Now, researchers from BU (Boston University) and MIT have explained how neural groups shape thoughts and assist the adaptability of making decisions and the ability to change how we feel about certain things.
The experts, led by Earl Miller, the Picower Professor of Neuroscience at MIT, have found neuron clusters which encode precise behavioral rules by swinging back and forth simultaneously with each other.
The recent trial, which was published in the journal Neuron, indicated that makeup of conscious thought could possibly be rhythmic.
"As we talk, thoughts float in and out of our heads. Those are all emsembles forming and then reconfiguring to something else. It's been a mystery how the brain does this. That's the fundamental problem that we're talking about - the very nature of thought itself."
Scientists found two neural groups in monkey brains, who were trained to show response to objects due to either either orientation or color, a duty which demands cognitive flexibility - the capability to shift back and forth between two different series of behavioral rules.
Tim Buschman, an MIT postdoc and one of the lead authors of the study, said, "Effectively what they're doing is focusing on some parts of information in the world and ignoring others. Which behavior they're doing depends on the context."
When the monkeys were changing tasks, the experts analyzed brain waves made in different parts of the prefrontal cortex, the area where the majority of thought and planning occurs. These waves are prompted by rhythmic changes of neurons' electrical activity.
When the animals reacted to the objects based on orienation, the scientists discovered that distinct neurons swayed back and forth at high frequencies which resulted in the formation of beta waves. When the monkeys reacted to color, a different group of neurons oscillated in the beta frequency. Certain neurons were found to belong in more than one group, however, each one has its own specific pattern.
The experts note that they found oscillations in the low-frequency alpha range in neurons which the rule ensemble is composed of, however, solely when the color rule was in effect. They think that the alpha waves, which have previously been linked with brain activity suppression, assist in silencing the neurons which prompt the orientation rule.
Miller said, "What this suggests is that orientation was dominant, and color was weaker. The brain was throwing this blast of alpha at the orientation ensemble to shut it up, so the animal could use the weaker ensemble."
Scientists are now trying to reveal how the neural ensembles organize their activity while the brain changes back and forth between certain rules and thoughts. "It's one of the biggest mysteries of cognition, what controls your thoughts," said Miller.
He said, "The most fundamental characteristic of consciousness is its limited capacity. You can only hold a very few thoughts in mind simultaneously." Prior studies have determined that when an animal is thinking two thoughts at once, two separate ensembles oscillate in beta frequencies, not in sync with one another.
"That immediately suggests why there's a limited capacity to consciousness: Only so many balls can be kept in the air at the same time, only a limited amount of information can fit into one oscillatory cycle."
Written by Christine Kearney