Change of mind observed in real-time

In a first such experiment, Indian-American scientist Krishna Shenoy and his team from Stanford University have recorded the moment-by-moment fluctuations in brain signals that occur when a monkey making free choices has a change of mind.

The findings result from experiments that focused on movement control and neural prostheses - such as artificial arms - controlled by the user's brain.

"This discovery will help create neural prostheses that can withhold moving a prosthetic arm until the user is certain of their decision, thereby averting premature or inopportune movements," said Shenoy, professor of electrical engineering.

The experiments were performed by neuroscientist Matthew Kaufman while he was a graduate student in Shenoy's lab.

Kaufman taught laboratory monkeys to perform a decision-making task.

He then developed a technique to track the brain signals that occur during a single decision with split-second accuracy.

This improvement on what's called the "single trial decoder" algorithm revealed the neural signals that occurred during a momentary hesitation or when the monkey changed his mind.

"We are seeing many cognitive phenomena in the brain for the first time," said Kaufman who is now a post-doctoral scholar at Cold Spring Harbor Laboratory.

"The most critical result of our work here is that we can track a single decision and see how the monkey arrived there: whether he decided quickly, slowly, or changed his mind halfway through," he informed.

The experiments involved monkeys that were trained to reach for either of two targets on a computer screen. It was often possible to reach either target, inviting a free choice.

Sometimes one target was blocked, resulting in a forced choice.

Other times, the researchers would switch between these configurations while the monkey was deciding, encouraging a change of mind.

The research focused on the time the monkey spent deliberating, before the actual movement began.

The monkeys were trained to sit motionless while two jittering targets were positioned on either side of a computer screen.

Using his single-trial decoder algorithm, the team analysed moment-by-moment brain activity during each individual decision.

In a sense, they was able to read the monkey's mind during free choices, when each decision may be different.

This deeper understanding of decision-making will help researchers to fine-tune the control algorithms of neural prostheses to enable people with paralysis to drive a brain-controlled prosthetic arm or guide a neurally-activated cursor on a computer screen.

The team's findings also bear on a long-standing philosophical debate about human consciousness.

The experiments were described in the journal eLife.