way these fluctuations in neuronal network affects behavior has been difficult to assess.
To check this, a team led by Michael Fox at Washington University made an experiment in which the brains of 17 subjects were monitored through functional magnetic resonance imaging (fMRI) as they performed a simple finger-tapping task.
The subjects had to push a button with their right hand when seeing an on-screen prompt. The team focused on the timing and force of each button press. Increased activity was detected within the left motor cortex (the brain area connected with movement control of the right hand) soon after each button-pushing prompt. The team also monitored spontaneous activity within the left motor cortex by observing its “mirror image” in the right motor cortex, a fact that permitted them to assess the way spontaneous brain activity influenced each button press, out of the “task-related” brain impulses.
The subjects were found to press the button with an average 50 % of the force if spontaneous activity took place a few seconds before each prompt.
“This is the first clear evidence that [spontaneous brain activity] has some behavioral significance,” said Rasmus Birn of the National Institute of Health in Maryland, US, not involved with the study.
“It remains unclear how spontaneous activity in the motor cortex might cause people to tap their fingers more gently, but it could be because the activity fools the brain into thinking the finger has already moved partly towards the button.” said Fox.
The team points out that the spontaneous brain activity could explain why you miss a shot that was apparently an easy goal or basket, by affecting the force you put on the kick or ball throw.
Still, “it remains to be seen whether this result holds for more complex cognitive tasks or other brain regions or networks”, Birn concludes.