While eating lunch you notice an insect buzzing around your plate. Its color and motion could both influence how you respond. If the insect was yellow and black you might decide it was a bee and move away. Conversely, you might simply be annoyed at the buzzing motion and shoo the insect away. You perceive both color and motion, and decide based on the circumstances. Our brains make such contextual decisions in a heartbeat. The mystery is how.
In an article published November 7th in the journal Nature, a team of Stanford neuroscientists and engineers delve into this decision-making process and report some findings that confound the conventional wisdom.
Until now, neuroscientists have believed that decisions of this sort involved two steps: one group of neurons that performed a gating function to ascertain whether motion or color was most relevant to the situation, and a second group of neurons that considered only the sensory input relevant to making a decision under the circumstances.
But in a study that combined brain recordings from trained monkeys, and a sophisticated computer model based on that biological data, Stanford neuroscientist William Newsome and three coauthors discovered that the entire decision-making process may occur in a localized region of the prefrontal cortex.
In this region of the brain, located in the frontal lobes just behind the forehead, they found that color and motion signals converged in a specific circuit of neurons. Based on their experimental evidence and computer simulations, the scientists hypothesized that these neurons act together to make two snap judgments: is color or motion the most relevant sensory input in the current context, and what action to take as a result.
"We were quite surprised," said Newsome, the Harman Family Provostial Professor at the Stanford School of Medicine and lead author.
He and first author Valerio Mante, a former Stanford neurobio
|Contact: Tom Abate|
Stanford School of Engineering