Science Daily goes deep, deep into our innermost selves and reveals what a brain looks like the moment a mind changes:
The findings result from experiments led by electrical engineering Professor Krishna Shenoy, whose Stanford lab focuses on movement control and neural prostheses — such as artificial arms — controlled by the user’s brain.
“This basic neuroscience 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,” Shenoy said.
The experiments are described in the journal eLife. They 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.
During the experiments, 192 electrodes in each monkey’s motor and premotor cortex began measuring brain activity the moment that the targets appeared on screen. The measurements continued until the targets stopped jittering and the monkey began to move. The interval between the targets’ appearance and the beginning of movement marked the time of decision or, in some cases, hesitation.
“We can now track single decisions with unprecedented precision,” Kaufman said. “We saw that the brain activity for a typical free choice looked just like it did for a forced choice. But a few of the free choices were different. Occasionally, he was indecisive for a moment before he made any plan at all. About one time in eight, he made a plan quickly but spontaneously changed his mind a moment later.”
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.
Kaufman said the team’s findings also bear on a longstanding philosophical debate about human consciousness.
In the early 1980s, University of California, San Francisco neuroscientist Benjamin Libet conducted an experiment to assess the nature of free will. Subjects hooked up to an electroencephalogram (EEG) were asked to push a button whenever they liked. They were also asked to note the precise time that they first became aware of the wish or urge to move.
Libet’s experiments showed that distinctive brain activity began, on average, several seconds before subjects became aware that they planned to move.