Random neuronal firings cause mistakes

Scientists report that spontaneous brain activity, bursts of electrical noise in our neurons, may be what causes people to sometimes screw up simple physical tasks. For example, basketball players who miss an easy shot may be able to rightly blame these fluctuations. Researchers at Washington University scanned the brains of volunteers while playing a simple game where they pushed a button in response to an on-screen cue. From New Scientist:

As expected, the brain scans revealed increased activity within the left motor cortex – the region associated with controlling movement of the right hand – shortly after each button-pushing prompt.

Fox and colleagues also monitored spontaneous activity within the left motor cortex by analysing its "mirror image" in the right motor cortex. This allowed them to see how spontaneous brain activity affected each button press, independent of the "task-related" brain signals.

The researchers found that volunteers pressed the button with about half the force, on average, if spontaneous activity occurred a few seconds before each prompt.